Alfred Frontera, MD

Subacute combined degeneration (SCD) is an acquired neurologic complication of vitamin B12 (cobalamin) or, rarely, vitamin B9 (folate) deficiency. SCD is characterized by progressive demyelination of the dorsal and lateral spinal cord, resulting in peripheral neuropathy; gait ataxia; impaired proprioception, vibration, and fine touch; optic neuropathy; and cognitive impairment.¹ In addition to SCD, other neurologic manifestations of B12 deficiency include dementia, depression, visual symptoms due to optic atrophy, and behavioral changes.² The prevalence of SCD in the US has not been well documented, but B12 deficiency is reported at 6% in those aged < 60 years and 20% in those > 60 years^.3

Causes of B12 and B9 deficiency include advanced age, low nutritional intake (eg, vegan diet), impaired absorption (eg, inflammatory bowel disease, autoimmune pernicious anemia, gastrectomy, pancreatic disease), alcohol use, tapeworm infection, medications, and high metabolic states.^2,4 Impaired B12 absorption is common in patients taking medications, such as metformin and proton pump inhibitors (PPI), due to suppression of ileal membrane transport and intrinsic factor activity.^5-7 B-vitamin deficiency can be exacerbated by states of increased cellular turnover, such as polycythemia vera, due to elevated DNA synthesis.

Patients may experience permanent neurologic damage when the diagnosis and treatment of SCD are missed or delayed. Early diagnosis of SCD can be challenging due to lack of specific hematologic markers. In addition, many other conditions such as diabetic neuropathy, malnutrition, toxic neuropathy, sarcoidosis, HIV, multiple sclerosis, polycythemia vera, and iron deficiency anemia have similar presentations and clinical findings.⁸ Anemia and/or macrocytosis are not specific to B12 deficiency.⁴ In addition, patients with B12 deficiency may have a normal complete blood count (CBC); those with concomitant iron deficiency may have minimal or no mean corpuscular volume (MCV) elevation.⁴ In patients suspected to have B12 deficiency based on clinical presentation or laboratory findings of macrocytosis, serum methylmalonic acid (MMA) can serve as a direct measure of B12 activity, with levels > 0.75 μmol/L almost always indicating cobalamin deficiency. ⁹ On the other hand, plasma total homocysteine (tHcy) is a sensitive marker for B12 deficiency. The active form of B12, holotranscobalamin, has also emerged as a specific measure of B12 deficiency.⁹ However, in patients with SCD, measurement of these markers may be unnecessary due to the severity of their clinical symptoms. 

The diagnosis of SCD is further complicated because not all individuals who develop B12 or B9 deficiency will develop SCD. It is difficult to determine which patients will develop SCD because the minimum level of serum B12 required for normal function is unknown, and recent studies indicate that SCD may occur even at low-normal B12 and B9 levels.^2,4,10 Commonly, a serum B12 level of < 200 pg/mL is considered deficient, while a level between 200 and 300 pg/mL is considered borderline.⁴ The goal level of serum B12 is > 300 pg/mL, which is considered normal.⁴ While serologic findings of B-vitamin deficiency are only moderately specific, radiographic findings are highly sensitive and specific for SCD. According to Briani and colleagues, the most consistent finding in SCD on magnetic resonance imaging (MRI) is a “symmetrical, abnormally increased T2 signal intensity, commonly confined to posterior or posterior and lateral columns in the cervical and thoracic spinal cord.”²

We present a case of SCD in a patient with low-normal vitamin B12 levels who presented with progressive sensorimotor deficits and vision loss. The patient was subsequently diagnosed with SCD by radiologic workup. His course was complicated by worsening neurologic deficits despite B12 replacement. The progression of his clinical symptoms demonstrates the need for prompt, aggressive B12 replacement in patients diagnosed with SCD.

Case Presentation

A 63-year-old man presented for neurologic evaluation of progressive gait disturbance, paresthesia, blurred vision, and increasing falls despite use of a walker. Pertinent medical history included polycythemia vera requiring phlebotomy for approximately 9 years, alcohol use disorder (18 servings weekly), type 2 diabetes mellitus, and a remote episode of transient ischemic attack (TIA). The patient reported a 5-year history of burning pain in all extremities. A prior physician diagnosis attributed the symptoms to polyneuropathy secondary to iron deficiency anemia in the setting of chronic phlebotomy for polycythemia vera and high erythrogenesis. He was prescribed gabapentin 600 mg 3 times daily for pain control. B12 deficiency was considered an unlikely etiology due to a low-normal serum level of 305 pg/mL (reference range, 190-950 pg/mL) and normocytosis, with MCV of 88 fL (reference range, 80-100 fL). The patient also reported a 3-year history of blurred vision, which was initially attributed to be secondary to diabetic retinopathy. One week prior to presenting to our clinic, he was evaluated by ophthalmology for new-onset, bilateral central visual field defects, and he was diagnosed with nutritional optic neuropathy.

Previous cardiac evaluation failed to provide a diagnosis for syncopal episodes. MRI of the brain revealed nonspecific white matter changes consistent with chronic microvascular ischemic disease. Electromyography was limited due to pain but showed severe peripheral neuropathy. Laboratory results showed megalocytosis, low-normal serum B12 levels, and low serum folate levels (Table 2). The patient was diagnosed with polyneuropathy and was given intramuscular (IM) vitamin B12 1000 mcg once and a daily multivitamin (containing 25 mcg of B12). He was counseled on alcohol abstinence and medication adherence and was scheduled for follow-up in 3 months. He continued outpatient phlebotomy every 6 weeks for polycythemia.

At 3-month follow-up, the patient reported medication adherence, continued alcohol use, and worsening of symptoms. Falls, which now occurred 2 to 3 times weekly despite proper use of a walker, were described as sudden loss of bilateral lower extremity strength without loss of consciousness, palpitations, or other prodrome. Laboratory results showed minimal changes. Physical examination of the patient demonstrated similar deficits as on initial presentation. The patient received one additional B12 1000 mcg IM. Gabapentin was replaced with pregabalin 75 mg twice daily due to persistent uncontrolled pain and paresthesia. The patient was scheduled for a 3-month followup (6 months from initial visit) and repeat serology.

At 6-month follow-up, the patient showed continued progression of disease with significant difficulty using the walker, worsening falls, and wheelchair use required. Physical examination showed decreased sensation bilaterally up to the knees, absent bilateral patellar and Achilles reflexes, and unsteady gait. Laboratory results showed persistent subclinical B12 deficiency. MRI of the brain and spine showed high T2 signaling in a pattern highly specific for SCD. A formal diagnosis of SCD was made. The patient received an additional B12 1000 mcg IM once. Follow-up phone call with the patient 1 month later revealed no progression or improvement of symptoms.

Radiographic Findings

MRI of the cervical and thoracic spine demonstrated abnormal high T2 signal starting from C2 and extending along the course of the cervical and thoracic spinal cord (Figure). MRI in SCD classically shows symmetric, bilateral high T2 signal within the dorsal columns; on axial images, there is typically an inverted “V” sign.^2,4 There can also be abnormal cerebral white matter change; however, MRI of the brain in this patient did not show any abnormalities.2 The imaging differential for this appearance includes other metabolic deficiencies/toxicities: copper deficiency; vitamin E deficiency; methotrexateinduced myelopathy, and infectious causes: HIV vacuolar myelopathy; and neurosyphilis (tabes dorsalis).⁴

Discussion

This case demonstrates the clinical and radiographic findings of SCD and underscores the need for high-intensity dosing of B12 replacement in patients with SCD to prevent progression of the disease and development of morbidities.

Symptoms of SCD may manifest even when the vitamin levels are in low-normal levels. Its presentation is often nonspecific, thus radiologic workup is beneficial to elucidate the clinical picture. We support the use of spinal MRI in patients with clinical suspicion of SCD to help rule out other causes of myelopathy. However, an MRI is not indicated in all patients with B12 deficiency, especially those without myelopathic symptoms. Additionally, follow-up spinal MRIs are useful in monitoring the progression or improvement of SCD after B12 replacement.² It is important to note that the MRI findings in SCD are not specific to B12 deficiency; other causes may present with similar radiographic findings.⁴ Therefore, radiologic findings must be correlated with a patient’s clinical presentation.

B12 replacement improves and may resolve clinical symptoms and abnormal radiographic findings of SCD. The treatment duration of B12 deficiency depends on the underlying etiology. Reversible causes, such as metformin use > 4 months, PPI use > 12 months, and dietary deficiency, require treatment until appropriate levels are reached and symptoms are resolved.^4,11 The need for chronic metformin and PPI use should also be reassessed regularly. In patients who require long-term metformin use, IM administration of B12 1000 mcg annually should be considered, which will ensure adequate storage for more than 1 year.^12,13 In patients who require long-term PPI use, the risk and benefits of continued use should be measured, and if needed, the lowest possible effective PPI dose is recommended.¹⁴ Irreversible causes of B12 deficiency, such as advanced age, prior gastrectomy, chronic pancreatitis, or autoimmune pernicious anemia, require lifelong supplementation of B12.^4,11

In general, oral vitamin B12 replacement at 1000 to 2000 mcg daily may be as effective as parenteral replacement in patients with mild to moderate deficiency or neurologic symptoms.¹¹ On the other hand, patients with SCD often require parenteral replacement of B12 due to the severity of their deficiency or neurologic symptoms, need for more rapid improvement in symptoms, and prevention of irreversible neurological deficits. ^4,11 Appropriate B12 replacement in SCD requires intensive initial therapy which may involve IM B12 1000 mcg every other day for 2 weeks and additional IM supplementation every 2 to 3 months afterward until resolution of deficiency.^4,14 IM replacement may also be considered in patients who are nonadherent to oral replacement or have an underlying gastrointestinal condition that impairs enteral absorption.^4,11

B12 deficiency is frequently undertreated and can lead to progression of disease with significant morbidity. The need for highintensity dosing of B12 replacement is crucial in patients with SCD. Failure to respond to treatment, as shown from the lack of improvement of serum markers or symptoms, likely suggests undertreatment, treatment nonadherence, iron deficiency anemia, an unidentified malabsorption syndrome, or other diagnoses. In our case, significant undertreatment, compounded by his suspected iron deficiency anemia secondary to his polycythemia vera and chronic phlebotomies, are the most likel etiologies for his lack of clinical improvement.

Multiple factors may affect the prognosis of SCD. Males aged < 50 years with absence of anemia, spinal cord atrophy, Romberg sign, Babinski sign, or sensory deficits on examination have increased likelihood of eventual recovery of signs and symptoms of SCD; those with less spinal cord involvement (< 7 cord segments), contrast enhancement, and spinal cord edema also have improved outcomes.^4,15

Conclusion

SCD is a rare but serious complication of chronic vitamin B12 deficiency that presents with a variety of neurological findings and may be easily confused with other illnesses. The condition is easily overlooked or misdiagnosed; thus, it is crucial to differentiate B12 deficiency from other common causes of neurologic symptoms. Specific findings on MRI are useful to support the clinical diagnosis of SCD and guide clinical decisions. Given the prevalence of B12 deficiency in the older adult population, clinicians should remain alert to the possibility of these conditions in patients who present with progressive neuropathy. Once a patient is diagnosed with SCD secondary to a B12 deficiency, appropriate B12 replacement is critical. Appropriate B12 replacement is aggressive and involves IM B12 1000 mcg every other day for 2 to 3 weeks, followed by additional IM administration every 2 months before transitioning to oral therapy. As seen in this case, failure to adequately replenish B12 can lead to progression or lack of resolution of SCD symptoms.

Subacute combined degeneration (SCD) is an acquired neurologic complication of vitamin B12 (cobalamin) or, rarely, vitamin B9 (folate) deficiency. SCD is characterized by progressive demyelination of the dorsal and lateral spinal cord, resulting in peripheral neuropathy; gait ataxia; impaired proprioception, vibration, and fine touch; optic neuropathy; and cognitive impairment.¹ In addition to SCD, other neurologic manifestations of B12 deficiency include dementia, depression, visual symptoms due to optic atrophy, and behavioral changes.² The prevalence of SCD in the US has not been well documented, but B12 deficiency is reported at 6% in those aged < 60 years and 20% in those > 60 years^.3

Causes of B12 and B9 deficiency include advanced age, low nutritional intake (eg, vegan diet), impaired absorption (eg, inflammatory bowel disease, autoimmune pernicious anemia, gastrectomy, pancreatic disease), alcohol use, tapeworm infection, medications, and high metabolic states.^2,4 Impaired B12 absorption is common in patients taking medications, such as metformin and proton pump inhibitors (PPI), due to suppression of ileal membrane transport and intrinsic factor activity.^5-7 B-vitamin deficiency can be exacerbated by states of increased cellular turnover, such as polycythemia vera, due to elevated DNA synthesis.

Patients may experience permanent neurologic damage when the diagnosis and treatment of SCD are missed or delayed. Early diagnosis of SCD can be challenging due to lack of specific hematologic markers. In addition, many other conditions such as diabetic neuropathy, malnutrition, toxic neuropathy, sarcoidosis, HIV, multiple sclerosis, polycythemia vera, and iron deficiency anemia have similar presentations and clinical findings.⁸ Anemia and/or macrocytosis are not specific to B12 deficiency.⁴ In addition, patients with B12 deficiency may have a normal complete blood count (CBC); those with concomitant iron deficiency may have minimal or no mean corpuscular volume (MCV) elevation.⁴ In patients suspected to have B12 deficiency based on clinical presentation or laboratory findings of macrocytosis, serum methylmalonic acid (MMA) can serve as a direct measure of B12 activity, with levels > 0.75 μmol/L almost always indicating cobalamin deficiency. ⁹ On the other hand, plasma total homocysteine (tHcy) is a sensitive marker for B12 deficiency. The active form of B12, holotranscobalamin, has also emerged as a specific measure of B12 deficiency.⁹ However, in patients with SCD, measurement of these markers may be unnecessary due to the severity of their clinical symptoms. 

The diagnosis of SCD is further complicated because not all individuals who develop B12 or B9 deficiency will develop SCD. It is difficult to determine which patients will develop SCD because the minimum level of serum B12 required for normal function is unknown, and recent studies indicate that SCD may occur even at low-normal B12 and B9 levels.^2,4,10 Commonly, a serum B12 level of < 200 pg/mL is considered deficient, while a level between 200 and 300 pg/mL is considered borderline.⁴ The goal level of serum B12 is > 300 pg/mL, which is considered normal.⁴ While serologic findings of B-vitamin deficiency are only moderately specific, radiographic findings are highly sensitive and specific for SCD. According to Briani and colleagues, the most consistent finding in SCD on magnetic resonance imaging (MRI) is a “symmetrical, abnormally increased T2 signal intensity, commonly confined to posterior or posterior and lateral columns in the cervical and thoracic spinal cord.”²

We present a case of SCD in a patient with low-normal vitamin B12 levels who presented with progressive sensorimotor deficits and vision loss. The patient was subsequently diagnosed with SCD by radiologic workup. His course was complicated by worsening neurologic deficits despite B12 replacement. The progression of his clinical symptoms demonstrates the need for prompt, aggressive B12 replacement in patients diagnosed with SCD.

Case Presentation

A 63-year-old man presented for neurologic evaluation of progressive gait disturbance, paresthesia, blurred vision, and increasing falls despite use of a walker. Pertinent medical history included polycythemia vera requiring phlebotomy for approximately 9 years, alcohol use disorder (18 servings weekly), type 2 diabetes mellitus, and a remote episode of transient ischemic attack (TIA). The patient reported a 5-year history of burning pain in all extremities. A prior physician diagnosis attributed the symptoms to polyneuropathy secondary to iron deficiency anemia in the setting of chronic phlebotomy for polycythemia vera and high erythrogenesis. He was prescribed gabapentin 600 mg 3 times daily for pain control. B12 deficiency was considered an unlikely etiology due to a low-normal serum level of 305 pg/mL (reference range, 190-950 pg/mL) and normocytosis, with MCV of 88 fL (reference range, 80-100 fL). The patient also reported a 3-year history of blurred vision, which was initially attributed to be secondary to diabetic retinopathy. One week prior to presenting to our clinic, he was evaluated by ophthalmology for new-onset, bilateral central visual field defects, and he was diagnosed with nutritional optic neuropathy.

Previous cardiac evaluation failed to provide a diagnosis for syncopal episodes. MRI of the brain revealed nonspecific white matter changes consistent with chronic microvascular ischemic disease. Electromyography was limited due to pain but showed severe peripheral neuropathy. Laboratory results showed megalocytosis, low-normal serum B12 levels, and low serum folate levels (Table 2). The patient was diagnosed with polyneuropathy and was given intramuscular (IM) vitamin B12 1000 mcg once and a daily multivitamin (containing 25 mcg of B12). He was counseled on alcohol abstinence and medication adherence and was scheduled for follow-up in 3 months. He continued outpatient phlebotomy every 6 weeks for polycythemia.

At 3-month follow-up, the patient reported medication adherence, continued alcohol use, and worsening of symptoms. Falls, which now occurred 2 to 3 times weekly despite proper use of a walker, were described as sudden loss of bilateral lower extremity strength without loss of consciousness, palpitations, or other prodrome. Laboratory results showed minimal changes. Physical examination of the patient demonstrated similar deficits as on initial presentation. The patient received one additional B12 1000 mcg IM. Gabapentin was replaced with pregabalin 75 mg twice daily due to persistent uncontrolled pain and paresthesia. The patient was scheduled for a 3-month followup (6 months from initial visit) and repeat serology.

At 6-month follow-up, the patient showed continued progression of disease with significant difficulty using the walker, worsening falls, and wheelchair use required. Physical examination showed decreased sensation bilaterally up to the knees, absent bilateral patellar and Achilles reflexes, and unsteady gait. Laboratory results showed persistent subclinical B12 deficiency. MRI of the brain and spine showed high T2 signaling in a pattern highly specific for SCD. A formal diagnosis of SCD was made. The patient received an additional B12 1000 mcg IM once. Follow-up phone call with the patient 1 month later revealed no progression or improvement of symptoms.

Radiographic Findings

MRI of the cervical and thoracic spine demonstrated abnormal high T2 signal starting from C2 and extending along the course of the cervical and thoracic spinal cord (Figure). MRI in SCD classically shows symmetric, bilateral high T2 signal within the dorsal columns; on axial images, there is typically an inverted “V” sign.^2,4 There can also be abnormal cerebral white matter change; however, MRI of the brain in this patient did not show any abnormalities.2 The imaging differential for this appearance includes other metabolic deficiencies/toxicities: copper deficiency; vitamin E deficiency; methotrexateinduced myelopathy, and infectious causes: HIV vacuolar myelopathy; and neurosyphilis (tabes dorsalis).⁴

Discussion

This case demonstrates the clinical and radiographic findings of SCD and underscores the need for high-intensity dosing of B12 replacement in patients with SCD to prevent progression of the disease and development of morbidities.

Symptoms of SCD may manifest even when the vitamin levels are in low-normal levels. Its presentation is often nonspecific, thus radiologic workup is beneficial to elucidate the clinical picture. We support the use of spinal MRI in patients with clinical suspicion of SCD to help rule out other causes of myelopathy. However, an MRI is not indicated in all patients with B12 deficiency, especially those without myelopathic symptoms. Additionally, follow-up spinal MRIs are useful in monitoring the progression or improvement of SCD after B12 replacement.² It is important to note that the MRI findings in SCD are not specific to B12 deficiency; other causes may present with similar radiographic findings.⁴ Therefore, radiologic findings must be correlated with a patient’s clinical presentation.

B12 replacement improves and may resolve clinical symptoms and abnormal radiographic findings of SCD. The treatment duration of B12 deficiency depends on the underlying etiology. Reversible causes, such as metformin use > 4 months, PPI use > 12 months, and dietary deficiency, require treatment until appropriate levels are reached and symptoms are resolved.^4,11 The need for chronic metformin and PPI use should also be reassessed regularly. In patients who require long-term metformin use, IM administration of B12 1000 mcg annually should be considered, which will ensure adequate storage for more than 1 year.^12,13 In patients who require long-term PPI use, the risk and benefits of continued use should be measured, and if needed, the lowest possible effective PPI dose is recommended.¹⁴ Irreversible causes of B12 deficiency, such as advanced age, prior gastrectomy, chronic pancreatitis, or autoimmune pernicious anemia, require lifelong supplementation of B12.^4,11

In general, oral vitamin B12 replacement at 1000 to 2000 mcg daily may be as effective as parenteral replacement in patients with mild to moderate deficiency or neurologic symptoms.¹¹ On the other hand, patients with SCD often require parenteral replacement of B12 due to the severity of their deficiency or neurologic symptoms, need for more rapid improvement in symptoms, and prevention of irreversible neurological deficits. ^4,11 Appropriate B12 replacement in SCD requires intensive initial therapy which may involve IM B12 1000 mcg every other day for 2 weeks and additional IM supplementation every 2 to 3 months afterward until resolution of deficiency.^4,14 IM replacement may also be considered in patients who are nonadherent to oral replacement or have an underlying gastrointestinal condition that impairs enteral absorption.^4,11

B12 deficiency is frequently undertreated and can lead to progression of disease with significant morbidity. The need for highintensity dosing of B12 replacement is crucial in patients with SCD. Failure to respond to treatment, as shown from the lack of improvement of serum markers or symptoms, likely suggests undertreatment, treatment nonadherence, iron deficiency anemia, an unidentified malabsorption syndrome, or other diagnoses. In our case, significant undertreatment, compounded by his suspected iron deficiency anemia secondary to his polycythemia vera and chronic phlebotomies, are the most likel etiologies for his lack of clinical improvement.

Multiple factors may affect the prognosis of SCD. Males aged < 50 years with absence of anemia, spinal cord atrophy, Romberg sign, Babinski sign, or sensory deficits on examination have increased likelihood of eventual recovery of signs and symptoms of SCD; those with less spinal cord involvement (< 7 cord segments), contrast enhancement, and spinal cord edema also have improved outcomes.^4,15

Conclusion

SCD is a rare but serious complication of chronic vitamin B12 deficiency that presents with a variety of neurological findings and may be easily confused with other illnesses. The condition is easily overlooked or misdiagnosed; thus, it is crucial to differentiate B12 deficiency from other common causes of neurologic symptoms. Specific findings on MRI are useful to support the clinical diagnosis of SCD and guide clinical decisions. Given the prevalence of B12 deficiency in the older adult population, clinicians should remain alert to the possibility of these conditions in patients who present with progressive neuropathy. Once a patient is diagnosed with SCD secondary to a B12 deficiency, appropriate B12 replacement is critical. Appropriate B12 replacement is aggressive and involves IM B12 1000 mcg every other day for 2 to 3 weeks, followed by additional IM administration every 2 months before transitioning to oral therapy. As seen in this case, failure to adequately replenish B12 can lead to progression or lack of resolution of SCD symptoms.

Subacute combined degeneration (SCD) is an acquired neurologic complication of vitamin B12 (cobalamin) or, rarely, vitamin B9 (folate) deficiency. SCD is characterized by progressive demyelination of the dorsal and lateral spinal cord, resulting in peripheral neuropathy; gait ataxia; impaired proprioception, vibration, and fine touch; optic neuropathy; and cognitive impairment.¹ In addition to SCD, other neurologic manifestations of B12 deficiency include dementia, depression, visual symptoms due to optic atrophy, and behavioral changes.² The prevalence of SCD in the US has not been well documented, but B12 deficiency is reported at 6% in those aged < 60 years and 20% in those > 60 years^.3

Causes of B12 and B9 deficiency include advanced age, low nutritional intake (eg, vegan diet), impaired absorption (eg, inflammatory bowel disease, autoimmune pernicious anemia, gastrectomy, pancreatic disease), alcohol use, tapeworm infection, medications, and high metabolic states.^2,4 Impaired B12 absorption is common in patients taking medications, such as metformin and proton pump inhibitors (PPI), due to suppression of ileal membrane transport and intrinsic factor activity.^5-7 B-vitamin deficiency can be exacerbated by states of increased cellular turnover, such as polycythemia vera, due to elevated DNA synthesis.

Patients may experience permanent neurologic damage when the diagnosis and treatment of SCD are missed or delayed. Early diagnosis of SCD can be challenging due to lack of specific hematologic markers. In addition, many other conditions such as diabetic neuropathy, malnutrition, toxic neuropathy, sarcoidosis, HIV, multiple sclerosis, polycythemia vera, and iron deficiency anemia have similar presentations and clinical findings.⁸ Anemia and/or macrocytosis are not specific to B12 deficiency.⁴ In addition, patients with B12 deficiency may have a normal complete blood count (CBC); those with concomitant iron deficiency may have minimal or no mean corpuscular volume (MCV) elevation.⁴ In patients suspected to have B12 deficiency based on clinical presentation or laboratory findings of macrocytosis, serum methylmalonic acid (MMA) can serve as a direct measure of B12 activity, with levels > 0.75 μmol/L almost always indicating cobalamin deficiency. ⁹ On the other hand, plasma total homocysteine (tHcy) is a sensitive marker for B12 deficiency. The active form of B12, holotranscobalamin, has also emerged as a specific measure of B12 deficiency.⁹ However, in patients with SCD, measurement of these markers may be unnecessary due to the severity of their clinical symptoms. 

The diagnosis of SCD is further complicated because not all individuals who develop B12 or B9 deficiency will develop SCD. It is difficult to determine which patients will develop SCD because the minimum level of serum B12 required for normal function is unknown, and recent studies indicate that SCD may occur even at low-normal B12 and B9 levels.^2,4,10 Commonly, a serum B12 level of < 200 pg/mL is considered deficient, while a level between 200 and 300 pg/mL is considered borderline.⁴ The goal level of serum B12 is > 300 pg/mL, which is considered normal.⁴ While serologic findings of B-vitamin deficiency are only moderately specific, radiographic findings are highly sensitive and specific for SCD. According to Briani and colleagues, the most consistent finding in SCD on magnetic resonance imaging (MRI) is a “symmetrical, abnormally increased T2 signal intensity, commonly confined to posterior or posterior and lateral columns in the cervical and thoracic spinal cord.”²

We present a case of SCD in a patient with low-normal vitamin B12 levels who presented with progressive sensorimotor deficits and vision loss. The patient was subsequently diagnosed with SCD by radiologic workup. His course was complicated by worsening neurologic deficits despite B12 replacement. The progression of his clinical symptoms demonstrates the need for prompt, aggressive B12 replacement in patients diagnosed with SCD.

Case Presentation

A 63-year-old man presented for neurologic evaluation of progressive gait disturbance, paresthesia, blurred vision, and increasing falls despite use of a walker. Pertinent medical history included polycythemia vera requiring phlebotomy for approximately 9 years, alcohol use disorder (18 servings weekly), type 2 diabetes mellitus, and a remote episode of transient ischemic attack (TIA). The patient reported a 5-year history of burning pain in all extremities. A prior physician diagnosis attributed the symptoms to polyneuropathy secondary to iron deficiency anemia in the setting of chronic phlebotomy for polycythemia vera and high erythrogenesis. He was prescribed gabapentin 600 mg 3 times daily for pain control. B12 deficiency was considered an unlikely etiology due to a low-normal serum level of 305 pg/mL (reference range, 190-950 pg/mL) and normocytosis, with MCV of 88 fL (reference range, 80-100 fL). The patient also reported a 3-year history of blurred vision, which was initially attributed to be secondary to diabetic retinopathy. One week prior to presenting to our clinic, he was evaluated by ophthalmology for new-onset, bilateral central visual field defects, and he was diagnosed with nutritional optic neuropathy.

Previous cardiac evaluation failed to provide a diagnosis for syncopal episodes. MRI of the brain revealed nonspecific white matter changes consistent with chronic microvascular ischemic disease. Electromyography was limited due to pain but showed severe peripheral neuropathy. Laboratory results showed megalocytosis, low-normal serum B12 levels, and low serum folate levels (Table 2). The patient was diagnosed with polyneuropathy and was given intramuscular (IM) vitamin B12 1000 mcg once and a daily multivitamin (containing 25 mcg of B12). He was counseled on alcohol abstinence and medication adherence and was scheduled for follow-up in 3 months. He continued outpatient phlebotomy every 6 weeks for polycythemia.

At 3-month follow-up, the patient reported medication adherence, continued alcohol use, and worsening of symptoms. Falls, which now occurred 2 to 3 times weekly despite proper use of a walker, were described as sudden loss of bilateral lower extremity strength without loss of consciousness, palpitations, or other prodrome. Laboratory results showed minimal changes. Physical examination of the patient demonstrated similar deficits as on initial presentation. The patient received one additional B12 1000 mcg IM. Gabapentin was replaced with pregabalin 75 mg twice daily due to persistent uncontrolled pain and paresthesia. The patient was scheduled for a 3-month followup (6 months from initial visit) and repeat serology.

At 6-month follow-up, the patient showed continued progression of disease with significant difficulty using the walker, worsening falls, and wheelchair use required. Physical examination showed decreased sensation bilaterally up to the knees, absent bilateral patellar and Achilles reflexes, and unsteady gait. Laboratory results showed persistent subclinical B12 deficiency. MRI of the brain and spine showed high T2 signaling in a pattern highly specific for SCD. A formal diagnosis of SCD was made. The patient received an additional B12 1000 mcg IM once. Follow-up phone call with the patient 1 month later revealed no progression or improvement of symptoms.

Radiographic Findings

MRI of the cervical and thoracic spine demonstrated abnormal high T2 signal starting from C2 and extending along the course of the cervical and thoracic spinal cord (Figure). MRI in SCD classically shows symmetric, bilateral high T2 signal within the dorsal columns; on axial images, there is typically an inverted “V” sign.^2,4 There can also be abnormal cerebral white matter change; however, MRI of the brain in this patient did not show any abnormalities.2 The imaging differential for this appearance includes other metabolic deficiencies/toxicities: copper deficiency; vitamin E deficiency; methotrexateinduced myelopathy, and infectious causes: HIV vacuolar myelopathy; and neurosyphilis (tabes dorsalis).⁴

Discussion

This case demonstrates the clinical and radiographic findings of SCD and underscores the need for high-intensity dosing of B12 replacement in patients with SCD to prevent progression of the disease and development of morbidities.

Symptoms of SCD may manifest even when the vitamin levels are in low-normal levels. Its presentation is often nonspecific, thus radiologic workup is beneficial to elucidate the clinical picture. We support the use of spinal MRI in patients with clinical suspicion of SCD to help rule out other causes of myelopathy. However, an MRI is not indicated in all patients with B12 deficiency, especially those without myelopathic symptoms. Additionally, follow-up spinal MRIs are useful in monitoring the progression or improvement of SCD after B12 replacement.² It is important to note that the MRI findings in SCD are not specific to B12 deficiency; other causes may present with similar radiographic findings.⁴ Therefore, radiologic findings must be correlated with a patient’s clinical presentation.

B12 replacement improves and may resolve clinical symptoms and abnormal radiographic findings of SCD. The treatment duration of B12 deficiency depends on the underlying etiology. Reversible causes, such as metformin use > 4 months, PPI use > 12 months, and dietary deficiency, require treatment until appropriate levels are reached and symptoms are resolved.^4,11 The need for chronic metformin and PPI use should also be reassessed regularly. In patients who require long-term metformin use, IM administration of B12 1000 mcg annually should be considered, which will ensure adequate storage for more than 1 year.^12,13 In patients who require long-term PPI use, the risk and benefits of continued use should be measured, and if needed, the lowest possible effective PPI dose is recommended.¹⁴ Irreversible causes of B12 deficiency, such as advanced age, prior gastrectomy, chronic pancreatitis, or autoimmune pernicious anemia, require lifelong supplementation of B12.^4,11

In general, oral vitamin B12 replacement at 1000 to 2000 mcg daily may be as effective as parenteral replacement in patients with mild to moderate deficiency or neurologic symptoms.¹¹ On the other hand, patients with SCD often require parenteral replacement of B12 due to the severity of their deficiency or neurologic symptoms, need for more rapid improvement in symptoms, and prevention of irreversible neurological deficits. ^4,11 Appropriate B12 replacement in SCD requires intensive initial therapy which may involve IM B12 1000 mcg every other day for 2 weeks and additional IM supplementation every 2 to 3 months afterward until resolution of deficiency.^4,14 IM replacement may also be considered in patients who are nonadherent to oral replacement or have an underlying gastrointestinal condition that impairs enteral absorption.^4,11

B12 deficiency is frequently undertreated and can lead to progression of disease with significant morbidity. The need for highintensity dosing of B12 replacement is crucial in patients with SCD. Failure to respond to treatment, as shown from the lack of improvement of serum markers or symptoms, likely suggests undertreatment, treatment nonadherence, iron deficiency anemia, an unidentified malabsorption syndrome, or other diagnoses. In our case, significant undertreatment, compounded by his suspected iron deficiency anemia secondary to his polycythemia vera and chronic phlebotomies, are the most likel etiologies for his lack of clinical improvement.

Multiple factors may affect the prognosis of SCD. Males aged < 50 years with absence of anemia, spinal cord atrophy, Romberg sign, Babinski sign, or sensory deficits on examination have increased likelihood of eventual recovery of signs and symptoms of SCD; those with less spinal cord involvement (< 7 cord segments), contrast enhancement, and spinal cord edema also have improved outcomes.^4,15

Conclusion

SCD is a rare but serious complication of chronic vitamin B12 deficiency that presents with a variety of neurological findings and may be easily confused with other illnesses. The condition is easily overlooked or misdiagnosed; thus, it is crucial to differentiate B12 deficiency from other common causes of neurologic symptoms. Specific findings on MRI are useful to support the clinical diagnosis of SCD and guide clinical decisions. Given the prevalence of B12 deficiency in the older adult population, clinicians should remain alert to the possibility of these conditions in patients who present with progressive neuropathy. Once a patient is diagnosed with SCD secondary to a B12 deficiency, appropriate B12 replacement is critical. Appropriate B12 replacement is aggressive and involves IM B12 1000 mcg every other day for 2 to 3 weeks, followed by additional IM administration every 2 months before transitioning to oral therapy. As seen in this case, failure to adequately replenish B12 can lead to progression or lack of resolution of SCD symptoms.

Hemiballismus is an acquired hyperkinetic movement disorder characterized by unilateral, involuntary, often large-amplitude limb movements. Ballistic movements are now considered to be on the choreiform spectrum.1 Movements usually involve both the arm and leg, and in half of cases, facial movements such as tongue clucking and grimacing are seen.^2,3 Presentations of hemiballismus vary in severity from intermittent to nearly continuous movements, which, in some cases, may lead to exhaustion, injury, or disability. Some patients are unable to ambulate or feed themselves with the affected limb.

Background

The 2 most common causes of hemichorea-hemiballismus are stroke and hyperglycemia, with an incidence of 4% and unknown incidence, respectively.^1,3,4 Other causes include HIV, traumatic brain injury, encephalitis, vasculitis, mass effect, multiple sclerosis, and adverse drug reactions. ^4-7 Acute or subacute hemiballismus is classically attributed to a lesion in subthalamic nucleus (STN), but this is true only in a minority of cases. Hemiballismus can be caused by any abnormality in various subnuclei of the basal ganglia, including the classic location in the STN, striatum, and globus pallidus.⁴ Evidence shows the lesions typically involve a functional network connected to the posterolateral putamen.⁸

Although not commonly recognized, hyperglycemia in patients with type 2 diabetes mellitus (T2DM) is the second most common cause of hemichoreahemiballismus. ³ Over the past 90 years, numerous case reports have described patients with DM with acute and subacute onset of hemiballistic and hemichoreiform movements while in a hyperglycemic state or after its resolution. Reported cases have been limited to small numbers of patients with only a few larger-scale reviews of more than 20 patients.^7,9 Most reported cases involve geriatric patients and more commonly, females of Eastern Asian descent with an average age of onset of 71 years.^4,10 Patients typically present with glucose levels from 500 to 1,000 mg/dL and hemoglobin A1c (HbA1c) levels almost double the normal values. Interestingly, neuroimaging findings in these patients have consistently shown hyperintense signal in the contralateral basal ganglia on T1-weighted magnetic resonance images (MRIs). Noncontrast computed tomography (CT) shows well-defined unilateral increased density in the contralateral basal ganglia without mass effect.^1,9,11

This report aims to illustrate and enhance the understanding of hemiballismus associated with hyperglycemia. One patient presented to the US Department of Veterans Affairs (VA) Bay Pines VA Healthcare System (BPVAHCS) in Florida, which motivated us to search for other similar cases. We reviewed the charts of 2 other patients who presented to BPVAHCS over the past 10 years. The first case presented with severe hyperglycemia and abnormal movements that were not clearly diagnosed as hemiballismus. MRI findings were characteristic and assisted in making the diagnosis. The second case was misdiagnosed as hemiballismus secondary to ischemic stroke. The third case was initially diagnosed as conversion disorder until movements worsened and the correct diagnosis of hyperglycemia-induced hemichorea hemiballismus was confirmed by the pathognomonic neuroimaging findings.

Case Presentations

Case 1

A 65-year-old male with a history of uncontrolled T2DM presented with repetitive twitching and kicking movements that involved his left upper and lower extremities for 3 weeks. The patient reported that he did not take his medications or follow the recommended diabetes diet. His HbA1c on admission was 12.2% with a serum glucose of 254 mg/dL. The MRI showed a hyperintense T1 signal within the right basal ganglia including the right caudate with sparing of the internal capsule (Figure 1). There was no associated mass effect or restricted diffusion. It was compatible with a diagnosis of hyperglycemia- induced hemichorea-hemiballismus. The patient was advised to resume taking glipizide 10 mg daily, metformin 1,000 mg by mouth twice daily, and to begin 10 units of 70/30 insulin aspart 15 minutes before meals twice daily, and to follow a low carbohydrate diet, with reduce dietary intake of sugar. At his 1-month follow-up visit, the patient reported an improvement in his involuntary movements. At the 5-month follow-up, the patient’s HbA1c level was 10.4% and his hyperkinetic movements had completely resolved.

Case 2

of T2DM, hypertension, and hyperlipidemia was admitted due to increased jerky movements in the left upper extremity. On admission, his vital signs were within normal limits and his physical examination demonstrated choreoathetoid movements with ballistic components of his left upper extremity. His laboratory results showed a glucose level of 528 mg/dL with a HbA1c of 16.3%. An initial CT obtained in the emergency department (ED) demonstrated a well-defined hyperdensity in the striatal (caudate and lentiform nucleus) region (Figure 2). There was no associated edema/mass effect that would be typical for an intracranial hemorrhage.

An MRI obtained 1 week later showed hyperintense TI signal corresponding to the basal ganglia (Figure 3). In addition, there was a questionable lacunar infarct in the right internal capsule. Due to lack of awareness regarding hyperglycemic associated basal ganglia changes, the patient’s movement disorder was presumed to be ischemic in etiology. The patient was prescribed oral amantadine 100 mg 3 times daily for the hemiballismus in conjunction with treatment of his T2DM. The only follow-up occurred 5 weeks later, which showed no improvement of uncontrollable movements. Imaging at that time (not available) indicated the persistence of the abnormal signal in the right basal ganglia. This patient died later that year without further follow-up.

Case 3

A 78-year-old white male with a history of syncope, transient ischemic attacks (TIAs), and poorly controlled T2DM presented with a 1-month history of progressively worsening involuntary, left-sided movements that began in his left shoulder and advanced to involve his arm, hand, and leg, and the left side of his face with grimacing and clucking of his tongue. Three weeks earlier, the patient had been discharged from the ED with a diagnosis of conversion disorder particularly because he experienced decreased movements when given a dose of Vitamin D. It was overlooked that administration of haloperidol had occurred a few hours before, and because the sounds made by his tongue were not felt to be consistent with a known movement disorder. A MRI of the brain was read as normal.

The patient returned 3 weeks later (the original presentation) due to his inability to perform activities of daily living because of his worsening involuntary movements. On admission, his HbA1c was 11.1% and his glucose was 167 mg/dL. On chart review, it was revealed that the patient’s HbA1c had been > 9% for the past 3 years with an increase from 10.1% to 11.1% in the 3 months preceding the onset of his symptoms.

On admission a MRI showed a unilateral right-sided T1 hyperintensity in the basal ganglia, no acute ischemia (Figure 4). In retrospect, subtle increased T1 signal can be seen on the earlier MRI (Figure 5). In view of the patient’s left-sided symptoms, DM, and MRI findings, a diagnosis of hyperglycemia-induced hemichorea- hemiballismus was made as the etiology of the patient’s symptoms.

The patient was prescribed numerous medications to control his hyperkinesia including (and in combination): benztropine, gabapentin, baclofen, diphenhydramine, benzodiazepines, risperidone, olanzapine, and valproic acid, which did not control his movements. Ultimately, his hyperglycemic hemiballismus improved with tight glycemic control and oral tetrabenazine 12.5 mg twice daily. This patient underwent a protracted course of treatment with 17 days of inpatient medical admission, 3 weeks inpatient rehabilitation, and subsequent transfer to an assisted living facility.

Discussion

The 3 cases presented in this report contribute to the evidence that severe persistent hyperglycemia can result in movement disorders that mimic those seen after basal ganglia strokes. As with Case 2, past literature describes many cases of acute hyperglycemic episodes with glucose ranging from 500 to 1,000 mg/mL presenting with hemiballismus.^1,3 However, there are many cases that describe hemiballismus occurring after glycemic correction, persisting despite glycemic correction, and presenting without an acute hyperglycemic episode, but in the setting of elevated HbA_1c, as in Case 3.^12,13 Notably, all 3 cases in this series had marked elevation in their HbA_1c levels, which suggests that a more chronic hyperglycemic state or multiple shorter periods of hyperglycemia may be necessary to produce the described hyperkinetic movements.

Case reports describe the pathognomonic T1 hyperintensity of the basal ganglia that is identified in all 3 cases presented here. While the exact etiology remains unclear, the to metabolic derangements caused by hyperviscosity of the blood in the small end arteries feeding the basal ganglia.^3,11 These abnormalities in turn interrupt the signaling cascade with abnormal firing rates or firing patterns, leading to reduced inhibition of the motor thalamus and ultimately present as hemiballismus.^1,3,7 While most cases presented with unilateral hyperkinesis and associated contralateral basal ganglia abnormalities, there are reports of both unilateral and bilateral movements associated with bilateral basal ganglia hyperintensities on imaging. ⁹ The predilection for unilateral brain lesions may be explained by the varying degree of small vessel disease in different areas of the brain leading to perfusion deficits worsened by hyper viscosity. Further research into this is required to elucidate the exact pathophysiologic mechanism.

The course of disease for patients ranges from resolution within hours of tight glycemic control to persistent movements for > 3 months with a gradual improvement in severity.^12,13 Treatments center on the importance of tight glycemic control to protect against the protracted course described in Case 3. Swift recognition of this rare condition is critical because improved glycemic control decreases the severity and duration of this disease. The significant disability associated with Case 3 highlights the need for prompt recognition and early, aggressive glycemic management to prevent the progression of hemiballismus. In addition to glycemic control, various CNS medications such as typical and atypical antipsychotics and tetrabenazine are firstline therapy with chemodenervation and surgical lesioning in cases unresponsive to medication therapy.

When unrecognized, hyperglycemic hemiballismus is associated with significant morbidity and mortality. The patients presented in this report were subject to either delayed diagnosis or misdiagnosis as stroke or psychiatric disorder. The rarity of the disorder, lack of evidence delineating pathogenesis and causality, low level of awareness, and varying presentations of patients all contribute to the challenge of recognizing, diagnosing, and treating hemiballismus due to hyperglycemia. This challenge can subsequently result in deteriorating symptoms, prolonged hospital stays, and unnecessary health care costs.

Conclusion

While hemiballismus due to severe persistent hyperglycemia is rare, the goal of this report is to highlight its occurrence in patients with T2DM. Further research can help develop a standardized, effective treatment strategy for these patients. Currently, lowering and maintaining appropriate glucose and HbA_1c levels is the most effective treatment approach. Potential areas of research include alternative medical and surgical treatment interventions for patients while glycemic control is being achieved or for those who fail to benefit from glycemic control alone. Some success has been demonstrated with the use of antidopaminergic medications such as atypical antipsychotics and tetrabenazine and these medications should be considered when tight, sustained glycemic control alone is not successful in treating this disorder in the acute stages. Hopefully, with increasing awareness and recognition of hemiballismus related to hyperglycemia, more large-scale clinical trials can be conducted that will result in an effective treatment strategy for this devastating disorder.

Hemiballismus is an acquired hyperkinetic movement disorder characterized by unilateral, involuntary, often large-amplitude limb movements. Ballistic movements are now considered to be on the choreiform spectrum.1 Movements usually involve both the arm and leg, and in half of cases, facial movements such as tongue clucking and grimacing are seen.^2,3 Presentations of hemiballismus vary in severity from intermittent to nearly continuous movements, which, in some cases, may lead to exhaustion, injury, or disability. Some patients are unable to ambulate or feed themselves with the affected limb.

Background

The 2 most common causes of hemichorea-hemiballismus are stroke and hyperglycemia, with an incidence of 4% and unknown incidence, respectively.^1,3,4 Other causes include HIV, traumatic brain injury, encephalitis, vasculitis, mass effect, multiple sclerosis, and adverse drug reactions. ^4-7 Acute or subacute hemiballismus is classically attributed to a lesion in subthalamic nucleus (STN), but this is true only in a minority of cases. Hemiballismus can be caused by any abnormality in various subnuclei of the basal ganglia, including the classic location in the STN, striatum, and globus pallidus.⁴ Evidence shows the lesions typically involve a functional network connected to the posterolateral putamen.⁸

Although not commonly recognized, hyperglycemia in patients with type 2 diabetes mellitus (T2DM) is the second most common cause of hemichoreahemiballismus. ³ Over the past 90 years, numerous case reports have described patients with DM with acute and subacute onset of hemiballistic and hemichoreiform movements while in a hyperglycemic state or after its resolution. Reported cases have been limited to small numbers of patients with only a few larger-scale reviews of more than 20 patients.^7,9 Most reported cases involve geriatric patients and more commonly, females of Eastern Asian descent with an average age of onset of 71 years.^4,10 Patients typically present with glucose levels from 500 to 1,000 mg/dL and hemoglobin A1c (HbA1c) levels almost double the normal values. Interestingly, neuroimaging findings in these patients have consistently shown hyperintense signal in the contralateral basal ganglia on T1-weighted magnetic resonance images (MRIs). Noncontrast computed tomography (CT) shows well-defined unilateral increased density in the contralateral basal ganglia without mass effect.^1,9,11

This report aims to illustrate and enhance the understanding of hemiballismus associated with hyperglycemia. One patient presented to the US Department of Veterans Affairs (VA) Bay Pines VA Healthcare System (BPVAHCS) in Florida, which motivated us to search for other similar cases. We reviewed the charts of 2 other patients who presented to BPVAHCS over the past 10 years. The first case presented with severe hyperglycemia and abnormal movements that were not clearly diagnosed as hemiballismus. MRI findings were characteristic and assisted in making the diagnosis. The second case was misdiagnosed as hemiballismus secondary to ischemic stroke. The third case was initially diagnosed as conversion disorder until movements worsened and the correct diagnosis of hyperglycemia-induced hemichorea hemiballismus was confirmed by the pathognomonic neuroimaging findings.

Case Presentations

Case 1

A 65-year-old male with a history of uncontrolled T2DM presented with repetitive twitching and kicking movements that involved his left upper and lower extremities for 3 weeks. The patient reported that he did not take his medications or follow the recommended diabetes diet. His HbA1c on admission was 12.2% with a serum glucose of 254 mg/dL. The MRI showed a hyperintense T1 signal within the right basal ganglia including the right caudate with sparing of the internal capsule (Figure 1). There was no associated mass effect or restricted diffusion. It was compatible with a diagnosis of hyperglycemia- induced hemichorea-hemiballismus. The patient was advised to resume taking glipizide 10 mg daily, metformin 1,000 mg by mouth twice daily, and to begin 10 units of 70/30 insulin aspart 15 minutes before meals twice daily, and to follow a low carbohydrate diet, with reduce dietary intake of sugar. At his 1-month follow-up visit, the patient reported an improvement in his involuntary movements. At the 5-month follow-up, the patient’s HbA1c level was 10.4% and his hyperkinetic movements had completely resolved.

Case 2

of T2DM, hypertension, and hyperlipidemia was admitted due to increased jerky movements in the left upper extremity. On admission, his vital signs were within normal limits and his physical examination demonstrated choreoathetoid movements with ballistic components of his left upper extremity. His laboratory results showed a glucose level of 528 mg/dL with a HbA1c of 16.3%. An initial CT obtained in the emergency department (ED) demonstrated a well-defined hyperdensity in the striatal (caudate and lentiform nucleus) region (Figure 2). There was no associated edema/mass effect that would be typical for an intracranial hemorrhage.

An MRI obtained 1 week later showed hyperintense TI signal corresponding to the basal ganglia (Figure 3). In addition, there was a questionable lacunar infarct in the right internal capsule. Due to lack of awareness regarding hyperglycemic associated basal ganglia changes, the patient’s movement disorder was presumed to be ischemic in etiology. The patient was prescribed oral amantadine 100 mg 3 times daily for the hemiballismus in conjunction with treatment of his T2DM. The only follow-up occurred 5 weeks later, which showed no improvement of uncontrollable movements. Imaging at that time (not available) indicated the persistence of the abnormal signal in the right basal ganglia. This patient died later that year without further follow-up.

Case 3

A 78-year-old white male with a history of syncope, transient ischemic attacks (TIAs), and poorly controlled T2DM presented with a 1-month history of progressively worsening involuntary, left-sided movements that began in his left shoulder and advanced to involve his arm, hand, and leg, and the left side of his face with grimacing and clucking of his tongue. Three weeks earlier, the patient had been discharged from the ED with a diagnosis of conversion disorder particularly because he experienced decreased movements when given a dose of Vitamin D. It was overlooked that administration of haloperidol had occurred a few hours before, and because the sounds made by his tongue were not felt to be consistent with a known movement disorder. A MRI of the brain was read as normal.

The patient returned 3 weeks later (the original presentation) due to his inability to perform activities of daily living because of his worsening involuntary movements. On admission, his HbA1c was 11.1% and his glucose was 167 mg/dL. On chart review, it was revealed that the patient’s HbA1c had been > 9% for the past 3 years with an increase from 10.1% to 11.1% in the 3 months preceding the onset of his symptoms.

On admission a MRI showed a unilateral right-sided T1 hyperintensity in the basal ganglia, no acute ischemia (Figure 4). In retrospect, subtle increased T1 signal can be seen on the earlier MRI (Figure 5). In view of the patient’s left-sided symptoms, DM, and MRI findings, a diagnosis of hyperglycemia-induced hemichorea- hemiballismus was made as the etiology of the patient’s symptoms.

The patient was prescribed numerous medications to control his hyperkinesia including (and in combination): benztropine, gabapentin, baclofen, diphenhydramine, benzodiazepines, risperidone, olanzapine, and valproic acid, which did not control his movements. Ultimately, his hyperglycemic hemiballismus improved with tight glycemic control and oral tetrabenazine 12.5 mg twice daily. This patient underwent a protracted course of treatment with 17 days of inpatient medical admission, 3 weeks inpatient rehabilitation, and subsequent transfer to an assisted living facility.

Discussion

The 3 cases presented in this report contribute to the evidence that severe persistent hyperglycemia can result in movement disorders that mimic those seen after basal ganglia strokes. As with Case 2, past literature describes many cases of acute hyperglycemic episodes with glucose ranging from 500 to 1,000 mg/mL presenting with hemiballismus.^1,3 However, there are many cases that describe hemiballismus occurring after glycemic correction, persisting despite glycemic correction, and presenting without an acute hyperglycemic episode, but in the setting of elevated HbA_1c, as in Case 3.^12,13 Notably, all 3 cases in this series had marked elevation in their HbA_1c levels, which suggests that a more chronic hyperglycemic state or multiple shorter periods of hyperglycemia may be necessary to produce the described hyperkinetic movements.

Case reports describe the pathognomonic T1 hyperintensity of the basal ganglia that is identified in all 3 cases presented here. While the exact etiology remains unclear, the to metabolic derangements caused by hyperviscosity of the blood in the small end arteries feeding the basal ganglia.^3,11 These abnormalities in turn interrupt the signaling cascade with abnormal firing rates or firing patterns, leading to reduced inhibition of the motor thalamus and ultimately present as hemiballismus.^1,3,7 While most cases presented with unilateral hyperkinesis and associated contralateral basal ganglia abnormalities, there are reports of both unilateral and bilateral movements associated with bilateral basal ganglia hyperintensities on imaging. ⁹ The predilection for unilateral brain lesions may be explained by the varying degree of small vessel disease in different areas of the brain leading to perfusion deficits worsened by hyper viscosity. Further research into this is required to elucidate the exact pathophysiologic mechanism.

The course of disease for patients ranges from resolution within hours of tight glycemic control to persistent movements for > 3 months with a gradual improvement in severity.^12,13 Treatments center on the importance of tight glycemic control to protect against the protracted course described in Case 3. Swift recognition of this rare condition is critical because improved glycemic control decreases the severity and duration of this disease. The significant disability associated with Case 3 highlights the need for prompt recognition and early, aggressive glycemic management to prevent the progression of hemiballismus. In addition to glycemic control, various CNS medications such as typical and atypical antipsychotics and tetrabenazine are firstline therapy with chemodenervation and surgical lesioning in cases unresponsive to medication therapy.

When unrecognized, hyperglycemic hemiballismus is associated with significant morbidity and mortality. The patients presented in this report were subject to either delayed diagnosis or misdiagnosis as stroke or psychiatric disorder. The rarity of the disorder, lack of evidence delineating pathogenesis and causality, low level of awareness, and varying presentations of patients all contribute to the challenge of recognizing, diagnosing, and treating hemiballismus due to hyperglycemia. This challenge can subsequently result in deteriorating symptoms, prolonged hospital stays, and unnecessary health care costs.

Conclusion

While hemiballismus due to severe persistent hyperglycemia is rare, the goal of this report is to highlight its occurrence in patients with T2DM. Further research can help develop a standardized, effective treatment strategy for these patients. Currently, lowering and maintaining appropriate glucose and HbA_1c levels is the most effective treatment approach. Potential areas of research include alternative medical and surgical treatment interventions for patients while glycemic control is being achieved or for those who fail to benefit from glycemic control alone. Some success has been demonstrated with the use of antidopaminergic medications such as atypical antipsychotics and tetrabenazine and these medications should be considered when tight, sustained glycemic control alone is not successful in treating this disorder in the acute stages. Hopefully, with increasing awareness and recognition of hemiballismus related to hyperglycemia, more large-scale clinical trials can be conducted that will result in an effective treatment strategy for this devastating disorder.

Hemiballismus is an acquired hyperkinetic movement disorder characterized by unilateral, involuntary, often large-amplitude limb movements. Ballistic movements are now considered to be on the choreiform spectrum.1 Movements usually involve both the arm and leg, and in half of cases, facial movements such as tongue clucking and grimacing are seen.^2,3 Presentations of hemiballismus vary in severity from intermittent to nearly continuous movements, which, in some cases, may lead to exhaustion, injury, or disability. Some patients are unable to ambulate or feed themselves with the affected limb.

Background

The 2 most common causes of hemichorea-hemiballismus are stroke and hyperglycemia, with an incidence of 4% and unknown incidence, respectively.^1,3,4 Other causes include HIV, traumatic brain injury, encephalitis, vasculitis, mass effect, multiple sclerosis, and adverse drug reactions. ^4-7 Acute or subacute hemiballismus is classically attributed to a lesion in subthalamic nucleus (STN), but this is true only in a minority of cases. Hemiballismus can be caused by any abnormality in various subnuclei of the basal ganglia, including the classic location in the STN, striatum, and globus pallidus.⁴ Evidence shows the lesions typically involve a functional network connected to the posterolateral putamen.⁸

Although not commonly recognized, hyperglycemia in patients with type 2 diabetes mellitus (T2DM) is the second most common cause of hemichoreahemiballismus. ³ Over the past 90 years, numerous case reports have described patients with DM with acute and subacute onset of hemiballistic and hemichoreiform movements while in a hyperglycemic state or after its resolution. Reported cases have been limited to small numbers of patients with only a few larger-scale reviews of more than 20 patients.^7,9 Most reported cases involve geriatric patients and more commonly, females of Eastern Asian descent with an average age of onset of 71 years.^4,10 Patients typically present with glucose levels from 500 to 1,000 mg/dL and hemoglobin A1c (HbA1c) levels almost double the normal values. Interestingly, neuroimaging findings in these patients have consistently shown hyperintense signal in the contralateral basal ganglia on T1-weighted magnetic resonance images (MRIs). Noncontrast computed tomography (CT) shows well-defined unilateral increased density in the contralateral basal ganglia without mass effect.^1,9,11

This report aims to illustrate and enhance the understanding of hemiballismus associated with hyperglycemia. One patient presented to the US Department of Veterans Affairs (VA) Bay Pines VA Healthcare System (BPVAHCS) in Florida, which motivated us to search for other similar cases. We reviewed the charts of 2 other patients who presented to BPVAHCS over the past 10 years. The first case presented with severe hyperglycemia and abnormal movements that were not clearly diagnosed as hemiballismus. MRI findings were characteristic and assisted in making the diagnosis. The second case was misdiagnosed as hemiballismus secondary to ischemic stroke. The third case was initially diagnosed as conversion disorder until movements worsened and the correct diagnosis of hyperglycemia-induced hemichorea hemiballismus was confirmed by the pathognomonic neuroimaging findings.

Case Presentations

Case 1

A 65-year-old male with a history of uncontrolled T2DM presented with repetitive twitching and kicking movements that involved his left upper and lower extremities for 3 weeks. The patient reported that he did not take his medications or follow the recommended diabetes diet. His HbA1c on admission was 12.2% with a serum glucose of 254 mg/dL. The MRI showed a hyperintense T1 signal within the right basal ganglia including the right caudate with sparing of the internal capsule (Figure 1). There was no associated mass effect or restricted diffusion. It was compatible with a diagnosis of hyperglycemia- induced hemichorea-hemiballismus. The patient was advised to resume taking glipizide 10 mg daily, metformin 1,000 mg by mouth twice daily, and to begin 10 units of 70/30 insulin aspart 15 minutes before meals twice daily, and to follow a low carbohydrate diet, with reduce dietary intake of sugar. At his 1-month follow-up visit, the patient reported an improvement in his involuntary movements. At the 5-month follow-up, the patient’s HbA1c level was 10.4% and his hyperkinetic movements had completely resolved.

Case 2

of T2DM, hypertension, and hyperlipidemia was admitted due to increased jerky movements in the left upper extremity. On admission, his vital signs were within normal limits and his physical examination demonstrated choreoathetoid movements with ballistic components of his left upper extremity. His laboratory results showed a glucose level of 528 mg/dL with a HbA1c of 16.3%. An initial CT obtained in the emergency department (ED) demonstrated a well-defined hyperdensity in the striatal (caudate and lentiform nucleus) region (Figure 2). There was no associated edema/mass effect that would be typical for an intracranial hemorrhage.

An MRI obtained 1 week later showed hyperintense TI signal corresponding to the basal ganglia (Figure 3). In addition, there was a questionable lacunar infarct in the right internal capsule. Due to lack of awareness regarding hyperglycemic associated basal ganglia changes, the patient’s movement disorder was presumed to be ischemic in etiology. The patient was prescribed oral amantadine 100 mg 3 times daily for the hemiballismus in conjunction with treatment of his T2DM. The only follow-up occurred 5 weeks later, which showed no improvement of uncontrollable movements. Imaging at that time (not available) indicated the persistence of the abnormal signal in the right basal ganglia. This patient died later that year without further follow-up.

Case 3

A 78-year-old white male with a history of syncope, transient ischemic attacks (TIAs), and poorly controlled T2DM presented with a 1-month history of progressively worsening involuntary, left-sided movements that began in his left shoulder and advanced to involve his arm, hand, and leg, and the left side of his face with grimacing and clucking of his tongue. Three weeks earlier, the patient had been discharged from the ED with a diagnosis of conversion disorder particularly because he experienced decreased movements when given a dose of Vitamin D. It was overlooked that administration of haloperidol had occurred a few hours before, and because the sounds made by his tongue were not felt to be consistent with a known movement disorder. A MRI of the brain was read as normal.

The patient returned 3 weeks later (the original presentation) due to his inability to perform activities of daily living because of his worsening involuntary movements. On admission, his HbA1c was 11.1% and his glucose was 167 mg/dL. On chart review, it was revealed that the patient’s HbA1c had been > 9% for the past 3 years with an increase from 10.1% to 11.1% in the 3 months preceding the onset of his symptoms.

On admission a MRI showed a unilateral right-sided T1 hyperintensity in the basal ganglia, no acute ischemia (Figure 4). In retrospect, subtle increased T1 signal can be seen on the earlier MRI (Figure 5). In view of the patient’s left-sided symptoms, DM, and MRI findings, a diagnosis of hyperglycemia-induced hemichorea- hemiballismus was made as the etiology of the patient’s symptoms.

The patient was prescribed numerous medications to control his hyperkinesia including (and in combination): benztropine, gabapentin, baclofen, diphenhydramine, benzodiazepines, risperidone, olanzapine, and valproic acid, which did not control his movements. Ultimately, his hyperglycemic hemiballismus improved with tight glycemic control and oral tetrabenazine 12.5 mg twice daily. This patient underwent a protracted course of treatment with 17 days of inpatient medical admission, 3 weeks inpatient rehabilitation, and subsequent transfer to an assisted living facility.

Discussion

The 3 cases presented in this report contribute to the evidence that severe persistent hyperglycemia can result in movement disorders that mimic those seen after basal ganglia strokes. As with Case 2, past literature describes many cases of acute hyperglycemic episodes with glucose ranging from 500 to 1,000 mg/mL presenting with hemiballismus.^1,3 However, there are many cases that describe hemiballismus occurring after glycemic correction, persisting despite glycemic correction, and presenting without an acute hyperglycemic episode, but in the setting of elevated HbA_1c, as in Case 3.^12,13 Notably, all 3 cases in this series had marked elevation in their HbA_1c levels, which suggests that a more chronic hyperglycemic state or multiple shorter periods of hyperglycemia may be necessary to produce the described hyperkinetic movements.

Case reports describe the pathognomonic T1 hyperintensity of the basal ganglia that is identified in all 3 cases presented here. While the exact etiology remains unclear, the to metabolic derangements caused by hyperviscosity of the blood in the small end arteries feeding the basal ganglia.^3,11 These abnormalities in turn interrupt the signaling cascade with abnormal firing rates or firing patterns, leading to reduced inhibition of the motor thalamus and ultimately present as hemiballismus.^1,3,7 While most cases presented with unilateral hyperkinesis and associated contralateral basal ganglia abnormalities, there are reports of both unilateral and bilateral movements associated with bilateral basal ganglia hyperintensities on imaging. ⁹ The predilection for unilateral brain lesions may be explained by the varying degree of small vessel disease in different areas of the brain leading to perfusion deficits worsened by hyper viscosity. Further research into this is required to elucidate the exact pathophysiologic mechanism.

The course of disease for patients ranges from resolution within hours of tight glycemic control to persistent movements for > 3 months with a gradual improvement in severity.^12,13 Treatments center on the importance of tight glycemic control to protect against the protracted course described in Case 3. Swift recognition of this rare condition is critical because improved glycemic control decreases the severity and duration of this disease. The significant disability associated with Case 3 highlights the need for prompt recognition and early, aggressive glycemic management to prevent the progression of hemiballismus. In addition to glycemic control, various CNS medications such as typical and atypical antipsychotics and tetrabenazine are firstline therapy with chemodenervation and surgical lesioning in cases unresponsive to medication therapy.

When unrecognized, hyperglycemic hemiballismus is associated with significant morbidity and mortality. The patients presented in this report were subject to either delayed diagnosis or misdiagnosis as stroke or psychiatric disorder. The rarity of the disorder, lack of evidence delineating pathogenesis and causality, low level of awareness, and varying presentations of patients all contribute to the challenge of recognizing, diagnosing, and treating hemiballismus due to hyperglycemia. This challenge can subsequently result in deteriorating symptoms, prolonged hospital stays, and unnecessary health care costs.

Conclusion

While hemiballismus due to severe persistent hyperglycemia is rare, the goal of this report is to highlight its occurrence in patients with T2DM. Further research can help develop a standardized, effective treatment strategy for these patients. Currently, lowering and maintaining appropriate glucose and HbA_1c levels is the most effective treatment approach. Potential areas of research include alternative medical and surgical treatment interventions for patients while glycemic control is being achieved or for those who fail to benefit from glycemic control alone. Some success has been demonstrated with the use of antidopaminergic medications such as atypical antipsychotics and tetrabenazine and these medications should be considered when tight, sustained glycemic control alone is not successful in treating this disorder in the acute stages. Hopefully, with increasing awareness and recognition of hemiballismus related to hyperglycemia, more large-scale clinical trials can be conducted that will result in an effective treatment strategy for this devastating disorder.

Hemolytic uremic syndrome (HUS) is a rare illness that can be acquired through the consumption of food products contaminated with strains of Shiga toxin-producing Escherichia coli (E coli; STEC).¹ Between 6% and 15% of individuals infected with STEC develop HUS, with children affected more frequently than adults.^2,3 This strain of E coli releases Shiga toxin into the systemic circulation, which causes a thrombotic microangiopathy resulting in the characteristic HUS triad of symptoms: acute renal insufficiency, thrombocytopenia, and hemolytic anemia.^4-6

Although neurologic features are common in HUS, they have not been extensively studied, particularly in adults. We report a case of STEC 0157:H7 subtype HUS in an adult with severe neurologic complications. This case highlights the neurological sequelae in an adult with typical STEC-HUS. The use of treatment modalities, such as plasmapheresis and eculizumab, and their use in adult typical STEC-HUS also is explored.

Case

A 53-year-old white woman with no pertinent past medical history presented to the Bay Pines Veterans Affairs Healthcare System Emergency Department with a 2-day history of abdominal pain, vomiting, nausea, diarrhea, and bright bloody stools. She returned from a cruise to the Bahamas 3 days prior, where she ate local foods, including salads. She reported no fever, shortness of breath, chest pain, headache, and cognitive difficulties. She presented with a normal mental status and neurologic exam. Apart from leukocytosis and elevated glucose level, her laboratory results at initial presentation were normal, (Table). A stool sample showed occult blood with white blood cell counts (WBCs) but was negative for Clostridium difficile. She was started on ciprofloxacin 400 mg and metronidazole 500 mg on the day of admission.

Hematuria was found on hospital day 2. On hospital day 4, the patient exhibited word finding difficulties. Blood studies revealed anemia, thrombocytopenia, leukocytosis, and increasing blood urea nitrogen (BUN) and creatinine. A computed tomography scan of the head was normal. Laboratory analysis showed schistocytes in the peripheral blood smear.

The patient’s cognitive functioning deteriorated on hospital day 5. She was not oriented to time or place. Her laboratory results showed complement level C3 at 70 mg/dL (ref: 83-193 mg/dL) complement C4 at 12 mg/dL (ref: 15-57mg/dL). The patient exhibited oliguria and hyponatremia, as well as both metabolic and respiratory acidosis; dialysis was then initiated. Results from the stool sample that was collected on hospital day 1 were received and tested positive for Shiga toxin.

At this point, the patient’s presentation of hemolytic anemia and thrombocytopenia in the setting of acute bloody diarrheal illness with known Shiga toxin, schistocytes on blood smear, and lack of pertinent medical history for other causes of this presentation made STEC-HUS the leading differential diagnosis. Plasmapheresis was ordered and performed on hospital day 6 and 7. Shiga toxin was no longer detected in the stool and antibiotics were stopped on hospital day 7.

The patient’s progressive deterioration in mental status continued on hospital day 8. She was not oriented to time or place, unable to perform simple calculations, and could not spell the word “hand” backwards. Physicians observed repetitive jerking motions of the upper extremities that were worse on the left side. An electroencephalogram (EEG) revealed right hemispheric sharp waves that were thought to be epileptiform (Figure 1). The patient began taking levetiracetam 1500 mg IV with 750 mg bid maintenance for seizure control. Plasmapheresis was discontinued due to her continued neurologic deterioration on this therapy. Consequently, eculizumab 900 mg IV was given along with the Neisseria meningitidis (N meningitidis) vaccine and a 19-day course of azithromycin 250 mg po as prophylaxis for encapsulated bacteria.

The patient continued to seize on hospital days 10 through 13. Oculocephalic maneuvers showed a tendency to keep her eyes deviated to the right. Her pupils continued to react to light. A repeat EEG showed diffuse slowing (5-6 Hz) with no epileptic activity seen (Figure 2). A second dose of eculizumab 900 mg IV was administered on hospital day 15. The patient experienced cardiac arrest on hospital day 16 and was successfully resuscitated. On hospital day 25 (10 days after receiving her second dose of eculizumab), the patient was able to speak and follow simple commands but exhibited difficulty concentrating and poor impulse control.

The patient was alert and oriented to person, place, time, and situation on hospital day 28 (6 days after the third and final dose of eculizumab). A neurologic exam was significant only for a slight intention tremor. She was continued on levetiracetam with a plan to be maintained on the medication for the next 6 months for seizure control. She was discharged on hospital day 30.

Twenty-eight days postdischarge (57 days postadmission), the patient showed marked recovery. She had returned to her previous employment as a business administrator on a part-time basis and exhibited no deficiencies in executive functioning or handling activities of daily living. Although she had been very active prior to this illness, she now experienced decreased physical and mental endurance; however, this gradually improved with physical therapy. She planned on returning to work on a full-time basis when she had regained her stamina. She also noticed difficulties in retaining short term memory since her discharge but believed that these symptoms were remitting. On examination her mental status and neurologic exam was significant for inability to continue serial 7s, left sided 4/5 muscle strength in quadriceps and thumb to 5th metacarpal adduction, bilateral 1+ reflexes in muscle groups tested (triceps, biceps, brachioradialis, patellar, and Achilles), loss of dull pinprick sensation bilaterally at web of hands, deficit in tandem gait while looking away, and slight intention tremor on finger to nose testing bilaterally (with left hand tremor more pronounced than right). Her complete blood count was normal. Her recovery continues to be monitored in an outpatient setting.

Discussion

HUS is characterized by 3 core clinical features: microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.⁴ Schistocytes are seen on peripheral blood smear and occur due to the passage of red blood cells over the microvascular thrombi induced by the disease. HUS can be classified as typical, atypical, or occurring with a coexisting disease. Typical HUS is associated with STEC 0157:H7 subtype, a bacterium known to be acquired through contaminated food and via human-to-human transmission.^6-8 In the case of typical STEC 0157:H7, the bacterium releases a verotoxin that damages the vascular endothelium, thereby leading to activation of the coagulation cascade and eventually the formation of thrombi.⁴ It has been hypothesized that the Shiga toxin also activates the alternative complement pathway directly, which could contribute to thrombosis.⁹ This would explain the findings of low complement levels in our patient. Atypical HUS is primarily attributable to mutations in the alternative complement pathway. Causes for the third type of HUS can include Streptococcus pneumoniae, HIV, drug toxicity, and alterations in the metabolism of cobalamin C.

Epidemiologically, 15.3% of children aged < 5 years develop typical HUS after exposure to STEC compared with 1.2% of adults aged 18 to 59 years. The median age of patients who developed HUS from STEC exposure was 4 years compared with 16 years for those who did not develop HUS.²

Neurologic manifestations increase mortality for HUS patients.¹⁰ These have been described in the pediatric population as alteration in consciousness (85%), seizures (71%), pyramidal syndrome (52%), and extrapyramidal syndrome with hypertonia (42%).¹¹ Brain imaging in children has demonstrated hemorrhagic lesions involving the pons, basal ganglia, and occipital cortex.¹¹ Blood flow to areas such as the cerebellum, brainstem, and orbitofrontal area can be compromised.¹⁰ Adult patients with HUS can present without lesions on cranial magnetic resonance imaging (MRI), but instead with transient symmetric vasogenic edema of the central brain stem.¹² Unfortunately in this case, MRI was not performed because it was thought to provide limited aid in diagnosis and to avoid unnecessary testing for the acutely ill patient.

The underlying pathophysiology of neurologic manifestations in patients may be due to a metabolic disturbance, toxin-mediated damage of the vascular endothelium, or toxin-induced cytokine release resulting in death of neural cells and subsequent neuroinflammation. However, the most likely mechanism is parenchymal ischemic changes related to microangiopathy.^11,13 Pediatric patients often experience seizures and altered mental status, and their EEGs display delta waves.¹³ This patient’s diffuse slowing on her second EEG and altered mental status suggests that the neuropathologic mechanisms for typical HUS in adults may be similar to those in children.

HUS Treatment

The treatment and management of adults with typical STEC-HUS is evolving. The patient was first suspected to have an infectious colitis and empiric antibiotics were initiated. Some studies suggest that antibiotic administration may worsen the course of HUS in children as it may lead to release and subsequent absorption of Shiga toxin in the intestine.^9,14 However, there is little evidence to suggest harm or efficacy of administration in adults. It is unclear what role antibiotic administration played in the recovery time of HUS given the co-administration of other treatments such as eculizumab and plasmapheresis, but it does appear to have helped with the initial E coli infection.

Plasmapheresis was subsequently administered, due to its documented benefit in the treatment of HUS.¹⁵ However, it should be noted that even though plasmapheresis is currently used in patients with CNS involvement, it remains unproven with conflicting information on its efficacy.^3,16 The mechanism of action is unclear, but it has been hypothesized that plasmapheresis prevents microangiopathy caused by microthrombi.^3,16 For this reason, eculizumab is becoming the mainstay for treatment of STEC-HUS with neurologic complications given the lack of well researched alternative treatments. In this case study, the use of plasmapheresis did not result in clinical improvement, and was abandoned after 2 days of treatment.

Eculizumab is a humanized, recombinant monoclonal IgG antibody that is a terminal complement inhibitor of the alternative complement system at the final step to cleave C5.¹⁷ The Shiga toxin may directly activate the complement system via the alternative pathway, which can result in uncontrolled platelet and white blood cell activation and depletion, endothelial cell damage, and hemolysis. The galvanized complement system leads to a series of cascading events that contribute to organ damage and death.⁹ Eculizumab is FDA approved for use in atypical HUS.¹⁸ It also can be used off-label to treat typical-HUS in adults with neurologic complications.

Eculizumab interferes with the immune response against encapsulated bacteria because it inhibits the alternative complement pathway. Thus, vaccination against N meningitides is recommended 2 weeks prior to the administration of eculizumab. However, in situations where the risks of delaying eculizumab for 2 weeks are greater than the risk of developing an N meningitides infection, eculizumab may be given without delay.¹⁸ Given the rapid deterioration of our patient’s condition, the vaccine and eculizumab were given together with prophylactic azithromycin. Although penicillin is the standard for prophylaxis in this situation, the patient’s penicillin allergy led to the use of azithromycin 250 mg po once a day. Literature also suggests azithromycin reduces the carriage duration of E coli-induced colitis.¹⁹ As such, it is possible that some improvement in the patient’s condition could be attributed to the elimination of the pathogen and toxin.

Conclusion

Three doses of eculizumab were administered at weekly intervals, with the first dose on hospital day 8 and the final dose on hospital day 22. Prior to the first dose, the patient displayed significant decline in mental status with EEG findings of right hemisphere epileptogenic discharges. After her third dose, she was found to have a drastically improved mental status exam and a normal EEG. One week later, she was discharged home. At the time of her 1-month follow-up, she was independent in all activities of daily living and had returned to part-time work. Apart from subtle cognitive changes, the remainder of her neurologic exam was normal.

There is evidence that supports the efficacy of eculizumab in children with HUS with neurologic symptoms on dialysis.²⁰ However, its use in adults is not well established.²¹ This patient required dialysis and had neurologic symptoms similar to pediatric patients described in the literature, and responded similarly to the eculizumab. The rationale for the use of eculizumab in STEC-HUS also is evidenced by in vitro demonstrations of complement activation in STEC-HUS.^22-25 This case report adds to the literature supporting the use of eculizumab in adult patients with typical HUS with neurological complications. Further research is necessary to develop guidelines in the treatment of adult STEC-HUS with regards to neurologic complications.

Acknowledgments

The authors would like to thank Pete DiStaso, REEGT for his work on obtaining the electroencephalograms and Anthony Rinaldi, PsyD; Julie Cessnapalas, PsyD; and Syed Faizan Sagheer for proof-reading the article.

Hemolytic uremic syndrome (HUS) is a rare illness that can be acquired through the consumption of food products contaminated with strains of Shiga toxin-producing Escherichia coli (E coli; STEC).¹ Between 6% and 15% of individuals infected with STEC develop HUS, with children affected more frequently than adults.^2,3 This strain of E coli releases Shiga toxin into the systemic circulation, which causes a thrombotic microangiopathy resulting in the characteristic HUS triad of symptoms: acute renal insufficiency, thrombocytopenia, and hemolytic anemia.^4-6

Although neurologic features are common in HUS, they have not been extensively studied, particularly in adults. We report a case of STEC 0157:H7 subtype HUS in an adult with severe neurologic complications. This case highlights the neurological sequelae in an adult with typical STEC-HUS. The use of treatment modalities, such as plasmapheresis and eculizumab, and their use in adult typical STEC-HUS also is explored.

Case

A 53-year-old white woman with no pertinent past medical history presented to the Bay Pines Veterans Affairs Healthcare System Emergency Department with a 2-day history of abdominal pain, vomiting, nausea, diarrhea, and bright bloody stools. She returned from a cruise to the Bahamas 3 days prior, where she ate local foods, including salads. She reported no fever, shortness of breath, chest pain, headache, and cognitive difficulties. She presented with a normal mental status and neurologic exam. Apart from leukocytosis and elevated glucose level, her laboratory results at initial presentation were normal, (Table). A stool sample showed occult blood with white blood cell counts (WBCs) but was negative for Clostridium difficile. She was started on ciprofloxacin 400 mg and metronidazole 500 mg on the day of admission.

Hematuria was found on hospital day 2. On hospital day 4, the patient exhibited word finding difficulties. Blood studies revealed anemia, thrombocytopenia, leukocytosis, and increasing blood urea nitrogen (BUN) and creatinine. A computed tomography scan of the head was normal. Laboratory analysis showed schistocytes in the peripheral blood smear.

The patient’s cognitive functioning deteriorated on hospital day 5. She was not oriented to time or place. Her laboratory results showed complement level C3 at 70 mg/dL (ref: 83-193 mg/dL) complement C4 at 12 mg/dL (ref: 15-57mg/dL). The patient exhibited oliguria and hyponatremia, as well as both metabolic and respiratory acidosis; dialysis was then initiated. Results from the stool sample that was collected on hospital day 1 were received and tested positive for Shiga toxin.

At this point, the patient’s presentation of hemolytic anemia and thrombocytopenia in the setting of acute bloody diarrheal illness with known Shiga toxin, schistocytes on blood smear, and lack of pertinent medical history for other causes of this presentation made STEC-HUS the leading differential diagnosis. Plasmapheresis was ordered and performed on hospital day 6 and 7. Shiga toxin was no longer detected in the stool and antibiotics were stopped on hospital day 7.

The patient’s progressive deterioration in mental status continued on hospital day 8. She was not oriented to time or place, unable to perform simple calculations, and could not spell the word “hand” backwards. Physicians observed repetitive jerking motions of the upper extremities that were worse on the left side. An electroencephalogram (EEG) revealed right hemispheric sharp waves that were thought to be epileptiform (Figure 1). The patient began taking levetiracetam 1500 mg IV with 750 mg bid maintenance for seizure control. Plasmapheresis was discontinued due to her continued neurologic deterioration on this therapy. Consequently, eculizumab 900 mg IV was given along with the Neisseria meningitidis (N meningitidis) vaccine and a 19-day course of azithromycin 250 mg po as prophylaxis for encapsulated bacteria.

The patient continued to seize on hospital days 10 through 13. Oculocephalic maneuvers showed a tendency to keep her eyes deviated to the right. Her pupils continued to react to light. A repeat EEG showed diffuse slowing (5-6 Hz) with no epileptic activity seen (Figure 2). A second dose of eculizumab 900 mg IV was administered on hospital day 15. The patient experienced cardiac arrest on hospital day 16 and was successfully resuscitated. On hospital day 25 (10 days after receiving her second dose of eculizumab), the patient was able to speak and follow simple commands but exhibited difficulty concentrating and poor impulse control.

The patient was alert and oriented to person, place, time, and situation on hospital day 28 (6 days after the third and final dose of eculizumab). A neurologic exam was significant only for a slight intention tremor. She was continued on levetiracetam with a plan to be maintained on the medication for the next 6 months for seizure control. She was discharged on hospital day 30.

Twenty-eight days postdischarge (57 days postadmission), the patient showed marked recovery. She had returned to her previous employment as a business administrator on a part-time basis and exhibited no deficiencies in executive functioning or handling activities of daily living. Although she had been very active prior to this illness, she now experienced decreased physical and mental endurance; however, this gradually improved with physical therapy. She planned on returning to work on a full-time basis when she had regained her stamina. She also noticed difficulties in retaining short term memory since her discharge but believed that these symptoms were remitting. On examination her mental status and neurologic exam was significant for inability to continue serial 7s, left sided 4/5 muscle strength in quadriceps and thumb to 5th metacarpal adduction, bilateral 1+ reflexes in muscle groups tested (triceps, biceps, brachioradialis, patellar, and Achilles), loss of dull pinprick sensation bilaterally at web of hands, deficit in tandem gait while looking away, and slight intention tremor on finger to nose testing bilaterally (with left hand tremor more pronounced than right). Her complete blood count was normal. Her recovery continues to be monitored in an outpatient setting.

Discussion

HUS is characterized by 3 core clinical features: microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.⁴ Schistocytes are seen on peripheral blood smear and occur due to the passage of red blood cells over the microvascular thrombi induced by the disease. HUS can be classified as typical, atypical, or occurring with a coexisting disease. Typical HUS is associated with STEC 0157:H7 subtype, a bacterium known to be acquired through contaminated food and via human-to-human transmission.^6-8 In the case of typical STEC 0157:H7, the bacterium releases a verotoxin that damages the vascular endothelium, thereby leading to activation of the coagulation cascade and eventually the formation of thrombi.⁴ It has been hypothesized that the Shiga toxin also activates the alternative complement pathway directly, which could contribute to thrombosis.⁹ This would explain the findings of low complement levels in our patient. Atypical HUS is primarily attributable to mutations in the alternative complement pathway. Causes for the third type of HUS can include Streptococcus pneumoniae, HIV, drug toxicity, and alterations in the metabolism of cobalamin C.

Epidemiologically, 15.3% of children aged < 5 years develop typical HUS after exposure to STEC compared with 1.2% of adults aged 18 to 59 years. The median age of patients who developed HUS from STEC exposure was 4 years compared with 16 years for those who did not develop HUS.²

Neurologic manifestations increase mortality for HUS patients.¹⁰ These have been described in the pediatric population as alteration in consciousness (85%), seizures (71%), pyramidal syndrome (52%), and extrapyramidal syndrome with hypertonia (42%).¹¹ Brain imaging in children has demonstrated hemorrhagic lesions involving the pons, basal ganglia, and occipital cortex.¹¹ Blood flow to areas such as the cerebellum, brainstem, and orbitofrontal area can be compromised.¹⁰ Adult patients with HUS can present without lesions on cranial magnetic resonance imaging (MRI), but instead with transient symmetric vasogenic edema of the central brain stem.¹² Unfortunately in this case, MRI was not performed because it was thought to provide limited aid in diagnosis and to avoid unnecessary testing for the acutely ill patient.

The underlying pathophysiology of neurologic manifestations in patients may be due to a metabolic disturbance, toxin-mediated damage of the vascular endothelium, or toxin-induced cytokine release resulting in death of neural cells and subsequent neuroinflammation. However, the most likely mechanism is parenchymal ischemic changes related to microangiopathy.^11,13 Pediatric patients often experience seizures and altered mental status, and their EEGs display delta waves.¹³ This patient’s diffuse slowing on her second EEG and altered mental status suggests that the neuropathologic mechanisms for typical HUS in adults may be similar to those in children.

HUS Treatment

The treatment and management of adults with typical STEC-HUS is evolving. The patient was first suspected to have an infectious colitis and empiric antibiotics were initiated. Some studies suggest that antibiotic administration may worsen the course of HUS in children as it may lead to release and subsequent absorption of Shiga toxin in the intestine.^9,14 However, there is little evidence to suggest harm or efficacy of administration in adults. It is unclear what role antibiotic administration played in the recovery time of HUS given the co-administration of other treatments such as eculizumab and plasmapheresis, but it does appear to have helped with the initial E coli infection.

Plasmapheresis was subsequently administered, due to its documented benefit in the treatment of HUS.¹⁵ However, it should be noted that even though plasmapheresis is currently used in patients with CNS involvement, it remains unproven with conflicting information on its efficacy.^3,16 The mechanism of action is unclear, but it has been hypothesized that plasmapheresis prevents microangiopathy caused by microthrombi.^3,16 For this reason, eculizumab is becoming the mainstay for treatment of STEC-HUS with neurologic complications given the lack of well researched alternative treatments. In this case study, the use of plasmapheresis did not result in clinical improvement, and was abandoned after 2 days of treatment.

Eculizumab is a humanized, recombinant monoclonal IgG antibody that is a terminal complement inhibitor of the alternative complement system at the final step to cleave C5.¹⁷ The Shiga toxin may directly activate the complement system via the alternative pathway, which can result in uncontrolled platelet and white blood cell activation and depletion, endothelial cell damage, and hemolysis. The galvanized complement system leads to a series of cascading events that contribute to organ damage and death.⁹ Eculizumab is FDA approved for use in atypical HUS.¹⁸ It also can be used off-label to treat typical-HUS in adults with neurologic complications.

Eculizumab interferes with the immune response against encapsulated bacteria because it inhibits the alternative complement pathway. Thus, vaccination against N meningitides is recommended 2 weeks prior to the administration of eculizumab. However, in situations where the risks of delaying eculizumab for 2 weeks are greater than the risk of developing an N meningitides infection, eculizumab may be given without delay.¹⁸ Given the rapid deterioration of our patient’s condition, the vaccine and eculizumab were given together with prophylactic azithromycin. Although penicillin is the standard for prophylaxis in this situation, the patient’s penicillin allergy led to the use of azithromycin 250 mg po once a day. Literature also suggests azithromycin reduces the carriage duration of E coli-induced colitis.¹⁹ As such, it is possible that some improvement in the patient’s condition could be attributed to the elimination of the pathogen and toxin.

Conclusion

Three doses of eculizumab were administered at weekly intervals, with the first dose on hospital day 8 and the final dose on hospital day 22. Prior to the first dose, the patient displayed significant decline in mental status with EEG findings of right hemisphere epileptogenic discharges. After her third dose, she was found to have a drastically improved mental status exam and a normal EEG. One week later, she was discharged home. At the time of her 1-month follow-up, she was independent in all activities of daily living and had returned to part-time work. Apart from subtle cognitive changes, the remainder of her neurologic exam was normal.

There is evidence that supports the efficacy of eculizumab in children with HUS with neurologic symptoms on dialysis.²⁰ However, its use in adults is not well established.²¹ This patient required dialysis and had neurologic symptoms similar to pediatric patients described in the literature, and responded similarly to the eculizumab. The rationale for the use of eculizumab in STEC-HUS also is evidenced by in vitro demonstrations of complement activation in STEC-HUS.^22-25 This case report adds to the literature supporting the use of eculizumab in adult patients with typical HUS with neurological complications. Further research is necessary to develop guidelines in the treatment of adult STEC-HUS with regards to neurologic complications.

Acknowledgments

The authors would like to thank Pete DiStaso, REEGT for his work on obtaining the electroencephalograms and Anthony Rinaldi, PsyD; Julie Cessnapalas, PsyD; and Syed Faizan Sagheer for proof-reading the article.

Hemolytic uremic syndrome (HUS) is a rare illness that can be acquired through the consumption of food products contaminated with strains of Shiga toxin-producing Escherichia coli (E coli; STEC).¹ Between 6% and 15% of individuals infected with STEC develop HUS, with children affected more frequently than adults.^2,3 This strain of E coli releases Shiga toxin into the systemic circulation, which causes a thrombotic microangiopathy resulting in the characteristic HUS triad of symptoms: acute renal insufficiency, thrombocytopenia, and hemolytic anemia.^4-6

Although neurologic features are common in HUS, they have not been extensively studied, particularly in adults. We report a case of STEC 0157:H7 subtype HUS in an adult with severe neurologic complications. This case highlights the neurological sequelae in an adult with typical STEC-HUS. The use of treatment modalities, such as plasmapheresis and eculizumab, and their use in adult typical STEC-HUS also is explored.

Case

A 53-year-old white woman with no pertinent past medical history presented to the Bay Pines Veterans Affairs Healthcare System Emergency Department with a 2-day history of abdominal pain, vomiting, nausea, diarrhea, and bright bloody stools. She returned from a cruise to the Bahamas 3 days prior, where she ate local foods, including salads. She reported no fever, shortness of breath, chest pain, headache, and cognitive difficulties. She presented with a normal mental status and neurologic exam. Apart from leukocytosis and elevated glucose level, her laboratory results at initial presentation were normal, (Table). A stool sample showed occult blood with white blood cell counts (WBCs) but was negative for Clostridium difficile. She was started on ciprofloxacin 400 mg and metronidazole 500 mg on the day of admission.

Hematuria was found on hospital day 2. On hospital day 4, the patient exhibited word finding difficulties. Blood studies revealed anemia, thrombocytopenia, leukocytosis, and increasing blood urea nitrogen (BUN) and creatinine. A computed tomography scan of the head was normal. Laboratory analysis showed schistocytes in the peripheral blood smear.

The patient’s cognitive functioning deteriorated on hospital day 5. She was not oriented to time or place. Her laboratory results showed complement level C3 at 70 mg/dL (ref: 83-193 mg/dL) complement C4 at 12 mg/dL (ref: 15-57mg/dL). The patient exhibited oliguria and hyponatremia, as well as both metabolic and respiratory acidosis; dialysis was then initiated. Results from the stool sample that was collected on hospital day 1 were received and tested positive for Shiga toxin.

At this point, the patient’s presentation of hemolytic anemia and thrombocytopenia in the setting of acute bloody diarrheal illness with known Shiga toxin, schistocytes on blood smear, and lack of pertinent medical history for other causes of this presentation made STEC-HUS the leading differential diagnosis. Plasmapheresis was ordered and performed on hospital day 6 and 7. Shiga toxin was no longer detected in the stool and antibiotics were stopped on hospital day 7.

The patient’s progressive deterioration in mental status continued on hospital day 8. She was not oriented to time or place, unable to perform simple calculations, and could not spell the word “hand” backwards. Physicians observed repetitive jerking motions of the upper extremities that were worse on the left side. An electroencephalogram (EEG) revealed right hemispheric sharp waves that were thought to be epileptiform (Figure 1). The patient began taking levetiracetam 1500 mg IV with 750 mg bid maintenance for seizure control. Plasmapheresis was discontinued due to her continued neurologic deterioration on this therapy. Consequently, eculizumab 900 mg IV was given along with the Neisseria meningitidis (N meningitidis) vaccine and a 19-day course of azithromycin 250 mg po as prophylaxis for encapsulated bacteria.

The patient continued to seize on hospital days 10 through 13. Oculocephalic maneuvers showed a tendency to keep her eyes deviated to the right. Her pupils continued to react to light. A repeat EEG showed diffuse slowing (5-6 Hz) with no epileptic activity seen (Figure 2). A second dose of eculizumab 900 mg IV was administered on hospital day 15. The patient experienced cardiac arrest on hospital day 16 and was successfully resuscitated. On hospital day 25 (10 days after receiving her second dose of eculizumab), the patient was able to speak and follow simple commands but exhibited difficulty concentrating and poor impulse control.

The patient was alert and oriented to person, place, time, and situation on hospital day 28 (6 days after the third and final dose of eculizumab). A neurologic exam was significant only for a slight intention tremor. She was continued on levetiracetam with a plan to be maintained on the medication for the next 6 months for seizure control. She was discharged on hospital day 30.

Twenty-eight days postdischarge (57 days postadmission), the patient showed marked recovery. She had returned to her previous employment as a business administrator on a part-time basis and exhibited no deficiencies in executive functioning or handling activities of daily living. Although she had been very active prior to this illness, she now experienced decreased physical and mental endurance; however, this gradually improved with physical therapy. She planned on returning to work on a full-time basis when she had regained her stamina. She also noticed difficulties in retaining short term memory since her discharge but believed that these symptoms were remitting. On examination her mental status and neurologic exam was significant for inability to continue serial 7s, left sided 4/5 muscle strength in quadriceps and thumb to 5th metacarpal adduction, bilateral 1+ reflexes in muscle groups tested (triceps, biceps, brachioradialis, patellar, and Achilles), loss of dull pinprick sensation bilaterally at web of hands, deficit in tandem gait while looking away, and slight intention tremor on finger to nose testing bilaterally (with left hand tremor more pronounced than right). Her complete blood count was normal. Her recovery continues to be monitored in an outpatient setting.

Discussion

HUS is characterized by 3 core clinical features: microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury.⁴ Schistocytes are seen on peripheral blood smear and occur due to the passage of red blood cells over the microvascular thrombi induced by the disease. HUS can be classified as typical, atypical, or occurring with a coexisting disease. Typical HUS is associated with STEC 0157:H7 subtype, a bacterium known to be acquired through contaminated food and via human-to-human transmission.^6-8 In the case of typical STEC 0157:H7, the bacterium releases a verotoxin that damages the vascular endothelium, thereby leading to activation of the coagulation cascade and eventually the formation of thrombi.⁴ It has been hypothesized that the Shiga toxin also activates the alternative complement pathway directly, which could contribute to thrombosis.⁹ This would explain the findings of low complement levels in our patient. Atypical HUS is primarily attributable to mutations in the alternative complement pathway. Causes for the third type of HUS can include Streptococcus pneumoniae, HIV, drug toxicity, and alterations in the metabolism of cobalamin C.

Epidemiologically, 15.3% of children aged < 5 years develop typical HUS after exposure to STEC compared with 1.2% of adults aged 18 to 59 years. The median age of patients who developed HUS from STEC exposure was 4 years compared with 16 years for those who did not develop HUS.²

Neurologic manifestations increase mortality for HUS patients.¹⁰ These have been described in the pediatric population as alteration in consciousness (85%), seizures (71%), pyramidal syndrome (52%), and extrapyramidal syndrome with hypertonia (42%).¹¹ Brain imaging in children has demonstrated hemorrhagic lesions involving the pons, basal ganglia, and occipital cortex.¹¹ Blood flow to areas such as the cerebellum, brainstem, and orbitofrontal area can be compromised.¹⁰ Adult patients with HUS can present without lesions on cranial magnetic resonance imaging (MRI), but instead with transient symmetric vasogenic edema of the central brain stem.¹² Unfortunately in this case, MRI was not performed because it was thought to provide limited aid in diagnosis and to avoid unnecessary testing for the acutely ill patient.

The underlying pathophysiology of neurologic manifestations in patients may be due to a metabolic disturbance, toxin-mediated damage of the vascular endothelium, or toxin-induced cytokine release resulting in death of neural cells and subsequent neuroinflammation. However, the most likely mechanism is parenchymal ischemic changes related to microangiopathy.^11,13 Pediatric patients often experience seizures and altered mental status, and their EEGs display delta waves.¹³ This patient’s diffuse slowing on her second EEG and altered mental status suggests that the neuropathologic mechanisms for typical HUS in adults may be similar to those in children.

HUS Treatment

The treatment and management of adults with typical STEC-HUS is evolving. The patient was first suspected to have an infectious colitis and empiric antibiotics were initiated. Some studies suggest that antibiotic administration may worsen the course of HUS in children as it may lead to release and subsequent absorption of Shiga toxin in the intestine.^9,14 However, there is little evidence to suggest harm or efficacy of administration in adults. It is unclear what role antibiotic administration played in the recovery time of HUS given the co-administration of other treatments such as eculizumab and plasmapheresis, but it does appear to have helped with the initial E coli infection.

Plasmapheresis was subsequently administered, due to its documented benefit in the treatment of HUS.¹⁵ However, it should be noted that even though plasmapheresis is currently used in patients with CNS involvement, it remains unproven with conflicting information on its efficacy.^3,16 The mechanism of action is unclear, but it has been hypothesized that plasmapheresis prevents microangiopathy caused by microthrombi.^3,16 For this reason, eculizumab is becoming the mainstay for treatment of STEC-HUS with neurologic complications given the lack of well researched alternative treatments. In this case study, the use of plasmapheresis did not result in clinical improvement, and was abandoned after 2 days of treatment.

Eculizumab is a humanized, recombinant monoclonal IgG antibody that is a terminal complement inhibitor of the alternative complement system at the final step to cleave C5.¹⁷ The Shiga toxin may directly activate the complement system via the alternative pathway, which can result in uncontrolled platelet and white blood cell activation and depletion, endothelial cell damage, and hemolysis. The galvanized complement system leads to a series of cascading events that contribute to organ damage and death.⁹ Eculizumab is FDA approved for use in atypical HUS.¹⁸ It also can be used off-label to treat typical-HUS in adults with neurologic complications.

Eculizumab interferes with the immune response against encapsulated bacteria because it inhibits the alternative complement pathway. Thus, vaccination against N meningitides is recommended 2 weeks prior to the administration of eculizumab. However, in situations where the risks of delaying eculizumab for 2 weeks are greater than the risk of developing an N meningitides infection, eculizumab may be given without delay.¹⁸ Given the rapid deterioration of our patient’s condition, the vaccine and eculizumab were given together with prophylactic azithromycin. Although penicillin is the standard for prophylaxis in this situation, the patient’s penicillin allergy led to the use of azithromycin 250 mg po once a day. Literature also suggests azithromycin reduces the carriage duration of E coli-induced colitis.¹⁹ As such, it is possible that some improvement in the patient’s condition could be attributed to the elimination of the pathogen and toxin.

Conclusion

Three doses of eculizumab were administered at weekly intervals, with the first dose on hospital day 8 and the final dose on hospital day 22. Prior to the first dose, the patient displayed significant decline in mental status with EEG findings of right hemisphere epileptogenic discharges. After her third dose, she was found to have a drastically improved mental status exam and a normal EEG. One week later, she was discharged home. At the time of her 1-month follow-up, she was independent in all activities of daily living and had returned to part-time work. Apart from subtle cognitive changes, the remainder of her neurologic exam was normal.

There is evidence that supports the efficacy of eculizumab in children with HUS with neurologic symptoms on dialysis.²⁰ However, its use in adults is not well established.²¹ This patient required dialysis and had neurologic symptoms similar to pediatric patients described in the literature, and responded similarly to the eculizumab. The rationale for the use of eculizumab in STEC-HUS also is evidenced by in vitro demonstrations of complement activation in STEC-HUS.^22-25 This case report adds to the literature supporting the use of eculizumab in adult patients with typical HUS with neurological complications. Further research is necessary to develop guidelines in the treatment of adult STEC-HUS with regards to neurologic complications.

Acknowledgments

The authors would like to thank Pete DiStaso, REEGT for his work on obtaining the electroencephalograms and Anthony Rinaldi, PsyD; Julie Cessnapalas, PsyD; and Syed Faizan Sagheer for proof-reading the article.