Test your skills: Which imaging studies would you order for these neurologic complaints?

›› And you order...

…an MRI of the brain with contrast.

Though Ms. D does have a focal neurologic finding in addition to her headache, she does not appear to be acutely ill. Ordering an MRI with contrast is the best first step.

Patients with isolated headache and no other symptoms on neurologic exam are unlikely to have a significant intracranial abnormality.

CASE 2 › Anne B is a 72-year-old woman with a history of hypertension, hyperlipidemia, and type 2 diabetes. Her daughter brings her in to see you because she is concerned about Ms. B’s memory. Ms. B’s daughter reports that she has become increasingly forgetful over the past 6 months, often forgetting recent events. At first the forgetfulness was occasional, but now it seems to happen daily and interfere with activities of daily living (ADLs). The week before this visit, Ms. B left a pot heating on the stove because she forgot she had started cooking. She realized what had happened only when her smoke alarm went off. Ms. B’s daughter also thinks her mother may be taking some of her medications incorrectly.

Physical exam and laboratory findings are unremarkable. On the mental status exam, Ms. B has difficulty with registration and recall.

›› What imaging options might you consider?

Ms. B has exhibited progressive memory loss over 6 months and it is now affecting her ADLs. Her symptoms could be secondary to any one of many reversible medical causes, such as adverse medication effects, depression, or vitamin B12 deficiency. If clinical and laboratory evaluations exclude these reversible causes, consider dementia.

With numerous disorders having overlapping symptoms, the diagnosis of degenerative central nervous system (CNS) disease can be extremely tricky. Complicating the issue is the fact that a single patient can have 2 or more concurrent neurodegenerative diseases. Clinical testing is essential in the diagnosis and management of degenerative CNS diseases, but testing sensitivity and specificity are highly variable depending upon the disease.¹⁴

Neuroimaging is an important supplement to clinical testing in excluding intracranial abnormalities. There are significant negative consequences of missing reversible causes of memory problems and incorrectly assigning a clinical diagnosis of dementia. Neuroimaging can be subdivided into structural and functional imaging, and structural imaging is the first step in evaluation.¹⁵

The American Academy of Neurology recommends the use of structural neuroimaging with CT or MRI in the initial evaluation of patients with dementia to detect such treatable problems as a subdural hematoma, frontal lobe mass, or hydrocephalus.¹² Structural imaging may also identify anatomic changes characteristic of degenerative CNS diseases such as Alzheimer’s disease, dementia with Lewy bodies, frontotemporal dementia, vascular dementia, Creutzfeldt-Jakob disease, and Huntington’s disease; however, sensitivities and specificities of testing are low.¹⁴

›› And you order...

…an MRI of the brain without contrast.

In Ms. B’s case, structural neuroimaging is indicated as part of the initial work-up of supposed dementia. An MRI without contrast is recommended over CT because it is more sensitive in detecting white matter changes in vascular dementia.¹⁶ In cases where an MRI >is unavailable or contraindicated (eg, a patient with a pacemaker), a CT is a reasonable alternative.

CASE 3 › Bob C is a 78-year-old man with a history of chronic obstructive pulmonary disease and hypertension who arrives at your walk-in clinic accompanied by his home health aide a few hours after having tripped and fallen over a rug at home. At baseline, Mr. C is ambulatory and independent in ADLs.

He takes all of his medications, including a daily baby aspirin (81 mg). Mr. C says he did not lose consciousness at the time of the fall and insists he feels fine, but you notice a bruise developing over his right temporal skull.

›› What imaging options might you consider?

With acute head trauma deemed severe enough clinically to warrant imaging, non-contrast CT is the most appropriate initial test to identify possible intracranial hemorrhage.¹¹ The Glasgow Coma Scale (GCS) is the tool most widely used for clinical evaluation¹⁷ (TABLE 1¹⁸). The score is based on an assessment of 3 features: eye response, speech, and movement. Head injury is classified as mild (13-15), moderate (9-12), or severe (≤8). It is universally agreed that patients with moderate or severe head injury should be further evaluated with a head CT.

With mild head injury, recommendations for follow-up are less straightforward. The New Orleans Criteria (NOC) and Canadian CT Head Rule (CCHR) are commonly used in triaging patients with minor head trauma in a cost effective way¹¹ (TABLES 2¹⁹ and 3²⁰). The cost-effectiveness of these assessment tools is still questionable, but both have very high sensitivity for identifying patients who will require neurosurgery intervention.^21,22 Although the NOC is slightly more sensitive at identifying patients with nonsurgical clinically significant abnormalities, it has a greatly reduced specificity compared with the CCHR.^23-25