In contrast, the World Health Organization’s ICD-10 Classification of Mental and Behavioural Disorders groups diagnostic criteria for FND among the dissociative disorders13:
- Clinical features are specified for the individual dissociative disorder (motor, sensory, convulsions, mixed).
- Evidence is absent of a physical disorder that might explain symptoms.
- Evidence of psychological causation is present in clear temporal association with stressful events and problems or disturbed relationships, even if the patient denies such association.
Note the emphasis on psychological causation and exclusion of purposeful simulation of symptoms, as opposed to a primarily unconscious disconnection from the patient’s body or environment.
ICD-10 guidelines acknowledge the difficulty of finding definitive evidence of a psychological cause and recommend provisional diagnosis of FND if psychological factors are not readily apparent.14 Of note, many patients with FND are affected psychologically by their condition, with an impact on mood, behaviors, and interpersonal interactions, although not necessarily to a clinically diagnostic degree. Therefore, a psychiatric diagnosis alone is not a necessary precursor for the diagnosis of an FND.
CASE
History. Mr. D’s history is positive for light alcohol consumption (“2 or 3 cans of beer on weekends”) and chewing tobacco (he reports stopping 6 months earlier) and negative for substance abuse. The family history is positive for maternal hypertension and paternal suicide when the patient was 10 years old (no other known paternal history).
Physical findings. The review of systems is positive for intermittent palpitations, lower-extremity weakness causing unsteady gait, and generalized headache.
Vital signs are within normal limits, including blood pressure (120/82 mm Hg) and heart rate (110 beats/min). The patient is not in acute distress; he is awake, alert, and oriented × 3. No murmurs are heard; lungs are clear bilaterally to auscultation. There is no tenderness on abdominal palpation, and no hepatomegaly or splenomegaly; bowel sounds are normal. No significant bruising or lacerations are noted.
Neurology exam. Cranial nerves II-XII are intact. Pupils are equal and reactive to light. Reflexes are 2+ bilaterally. Muscle strength and tone are normal; no tremors are noted. Babinski signs are normal. A Romberg test is positive (swaying).
Continue to: Mr. D has an antalgic gait...