Leukoencephalopathy associated with cobalamin deficiency

Cobalamin (vitamin B₁₂) deficiency may produce cognitive and neuropsychiatric manifestations. ^[1,2] The symptoms, which may be subtle and arise from atypical causes of cobalamin deficiency, ^[3] are assumed to be reversible and produced by white matter abnormalities. Despite the presumed central myelin etiopathogenesis of cognitive impairment in this disorder, ^[3] white matter abnormalities on brain imaging are rarely reported, ^[4] and the effects of cobalamin replacement therapy on such structural abnormalities are not known. We describe a patient with cobalamin deficiency who presented with subacute onset of cognitive impairment and marked white matter abnormalities on brain MRI and report the changes in both his cognitive abilities and MRI in response to therapy.

Case report.

A 76-year-old right-handed man with a history of hypertension, atrial fibrillation, hypothyroidism, and remote colon cancer was admitted because of a 6-month history of increasing forgetfulness, reading difficulty, and problems balancing his checkbook. He also complained of headaches, fatigue, weight loss, visual impairment, and gait abnormalities. His medications included enalapril, digoxin, warfarin, levothyroxine, and allopurinol. He had no history of tobacco or alcohol use.

An initial mental status examination revealed a forward span of six digits and an inability to count backwards or state the days of the week backwards. He was unable to remember any of three words or any of 10 items in a short story after a delay. Spontaneous speech, naming, and repetition were normal. He could not count identical dots arrayed randomly in front of him or copy intersecting pentagons or a cube. Visually guided limb movements were slow but accurate, and his praxis performance of transitive limb gestures to command was normal. He had bilateral …