Slowly progressive ataxia, neuropathy, and oculomotor dysfunction

A 54-year-old white man presented with slowly progressive incoordination and weakness. He had normal motor development until, at 16 years of age, he noted difficulty walking and difficulty reading despite normal visual acuity. By the fourth decade of life, he developed poor coordination and balance, as well as inability to walk. In subsequent years, he developed progressive, painless sensory loss, weakness, and atrophy in his distal arms and legs. His vision problems progressed and he also developed dysarthria without dysphagia. Family history was negative except for an uncle who was described as "clumsy." Results of an oculomotor examination were notable for increased square-wave jerks, persistent bilateral gazeevoked nystagmus with saccadic pursuit, intact vestibulo-ocular reflex, and saccadic dysmetria. He had a mixed dysarthria with flaccid and ataxic characteristics and severe weakness and atrophy in the distal limb muscles. Sensation was diminished to the midforearms and midthighs in all modalities. Deep tendon reflexes were absent throughout, with no response to plantar stimulation. He had marked appendicular ataxia with mild axial ataxia. Magnetic resonance imaging of the brain revealed severe cerebellar atrophy. Results of an electrodiagnostic study suggested a severe axonal sensorimotor polyneuropathy with active and chronic denervation. The differential diagnosis in a patient with ataxia, neuropathy, and oculomotor features is discussed; a methodical approach to the diagnostic workup is suggested; and the final diagnosis is revealed.