Clinical Reasoning: A 57-year-old woman with progressive ataxia and falls

A 57-year-old woman presented with progressive ataxia and falls. She was in her usual state of health until she developed sudden onset of progressive imbalance for a month. She then presented to an emergency department. Examination revealed significant vibration sensation impairment and proprioceptive loss, with normal pinprick and temperature sensation; sensory ataxia with pseudoathetosis in the hands; no finger to nose incoordination; normal rapid alternating movements of upper extremities; heel to shin incoordination; diminished deep tendon reflexes; wide-based gait; and positive Romberg test. She did not have cognitive impairment, nystagmus, dysarthria, weakness, muscle atrophy, or fasciculations.