The topographic diagnosis of acquired nystagmus in brainstem disorders

Downbeat nystagmus following classical heat stroke

Cerebellar syndrome following classical heat stroke is rare. We report a case of a 39-year-old man who presented with a cerebellar syndrome including downbeat nystagmus. MRI taken after 3 days of admission was normal. The downbeat nystagmus lasted for 6 days and than gradually disappeared. The ataxia and dysmetria improved gradually over 2 months. A brain CT scan performed 3 months later revealed no cerebellar atrophy. This case is unique as there were no predisposing factors (e.g. hypomagnesemia) and follow-up revealed complete reversibility of the ophthalmological abnormality. It reveals that the vestibulocerebellum is particularly vulnerable to thermal injury.

Presumed pharmacologically induced change from upbeat- to downbeat nystagmus in a patient with Wernicke’s encephalopathy

A case of Wernicke's encephalopathy due to proven thiamine deficiency suffering from upbeat nystagmus (UN) changing to downbeat nystagmus (DN) after a latency of 1 year is presented. The case was also notable for the finding of positive oligoclonal bands in the CSF. The underlying pathophysiological mechanisms and a possible effect of baclofen treatment are discussed.