Gliomatosis cerebri may present as an atypical parkinsonian syndrome.

An 85-year-old man presented with 3 years of a progressive akinetic rigid syndrome with ataxia, falls, levodopa unresponsiveness, and autonomic dysfunction. Early in the course of illness, cranial magnetic resonance imaging (MRI) was thought to show pontine enlargement but later was reinterpreted by experts as normal. Two subsequent cranial MRIs were believed to show only mild atrophy. An initial clinical diagnosis of multiple system atrophy was made. The patient died 4 years after the onset of symptoms. Pathological examination revealed diffuse infiltration of multiple brain regions with cells of astrocytic and microglial origin consistent with a diagnosis of gliomatosis cerebri.