Acute behavioural change in a young woman evolving towards cerebellar syndrome.

Symptomatic paraneoplastic neurological syndromes are rare manifestations of cancers. Recently, a new type of encephalitis associated with antibodies against NMDA-glutamate receptors (A-NMDAR) was defined. The patients, usually young women, present with acute onset of psychiatric symptoms and decreased consciousness. We describe the case of a patient who presented with acute onset of delirium alternating with sub-comatose state. Blood analyses were within normal range. Lumbar puncture showed lymphocytic pleiocytosis. Brain gadolinium injected MRI, brain and full body PET scans were normal. Investigations led to suspect a paraneoplastic syndrome and a right ovarian teratoma and A-NMDAR were found and the teratoma removed. The remaining sequellae included a cerebellar syndrome seldom described before. As cerebellar and cortical neurons share the same excitatory pathway through NMDA-glutamate receptors, the cerebellar function impairment observed in our patient could be explained by a disabling action on glutamate NMDAR by the A-NMDAR.