A 52 year old man presented with status epilepticus. He had been previously well but smoked 10 cigarettes a day. When his seizures subsided he was noted to have a major amnesic syndrome. Brain CT and CSF examination (including polymerase chain reaction for herpes simplex) were normal, as were a full haematological and biochemical screen. Psychometric testing disclosed a mini mental test score of 12/30 with a pronounced deficit in short term memory. Neurological examination was otherwise normal. EEG disclosed bilateral excess of slow activity.

• Download figure
• Open in new tab
• Download powerpoint

Unenhanced MRI axial T2 and FLAIR sequences (figure, A) showed abnormal bilateral symmetric high signal within the limbic system, thought to be compatible with a paraneoplastic limbic encephalitis.1Chest radiography was normal, and anti-Hu and anti-Yo antibodies were negative. A chest CT (figure,B) showed subcarinal lymphadenopathy (arrow) with normal lung fields.

Small cell carcinoma of the lung was confirmed after thoracoscopy and subcarinal lymph node biopsy. He completed three cycles of chemotherapy with mitomycin C, vinblastine, and cisplatin, without any apparent change in his cognitive state. Repeat MRI at six weeks showed only minimal change in the signal abnormality.

The patient subsequently had a fatal pulmonary embolus. Post mortem examination was declined.