A 56-year-old man with a history of cigarette smoking was admitted to our intensive care department for pneumonia-related oxygen dependence. Two weeks previously (during a vacation in the countryside), the patient had developed confusion, headaches with photophobia, diplopia and fever. A neurological examination revealed drowsiness and binocular diplopia caused by left sixth cranial nerve palsy (Fig. 1a, b). Following lumbar puncture, bacterial cultures and PCR assays of the cerebrospinal fluid were negative. Magnetic resonance imaging of the brain was unremarkable.