A 93-year-old bedbound woman with cognitive impairment was admitted with a 1-day history of herpes zoster (HZ) infection in the right S1/2 dermatomes, followed by fever and drowsiness. Physical examination revealed no neck stiffness, meningism or focal signs. Blood tests showed hypoalbuminaemia and lymphopenia. Conventional brain magnetic resonance imaging (MRI) revealed hippocampal atrophy and diffusion weighted imaging showed no acute infarctions. A polymerase chain reaction DNA microassay test of the cerebrospinal fluid (CSF) was positive for varicella zoster virus. The patient received acyclovir intravenously, with a favourable clinical course...