An 83-year-old man with diabetes was admitted for excessive daytime sleepiness that began 2 weeks previously after he sustained a fall and concussion. He had a past history of multiple myeloma with a solitary skull lesion, requiring local radiotherapy. CT and MRI scans showed mild diffuse cerebral atrophy and the known skull lesion at the vertex (fig 1B, C). Blood biochemistry was normal. Psychiatric evaluation ruled out depression. EEG …