Intractable epilepsy and progressive cognitive decline in a young man

A young man with normal neurodevelopment presented with 3 years of medically refractory, progressive epilepsy and myoclonus. Initial examination included neuroimaging, electroencephalography, and biochemical analyses, all of which were unremarkable except for mildly enlarged ventricles. Over the following year, the patient experienced rapid cognitive decline with new-onset recurrent visual hallucinations and progressive lethargy. Results of subsequent electroencephalography and brain imaging were unchanged, and a fluorodeoxyglucose F 18 positron emission tomographic scan was normal.