No vaccine-no protection: mumps meningoencephalitis and hydrocephalus in an unvaccinated adult.

Mumps virus is a rare cause of hydrocephalus. A non-immunised, healthy 23 year-old male presented to the Emergency Department, 12 days after diagnosis of mumps parotitis. He reported a gradual improvement until the onset of headache and vomiting 48 hours earlier. He had never been immunised, having been born prior to implementation of the Irish measles, mumps and rubella (MMR) vaccination programme in 1986. He was afebrile, normotensive, bradycardic, disoriented in time and examination, including fundoscopy was normal. Computerised tomography (CT) scan of the head revealed marked dilatation of the lateral and third ventricles, with early sub-ependymal oedema adjacent to the temporal and frontal horns of the lateral ventricles. The basal cisterns remained patent. The fourth ventricle was normal in size, suggesting that ventricular enlargement was due to aqueductal stenosis.