CNS inflammation other than multiple sclerosis: how likely is diagnosis?

The incidence, diagnostic landscape, and workload impact of CNS inflammatory diseases other than multiple sclerosis (MS) (CIDOMS) in a tertiary setting is unknown. We describe a retrospective case series of 64 patients identified over a 2-year period (2009–2010) at the Wessex Neurological Centre in the United Kingdom, accounting for 4% of all patients seen at the center. As expected, neurosarcoidosis and neuromyelitis optica (NMO) were the most common diagnoses reached (14% each); other diagnoses singly accounted for <10%. However, the likeliest diagnostic outcome (strikingly, in 25%) was nondiagnosis, despite intensive investigation and a mean follow-up period of 3 years. Undiagnosed patients with CIDOMS represented the largest workload of the neurology center.