Atypical and clinically silent multiple sclerosis: a report of 12 cases discovered unexpectedly at necropsy.

Twelve cases are reported in which multiple sclerosis was discovered unexpectedly at necropsy. Four of the patients had no known previous history of neurological illness, four did have a previous neurological or neuropsychiatric disturbance, but multiple sclerosis was never entertained in the differential diagnosis and four had a history of disorder in the nervous system, but a diagnosis of multiple sclerosis was either rejected or regarded as unlikely. In six of the eight patients with a previous history of neurological illness the onset was at or over the age of 50 years. Computed tomography and measurement of evoked responses should now reduce the number of undiagnosed cases, but some will inevitably remain, giving rise to an underestimate of disease prevalence.