Moyamoya disease can masquerade as multiple sclerosis

BACKGROUND:: Moyamoya disease (MM) is a rare disorder of the cerebral arterial circulation, whereas multiple sclerosis (MS) is a relatively common immune-mediated attack on central myelin. Despite the differences in pathogenesis, the 2 disorders share some clinical features which can lead to diagnostic confusion: both can affect young adults, cause intermittent neurological symptoms, and show multifocal abnormalities on brain imaging. OBJECTIVE:: To emphasize the need for early consideration of MM in the differential diagnosis of MS-spectrum disorders. METHODS:: Chart reviews and individual case analyses. RESULTS:: We present detailed descriptions of 3 patients with MM, and summary data on 8 additional cases, in which there was diagnostic confusion with MS, with delays in treatment ranging from 2 months to 19 years (median=4 y). CONCLUSIONS:: MM can be misdiagnosed as MS, leading to delay in correct treatment. We highlight the clinical and radiologic features which allow differentiation of these conditions early in the course, when treatment can have maximum benefit.