Introduction: 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 two 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.

Methods: We retrospectively reviewed case histories from a large series of adults with MM who were treated at our institution, to identify those in whom an initial diagnosis of MS had been made.

Results: The patients ranged in age from 15 to 42 years at symptom onset (n=11), and 10 were female. All experienced transient neurological symptoms of one kind or another at onset, and headache was present in 7. The initial diagnosis was MS in 9, and MS vs. ADEM in 2. Five received active treatment for their MS diagnosis, including beta-interferon, glatiramer acetate, and corticosteroids. The delay from symptom onset to MM diagnosis ranged from 2 months to 19 years, with a mean and median delay both equal to 4 years. Five have been left with ongoing neurologic symptoms and/or disability that might arguably have been preventable.

Conclusions: MM can be misdiagnosed as MS, leading to delay in correct treatment. We highlight the clinical and radiological features which allow differentiation of these conditions early in the course, when treatment can have maximum benefit.

Patient Care: Heightened awareness of moyamoya as a differential diagnostic consideration, and careful analysis of the clinical and radiological features of each case, will help to minimize misdiagnosis and treatment delay of those with clinical symptoms commonly associated with multiple sclerosis.

Learning Objectives: Participants will be able to identify clinical and radiological characteristics to differentiate moyamoya disease from multiple sclerosis.

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