Background: The first ever diagnosis of multiple sclerosis (MS) requires consideration of both diagnostic criteria and differential diagnosis. Clinicians are particularly challenged by rare conditions which may mimic MS symptoms and relapses.
Case report: We report the case of a young female patient who presented with relapsing left hemispheric symptoms that were highly suspicious of MS but were caused by an idiopathic occlusive angiopathy of the circle of Willis.
Conclusion: Occlusive disease of the great cerebral arteries in young patients is a rare but important differential diagnosis of MS. It has to be considered in patients presenting with the first symptoms suspicious of MS as substantial treatment consequences will arise.