Unilateral moyamoya disease in a non-Asian patient: a case report with insights on the importance of follow-up

Moyamoya disease is a chronic, progressive occlusive cerebrovascular disorder that can lead to permanent neurological deficits. While typically bilateral and more prevalent in East Asian populations, it can present unilaterally, and cases are increasingly recognized worldwide. The recent 2021 diagnostic criteria now include unilateral disease, emphasizing the importance of early detection and longitudinal follow-up, given the reported 10–39% risk of progression to bilateral involvement. We present a case of unilateral moyamoya disease in a patient of Caucasian descent where the diagnosis was challenging due to the disease’s rarity in this population and the patient’s intermittent, self-resolving neurological symptoms. A 33-year-old Caucasian female patient presented with recurrent episodes of self-resolving headaches and transient hemisensory deficits. Differential diagnoses including transient ischemic attack, migraine with aura, and multiple sclerosis were considered. A stroke protocol was activated on presentation. Computed tomography angiography of the head and neck revealed occlusion of the right distal supraclinoid internal carotid artery with multiple collateral vessels, and cerebral angiography confirmed unilateral right-sided moyamoya disease. The patient was treated with aspirin for antiplatelet therapy to reduce the risk of ischemic stroke and intravenous hydration, with complete symptom resolution. She was counseled on the natural history of the disease, the potential for bilateral progression, and the need for close neurosurgical follow-up. Although moyamoya disease is more common in Asian populations, clinicians must maintain a high index of suspicion in non-Asian patients presenting with recurrent stroke-like symptoms. Early diagnosis with vascular imaging and structured long-term surveillance are essential to prevent neurological complications and to monitor for disease progression or contralateral vascular involvement.