Moyamoya Vasculopathy with Atypical Cogan's Syndrome: A Case Report.

Cogan's syndrome (CS) is a rare autoimmune disorder involving audio-vestibular and ocular inflammation. While systemic vasculitis is a known complication, its association with Moyamoya-type cerebrovascular remodeling has not been previously documented. A 19-year-old Asian woman was diagnosed with atypical CS following a presentation of hyperpyrexia, unintentional weight loss, and severe bilateral sensorineural hearing loss. After five years of appropriate immunosuppressive treatment, she developed subacute headaches, hypertension, and left hemiparesis and paresthesia. Despite normal inflammatory markers, neuroimaging revealed right-sided internal carotid artery occlusion and extensive collateralization characteristic of Moyamoya syndrome. Genetic testing showed a variant of uncertain significance in SLC37A4. The patient underwent a right extracranial-intracranial (STA-MCA) bypass, resulting in complete resolution of neurological symptoms. The late emergence of Moyamoya suggests that chronic autoimmune-mediated vascular injury may trigger progressive steno-occlusive disease. Clinicians should consider Moyamoya syndrome as a differential for new neurological symptoms in CS patients, even when systemic inflammation appears controlled. To our knowledge, this is the first reported case of concurrent Cogan's syndrome and Moyamoya vasculopathy at time of writing this article.