Foix-Chavany-Marie syndrome: A rare presentation with arachnoid cyst involvement.

Foix-Chavany-Marie syndrome, also known as opercular syndrome, is a rare neurological condition typically caused by bilateral lesions of the opercular cortex. Involvement of arachnoid cysts in the pathogenesis is extremely uncommon. We report the case of a 66-year-old male who presented with sudden-onset dysarthria, dysphagia, and bilateral lower facial paralysis, but retained the ability to yawn and smile, demonstrating the characteristic dissociation between voluntary and involuntary orofacial movements. Magnetic resonance imaging revealed an acute infarction in the left corona radiata and a right-sided arachnoid cyst, leading to a diagnosis of Foix-Chavany-Marie syndrome. This case highlights a classic presentation of Foix-Chavany-Marie syndrome with a potentially novel pathogenic contribution from an arachnoid cyst.