Focal Cerebral Arteriopathy in a Young Adult.

Focal cerebral arteriopathy (FCA) is a rare, monophasic stenosis of the distal internal carotid artery (ICA) or proximal middle cerebral artery that primarily affects children but is occasionally seen in adults. It is unclear what causes FCA in adults, which complicates diagnosis and management. The case presented highlights diagnostic challenges using multimodal imaging, supporting conservative management, and the need for adult-specific treatment criteria. A 38-year-old woman with a history of breast cancer, migraines, and prior pulmonary embolism presented with a sudden-onset thunderclap headache and expressive aphasia. Initial imaging revealed high-grade left ICA terminus stenosis, with differential diagnoses including reversible cerebral vasoconstriction syndrome and vasculitis. The patient was readmitted two days after her initial presentation for worsening symptoms, including right-sided facial and arm numbness, as well as visual hallucinations. Multimodal imaging, blood work, and lumbar puncture excluded alternative diagnoses. Digital subtraction angiography confirmed 70% left supraclinoid ICA stenosis that was unresponsive to intra-arterial verapamil, ruling out reversible cerebral vasoconstriction syndrome. Serial imaging demonstrated progressive improvement in the stenosis (59% at one month and 46% at six months). The patient has not experienced symptom recurrence and reports being at her neurologic baseline. This case underscores the challenges of diagnosing FCA in young adults because of its overlap with several other arteriopathies, resulting in unnecessary interventions and lifelong misdiagnosis. Multimodal imaging is critical for accurate diagnosis and monitoring. The self-limiting nature of FCA supports conservative management, but adult-specific diagnostic criteria are needed to improve recognition and guide therapy.