To describe a rare case of HSV-1–associated CNS vasculitis presenting with multifocal infarcts in a young adult.

HSV-1 is the leading cause of herpetic encephalitis but rarely causes CNS vasculitis. When it occurs, it can lead to ischemic injury, mimicking other inflammatory or vascular disorders. Early recognition is essential for appropriate management.

Single-patient case report with review of clinical, radiologic, and laboratory findings including vessel wall MRI and CSF analysis.

A 22-year-old woman presented with fever, headache, altered mental status, and aphasia. Brain CT showed left temporal hypodensity; CSF PCR confirmed HSV-1. MRI revealed diffusion restriction in bilateral frontal lobes, insular cortex, and left ACA territory. Vessel wall MRI demonstrated circumferential enhancement suggestive of vasculitis. She was treated with intravenous acyclovir for three weeks and corticosteroids with taper. Follow-up MRI/MRA showed temporal atrophy and resolution of vascular abnormalities.

HSV-1 encephalitis complicated by CNS vasculitis is rare and diagnostically challenging. Vessel wall MRI can aid in identifying vasculitic involvement and guide management. Further research is needed to clarify pathogenesis and optimize treatment strategies.