Intracranial Mycotic Aneurysm in a Patient with Abdominal Actinomycosis.

Actinomycosis of the central nervous system is extremely rare. A 73-year-old woman with a history of abdominal actinomycosis presented with sudden-onset headache. Magnetic resonance imaging demonstrated a nodular lesion at the left precentral gyrus. A cerebral angiogram confirmed a fusiform aneurysm arising from the precentral branch of the left middle cerebral artery. High-resolution vessel wall imaging revealed circumferential wall enhancement of the aneurysm and multifocal enhancement of the M3 and M4 segments of both middle cerebral arteries. The patient had received a 4-week course of antibiotics, but follow-up angiography demonstrated no shrinkage or resolution of the aneurysm. Trapping combined with revascularization was successfully performed for refractory mycotic aneurysms.