A wide-necked saccular aneurysm of the middle cerebral artery bifurcation with neck atherosclerosis mimicking a fusiform aneurysm: illustrative case.

BACKGROUND

The authors report a rare case of a complex wide-necked saccular middle cerebral artery (MCA) bifurcation aneurysm with atherosclerotic plaque at the neck, which mimicked a fusiform aneurysm.

OBSERVATIONS: A 68-year-old female presented with a 1-month history of dizziness. Angiography showed a fusiform aneurysm arising from the superior division of the left MCA. Contrast-enhanced black-blood MRI demonstrated marked aneurysmal wall and lumen enhancement, absent on noncontrast images. On surgical opening, a wide-necked saccular aneurysm was instead found. A calcified/atheromatous plaque was present at the aneurysm neck, which explained the radiological findings of a fusiform-looking aneurysm. The surgical strategy consisted of complex clip reconstruction with distal revascularization via an extracranial-to-intracranial (EC-IC) bypass.

LESSONS: In this case, preoperative angiography suggested a fusiform MCA aneurysm, but intraoperative examination revealed a wide-necked saccular aneurysm. The presence of atheromatous plaques at the aneurysm neck can distort its angiographic appearance and pose a challenge for clip reconstruction. Performing a preoperative vessel wall MR study may improve characterization of aneurysmal morphology and support tailored management of complex cases. https://thejns.org/doi/10.3171/CASE2684.