Thrombosed giant aneurysm of the pericallosal artery with inconclusive findings of multiple neuroimaging studies.

A 65-year-old woman presented with a thrombosed giant pericallosal artery aneurysm manifesting as headache and memory loss that developed over a 2-year period. Computed tomography (CT), magnetic resonance (MR) imaging, and conventional and CT angiography could not establish the differential diagnosis. Open craniotomy revealed the mass as thrombosed giant aneurysm from the pericallosal artery. Direct clipping with thrombectomy was performed successfully with an uneventful postoperative course. Thrombosed giant aneurysm of the distal anterior cerebral artery should be considered in the differential diagnosis of an unusual mass in the mid-frontal area, particularly in the presence of inconclusive angiographic and MR imaging findings.