We report 2 cases with giant/large thrombosed aneurysm. One patient, who presented with subarachnoid hemorrhage, had a giant thrombosed aneurysm of the middle cerebral artery and underwent surgery. To prepare for the parent artery occlusion, a STA-MCA bypass was set and motor evoked potential (MEP) was monitored. The aneurysm was cut open, the thrombus was removed, and clipping was performed. Another patient, who presented with visual disturbance, had a large thrombosed aneurysm of anterior communicating artery, which occupied the tubercullum sellae. The aneurysm was clipped after removal of the thrombus.
Since the wall of a thrombosed aneurysm is too hard to clip, the thrombus must be removed before clipping. To prevent premature rupture, a thrombus should be carefully removed, paying attention to the nature of the thrombus.
In preparation for parent artery occlusion, installation of bypass and MEP monitoring is effective. Even after setting a bypass, the blood flow to the perforating arteries should be carefully monitored with MEP.