Intraoperative test occlusion as adjustment of extracranial-to-intracranial bypass strategy for unclippable giant aneurysm of the internal carotid artery

Background There is still a controversy for low-flow extracranial–intracranial or high-flow extracranial–intracranial bypass with proximal occlusion in the treatment of unclippable giant internal carotid artery aneurysms. Case Description A 61-year-old woman presented with a 1-month history of double vision. Neuroimages revealed an unclippable giant internal carotid artery aneurysm located from the cavernous sinus to proximal site of the posterior communicating artery. Ipsilateral A1 of the anterior cerebral artery was hypoplastic, and posterior communicating artery was patent. Intraoperative proximal test occlusion at cervical internal carotid artery under neurophysiological monitoring, instead of preoperative balloon test occlusion, was performed to assess whether low-flow bypass was sufficient. The monitoring was unchanged during test occlusion, and the aneurysm was successfully trapped without high-flow bypass. Neither ischemic lesion nor neurologic deficits were found postoperatively. Conclusions Intraoperative proximal test occlusion is useful to decide on the surgical procedure of revascularization in patients with unclippable internal carotid aneurysm.