Intraoperative monitoring of cerebral cortical blood flow and middle cerebral artery pressure as a substitute for preoperative balloon test occlusion in patients with internal carotid artery aneurysms.

Abstract

Balloon test occlusion (BTO) is a useful examination to evaluate the indications and methods for revascularization when treating unclippable internal carotid artery (ICA) aneurysms by parent artery occlusion. The purpose of the present study was to investigate the relationship between intraoperative monitoring of cerebral cortical blood flow (CoBF) and middle cerebral artery (MCA) pressure during surgical parent artery occlusion and the findings of BTO. Eleven patients with an ICA aneurysm in the cavernous portion underwent preoperative BTO with brain perfusion single-photon emission tomography. CoBF was monitored intraoperatively in all patients using a laser Doppler probe. The lowest CoBF during test occlusion of the ICA under functioning superficial temporal artery-middle cerebral artery (STA-MCA) bypass was determined, and the ratio of the value to the CoBF immediately before test occlusion of the ICA was calculated in the frontal and temporal lobes. When the CoBF ratio in the frontal or temporal lobe was less than 0.9, high-flow bypass grafting was added. The MCA pressure was also measured by temporarily occluding the proximal STA. Of the 11 patients undergoing STA-MCA bypass, 5 patients underwent concomitant high-flow bypass grafting. Significant differences in the cerebrovascular reserve based on SPECT during BTO, CoBF, and the MCA pressure ratio during surgery were observed when comparing the two groups. Intraoperative monitoring of CoBF and MCA pressure may be useful, along with preoperative BTO, for patients with unclippable ICA aneurysms.