Preliminary study on safe thresholds for temporary internal carotid artery occlusion in aneurysm surgery based on motor-evoked potential monitoring

Abstract

Background: The study aims were to clarify safe duration for temporary vessel occlusion of the internal carotid artery (ICA) during aneurysm surgery as exactly as possible. We examined safe time duration (STD), where brain tissue exposed to ischemia will never fall into even the ischemic penumbra using intraoperative motor-evoked potential (MEP).

Methods: In 45 patients, temporary occlusion of the ICA was performed with MEP. We measured STD as the duration of temporary vessel occlusion during which MEP changes did not occur. To estimate average STD, we calculated the 95% confidence interval for the population mean from sample data for STD in patients with MEP changes and in patients without changes.

Results: In the proximal-control group, 4 of 38 patients (10.5%) developed intraoperative MEP changes. In 4 patients, the time to MEP change (i.e. STD) was 6.0 ± 2.5 min. STD was 3.8 ± 1.6 min in the 34 patients without changes. The average STD was 4.0 ± 0.6 min. In the trap group (proximal and distal flow control), five of seven patients (60.0%) experienced intraoperative MEP changes (STD, 2.3 ± 1.0 min). All patients in the trap group who developed MEP changes showed involvement of the anterior choroidal artery (AchA) in the trapped segment. Average STD was 2.3 ± 1.1 min when trapping involving the AchA.

Conclusions: Although the study is preliminary based on the limited number of the patients, the 95% upper confidence limit for average STD was 4.6 min when the ICA was occluded proximal to the aneurysm, 3.4 min when the ICA was trapped involving the AchA.

Keywords: Aneurysm surgery; internal carotid artery trapping; motor-evoked potential; temporary vessel occlusion.

Figure 1

The histogram demonstrates safe time duration (STD) for temporary vessel occlusion in the proximal-occlusion group. The shaded column demonstrates average STD, representing the 95% confidence interval for the population mean calculated from sample data for STD in patients with motor-evoked potential (MEP) changes and STD in patients without changes. ⋆: MEP changes. Receiver-operating characteristic analysis for detecting MEP changes in proximal group

Figure 2

The histogram demonstrates safe time duration (STD) for temporary vessel occlusion in the trap group. The shaded column demonstrates average STD, representing the 95% confidence interval for the population mean calculated from sample data for STD in patients with motor-evoked potential (MEP) changes and STD in patients without changes. All patients in the trap group who developed MEP changes showed involvement of the anterior choroidal artery in the trapped segment. ⋆: MEP changes