Intraoperative Neurophysiological Monitoring in Cerebral Aneurysms Surgery

Introduction The effectiveness of surgical treatment for cerebral aneurysms is due to the improvement of surgical and anesthetic methods that allow for the exclusion of aneurysms from the blood flow. An important condition for the safe isolation and clipping of an aneurysm is the temporary shutdown of blood flow in the artery, in particular, temporary clipping (TC) of the artery carrying the aneurysm. Intraoperative neurophysiological monitoring (IONM) was proposed to predict ischemic complications in the treatment for intracranial aneurysms using TC. However, data on the results of using IONM in clipping cerebral aneurysms are contradictory.

The aim of the study was to evaluate the effectiveness of intraoperative neuromonitoring in the surgical treatment for cerebral aneurysms.

Material and methods The examination and surgical treatment of 93 patients with cerebral aneurysms was performed; patients were divided into 2 groups: Group 1 (no IONM) — 48 patients who underwent open clipping of the aneurysm without the use of intraoperative neuromonitoring (control group); Group 2 (IONM) — 45 patients who underwent IONM during surgical treatment for cerebral aneurysms in the internal carotid artery and middle cerebral artery.

The treatment outcomes were assessed by the indicators of the radicality of exclusion of the aneurysm from the blood flow, functional outcomes - by the Glasgow Outcome Scale and the Rankin scale. During IONM, transcranial electrical stimulation (TES) was performed, with the impulse being delivered through the bones of the skull from electrodes located on the scalp surface, and motor evoked potentials (MEP) were recorded, direct electrical stimulation of the cerebral cortex (DES-MEP) was performed using a strip electrode laid along the precentral gyrus. After isolating the parent vessel, TC was performed in order to dissect the aneurysm from the surrounding tissues.

Results It was found that the use of IONM during blood flow interruption in surgical treatment for cerebral aneurysms was accompanied by a decrease (compared to the group of patients without neuromonitoring) in the number of cases of temporary clipping by 33%, an increase in the total duration of TC by 25%, a decrease in the number of reperfusions by 50%, a decrease in the total duration of reperfusions by 3 times, a decrease in the duration of one ТC session by 10%, and a decrease in the volumetric blood flow through the carrier arteries by 18.1%.

At the same time, no significant intergroup differences in systemic hemodynamic parameters were observed. Also, during IONM, there was no decrease in the amplitude of the MEP-TES in 93.3% of patients, the amplitude of evoked potentials did not change in 77.8–91.2% of patients, while the course of the operation changed in 33.3% of patients. In the early postoperative period, in patients who underwent IONM during TC performance, the proportion of patients with a Glasgow Coma Scale score of 14–15 points was 51% higher, and with a score of 9–13 points 8.8 times lower (than in the group without IONM), speech disorders were detected 2.5 times less often, the presence of cerebral ischemia zones was noted 1.8 times less often.

Conclusion Thanks to the feedback provided by the use of IONM in real time, the surgeon can always immediately respond to the development of structural damage to the brain, which in turn helps prevent neurological disorders during surgical treatment of cerebral aneurysms. The use of IONM during open clipping of aneurysms allows increasing the number of excellent treatment outcomes by 44%.

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