Neurophysiological monitoring in the endovascular therapy of aneurysms

Abstract

Background and purpose: Endovascular aneurysm therapy has associated risks of ischemic complications. We undertook this study to evaluate the efficacy of neurophysiological monitoring (NPM) techniques in the detection of ischemic changes that may be seen during endovascular treatment of cerebral aneurysms.

Methods: Thirty-five patients underwent NPM during endovascular treatment of cerebral aneurysms. The patients underwent a total of 50 endovascular procedures, including balloon test occlusion (19 patients), GDC embolization (22 patients), and permanent vessel occlusion (nine patients). NPM included electroencephalography, somatosensory evoked potentials, and/or brain stem auditory evoked potentials, depending on the location of the aneurysm.

Results: NPM changes were seen in nine (26%) of 35 patients and altered the management in five (14%) of 35 patients. In three of the five cases, NPM changes were observed without corresponding neurologic physical examination changes after balloon test occlusion (performed while the patients were under general anesthesia in two cases). In the two other cases in which NPM changes altered management, ischemia was detected at the time of intra-aneurysmal therapy while the patients were under general anesthesia. Overall, 18 of 35 patients underwent a total of 19 balloon test occlusion procedures. Of the 17 remaining patients, 13 underwent aneurysm coiling, two were not treated because of inability to safely place coils, and two were treated for distal aneurysms. Two patients developed transient neurologic deficits without concurrent NPM changes, representing false-negative NPM test results.

Conclusion: NPM is a valuable adjunct to endovascular treatment of cerebral aneurysms. Our study suggests that these monitoring techniques may reduce ischemic complications and can be used to help guide therapeutic decisions.

Fig 1.

Images from the case of a 78-year-old woman who presented with symptoms of a subarachnoid hemorrhage. A, Left internal carotid artery injection in the anterolateral projection shows a 5-mm left middle cerebral artery bifurcation aneurysm (arrow). Intra-aneurysmal coiling was attempted while the patient was systemically heparinized. B, Baseline cerebral SSEPs after bilateral median nerve stimulation. Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow). C, One minute after coil placement into the aneurysm, a >50% decrease in amplitude of the right median nerve SSEP was noted (arrow). This is consistent with significant left cerebral ischemia. Fluoroscopic evaluation suggested the coil was partially prolapsed into the parent artery, and considering the change in potentials, it was decided to quickly remove this coil. Formal angiographic assessment may well have shown significant compromise in the parent vessel; however, because the changes were rapid and profound, the coil was removed. Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow). D, Left cerebral evoked potential (arrow) returned to baseline levels after removal of the coil. Because coil embolization could not be performed safely, the patient subsequently underwent surgical clipping of the aneurysm. Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow).

Fig 2.

Images from the case of a 75-year-old woman who presented with a ruptured giant left internal carotid artery aneurysm. A, Lateral projection angiogram of the left internal carotid artery shows the aneurysm arising in the supraclinoid segment shortly after the takeoff of the ophthalmic artery. The aneurysm was thought to be unfavorable for GDC embolization, and balloon test occlusion was thus performed in anticipation of permanent vessel occlusion. Because of the patient’s physical condition, the procedure could be performed only with the patient under general anesthesia. B, Baseline cerebral SSEPs after bilateral median nerve stimulation. Note the baseline asymmetry, with the right median nerve SSEP (arrow) being smaller in amplitude than the left. Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow). C, Left internal carotid artery balloon test occlusion was performed, resulting in gradual amplitude reduction of the left cerebral (right median nerve stimulation) SSEP over 5 min and precipitous decrease in the 6th min. The SSEP obtained 6 min after balloon occlusion shows a nearly complete loss of the left cerebral SSEP (arrow). Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow). D, Balloon was deflated immediately after the SSEP tracing shown in 2C. The cerebral SSEP returned to baseline amplitude levels after 1 min (arrow). Top tracing, left median nerve stimulation (ie, right brain); bottom tracing, right median nerve stimulation (ie, left brain) (arrow).