Surgical and electrophysiological observations during clipping of 134 aneurysms with evoked potential monitoring

Abstract

Somatosensory evoked potentials (SEPs) were monitored during 113 operations for the clipping of 134 cerebral aneurysms. Changes in peak latency and amplitude of early cortical SEP as well as central conduction time were evaluated. In 58 cases surgical occlusion of arterial vessels or other events occurred, and in 17 of these cases such events were associated with SEP changes or loss. Arterial occlusions resulted from temporary clipping of a feeding blood vessel (22), accidental clipping of a vessel (12), and intentional permanent vessel occlusion (8). A total SEP loss was seen in 2 cases of accidental vessel occlusion and in 6 cases of temporary vessel clipping. Significant SEP changes were found in 6 patients with temporary clipping, and once each with retraction of the cerebellum, retraction of the middle cerebral artery, and after intentional permanent vessel occlusion. Response to these changes included reapplication of aneurysm clips, repositioning of retractors, or removal of temporary clips. Stable SEP signals during 13 cases allowed the surgeon to proceed with the surgical course. Despite the limitations of SEP monitoring in certain anatomical locations, it has been found to be helpful in the operative management of some cases such as multilobed aneurysms of the middle cerebral artery, giant aneurysms, trapping procedures, and procedures requiring temporary vessel occlusion.

Monitoring of motor evoked potentials compared with somatosensory evoked potentials and microvascular Doppler ultrasonography in cerebral aneurysm surgery

“…In all, the combined monitoring in this series resulted in a direct alteration in the surgical course in 33% of cases, and EP monitoring alone led to a procedural change in 20% of cases. These results emphasize the increased efficiency of the multimodal approach compared with data from other series in which SSEP monitoring alone prompted a surgical consequence in 13 35 and 10% 36 of cases. Furthermore, MEP monitoring alone triggered surgical measures in 18.5% of cases 40 compared with 16% of all cases and 20% of those cases involving successful MEP monitoring in the present series.…”

“…In addition, there was only one case of new paresis ascribable to inadvertent occlusion in this series, in contrast to higher rates in the literature. 20,35,36 It is therefore possible that MDU helped to avoid persistent new deficits in some cases, corresponding to pre-vious observations on the positive effect of MDU on outcome following aneurysm surgery. 5,7 …”

“…3,6,8,10,17,19,22,24,25,35,36 Nonetheless, a significant rate of up to 25% of cases with new postoperative neurological deficits (mainly pareses), despite unaltered intraoperative SSEP recordings, has been observed ( Fig. 1).…”

“…13,18,23,26 A multitude of intraoperative conditions or events can be associated with ischemia of eloquent brain regions and postoperatively impaired neurological function, including intentional and inadvertent occlusion of vessels, compromise to small perforating vessels during dissection, and disturbed local microcirculation from brain retraction. 35 In many cases, inspection alone cannot reveal impending ischemia and must be supported by complementary methods better suited for such monitoring purposes.…”

Temporary occlusion of the middle cerebral artery in intracranial aneurysm surgery: time limitation and advantage of brain protection

“…Many authors have reported favorable results obtained by performing routine reversible arterial occlusion with a temporary aneurysm clip as an adjunct to safe aneurysm dissection and following intraoperative rupture. 2,3,6,[11][12][13]20,22,23,[26][27][28][29][30][31][32][33][34][35]37,39,43,47,53,54 These investigators have reported a wide range of safe occlusion time limits based, most commonly, on clinical outcome and have generally evaluated aneurysms in several arterial distributions and generalized the results to all aneurysms. Radiographic evidence of infarction and various intraoperative and perioperative monitoring techniques have been the focus of more recent studies.…”