Intraoperative SEP monitoring in aneurysm surgery

Somatosensory evoked potentials (SEP) were monitored during surgical treatment of 282 aneurysms in 226 patients. Significant SEP changes were found in 32 aneurysms (11.3%) mainly referring to accidental or intentional vessel occlusion. Response to these changes included reapplication of aneurysm clips, repositioning of retractors, or removal of temporary clips as followed in 23 cases (8.1%). Stable SEP signals allowed the surgeon to proceed with the surgical course and coincided in all but 2 cases (0.7%) with an uneventful outcome. 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, giant aneurysms, trapping procedures, and procedures requiring temporary vessel occlusion.