Somatosensory evoked potentials in the assessment of cerebral ischemia in combined operations for intracranial aneurysms

: Combined surgery of extra-intracranial anastomosis (EICA) and occlusion of the afferent vessel by means of a balloon catheter was made in 14 patients with giant aneurysms of the internal carotid (IC) and middle meningeal artery (MMA). MMA was excluded without previously creating EICA in another patient. The purpose of the study was to define the informative value of a somatosensory evoked potential (SSEP) as an intraoperative criteria for possible permanent occlusion of the major vessel. In 9 patients, IC or MMA occlusion was shown to cause neither intraoperative SSEP changes no postoperative neurological defect. After IC occlusion one case showed 25% reductions in the SSEP amplitude, which was not followed by neurological deterioration. In another patient with IC occlusion, 40% decreases in the cortical response amplitude resulted in moderate postoperative hemiparesis. In one patient with transient IC occlusion, 50% falls in the SSEP amplitude were accompanied by poor EICA function, which made permanent IC occlusion be avoided. However, postoperative neurological defect progression was detected in 3 patients without intraoperative SSEP changes. The findings suggest that SSEP may be used to determine whether IC and MMA can be excluded at surgery for aneurysms. However, no intraoperative SSEP changes does not predict the constancy of a patient's neurological status.