[Intraoperative somatosensory evoked potentials (SSEP) in surgery of cerebral aneurysms: topographical information]

Out of 114 patients who were operated because of cerebral aneurysms, 16 patients were monitored by means of Somatosensory Evoked Potential (SSEP) during the operation. In 9 of these, successful monitoring was possible during the whole duration of the surgical procedure. In the remaining seven, monitoring was impossible over a long period so that these patients were excluded from the present study. Monitoring of the cerebral functions by means of SSEP provides help in aneurysm surgery as follows: Objective evaluation of the function of the somatosensory system. The induced arterial hypotension--usually done in our department--implies danger for the brain, particularly, if rupture of the aneurysm occurs at the same time. In this case, Somatosensory Evoked Potentials provide the possibility to detect lesions of somatosensory neurons at different levels. This makes prognostic conclusions possible. Pathological changes of some SSEP components during temporary occlusion of arteries of the Circle of Willis indicate developing lesions of brain structures. Intraoperative SSEP data were correlated with the postoperative course in all 9 patients. Prognostic conclusions derived from these data are discussed.