Introduction: Somatosensory-evoked-potential (SSEP) monitoring has been widely used in cranial and spine surgery to recognize potential damage to the nervous system and monitor the effects of surgical manipulation and anesthesia. This study analyzes the sensitivity and specificity of SSEP monitoring in predicting postoperative neurological deficit in 190 consecutive patients treated surgically for unruptured intracranial aneurysms.
Methods: This is a retrospective analysis of 190 consecutive patients with unruptured aneurysms treated surgically at Oregon Health & Sciences University from 2008 to 2013. Patient charts were reviewed for immediate and 1 week postoperative neurological examinations and operative documentation of SSEP findings.
Results: Of the 190 (175 anterior; 15 posterior circulation aneurysm) that underwent surgery 173 had normal SSEPs throughout the procedure. Two patients (1%) had absent SSEPs prior to surgery, and 1 (1%) had abnormal SSEPs at the start of the surgery. 14 patients (6 posterior; 8 anterior circulation) had SSEP changes during the procedure. One-half (7/14) of SSEP changes during surgery returned to normal prior to closure. A total of 10/190 (11%) of patients had focal neurological deficits postoperatively. In patients with new postoperative focal neurological deficits, 2 did not have intraoperative changes in SSEPs. The remaining 5/7 patients had persistent SSEP changes (4 posterior; 1 anterior) during surgery. Of the 7 patients with abnormal SSEPs at the end of surgery, 2 did not have new focal deficits. The overall accuracy of SSEP changes for predicting new postoperative neurological deficit is 97.9%. The sensitivity and PPV of SSEP changes for predicting postoperative deficit is 71.4%; the specificity and NPV of changes is 98.9%.
Conclusions: Intraoperative SSEP changes are reliable in predicting neurological outcome in unruptured aneurysm surgery. Permanent changes occurred more often in the posterior circulation surgeries. The use of SSEP monitoring in elective aneurysm surgery can help prevent poor neurological outcomes.
Patient Care: The findings of this research suggest that SSEP neuromonitoring can help identify and reverse possible neurological deficits during elective aneurysm surgery. This study highlights the utility of SSEP monitoring and the possible need for additional neuromonitoring during aneurysm surgery.
Learning Objectives: By the conclusion of this session, participants should be able to 1) describe the role of SSEP monitoring in aneurysm surgery, 2) discuss the location of aneurysm and its effects on neuromonitoring, and 3) identify ways to improve monitoring during aneurysm surgeries.