23. Are persistent changes in SEPs and MEPs sensitive for predicting postoperative limb motor deficit during cerebral aneurysm surgery?

Abstract

Introduction Motor evoked potentials (MEPs) can be used as an adjunct to somatosensory evoked potentials (SEPs) to identify brain ischemia during surgical treatment of cerebral aneurysms. Persistent changes (failure to return to baseline by end of surgery) can be used to predict postoperative deficit. The sensitivity, specificity, positive and negative predictive value of persistent changes in SEPs/MEPs for predicting neurologic deficit is still being defined. In a separate study, the sensitivity of persistent changes in SEPs for predicting new limb paresis was 13%, and MEPs was 32%. In this study we evaluated those patients with new postoperative motor deficits to determine the reason for the low sensitivity. Material and methods This was a retrospective study based on 446 cerebral aneurysm patients who underwent clipping at our institution from 2009–2011. Twenty-eight patients with new postoperative motor deficits were identified. The neuromonitoring reports and medical records were reviewed in more detail in these patients. Results In the 28 patients, ten patients (36%, sensitivity) were predicted by persistent SEPs/MEPs changes. In the 18 patients whose deficits were not predicted, five patients (18%) had delayed deficits; eight (29%) had mild temporary motor deficits; in two patients (7%), monitoring was stopped less than ten minutes after aneurysms were clipped; in one patient (3.6%), no reliable SEPs were recorded on the surgery side at baseline. If the last three cases are eliminated, the sensitivity of predicting for all deficit at time when patient wake up is 50% (10/20 patients); to severe and persistent motor deficit is 83% (10/12 patients). Conclusion This study demonstrates that the reason for the low sensitivity of SEPs/MEPs is that these methods are not sensitive to delayed and/or mild temporary deficits. However, the study also shows that SEPs/MEPs have better predictability in cases of severe and persistent postoperative limb paresis.