Introduction: We evaluated the usefulness of routine monitoring of transcranial motor evoked potentials(MEP) and its correlation to post-operative neurological outcome in aneurysm surgery, and correlated and compared these data to monitoring of somatosensory evoked potentials(SSEP).
Methods: Between 2010 to 2013, 217 patients underwent surgery for brain aneurysms in two institutions. Patients with no monitoring or only monitoring of one modality were excluded, leaving 201 patients for analyses. Transcranial MEPs and SSEPs were evaluated at induction, during, and at the completion of craniotomy. A greater than 50% decrease in the amplitude of each modality was considered alarming and was communicated to the surgeon. Positive intra-operative findings were correlated with post-operative neurological deficit and CT findings.
Results: Among the 201 patients with brain aneurysms, 133 had SAH. Sixteen patients had MEP changes during surgery, 5 of which improved to baseline after corrective measures were undertaken. In total, 12 patients(6%) has post-operative deficits. Post-operative CT scans at 72 hours confirmed abnormal relevant findings in all 12 patients. 72% of patients with persistent MEP changes at the end of the surgery and one with temporary change(81% of patients with MEP changes) had immediate new post-operative neurological deficits. Three patients with baseline MEPs(1.5% of patients with no MEP changes) had new post-operative deficit. When correlated to SSEP findings, the sensitivity and specificity of MEP with regards to postoperative new deficit were 75% and 98% respectively, as compared to 56% and 99% for SSEP.
Conclusions: There is a significant difference in the predictive value of post-operative new neurological deficit when comparing MEPs and SSEPs. While SSEP monitoring should remain as an important adjunct during aneurysm surgery, monitoring of MEP should be considered as the most reliable indicator of post-operative deficit. Surgical adjustments and corrections can reverse the MEP changes intra-operatively and lead to satisfactory outcomes.
Patient Care: By better understanding of the role of MEP in aneurysm surgery. We think MEP add more to monitor, and help pick up changes faster, so corrective measure can be done, in order to avoid complications
Learning Objectives: To understand the usefulness of routine monitoring of transcranial MEP and SSEP, and the diffrince between them