Transcranial motor evoked potential monitoring outcome in the high-risk brain and spine surgeries: Correlation of clinical and neurophysiological data – An Indian perspective

OBJECTIVE: The objective of this study is to assess the safety, feasibility and clinical value of transcranial motor evoked potential (MEP) monitoring by electrical stimulation. SETTING: Clinical neurophysiology department of tertiary reach hospital. MATERIALS AND METHODS: MEP monitoring was attempted in 44 “high risk” patients. Intraoperative surgical, anesthesia and neurophysiological findings were documented prospectively. MEP monitoring results were correlated with motor outcome. RESULTS: The success for reliable MEP recording from the lower limbs was 75%. Incidence of new permanent post-operative motor deficit was zero. Nearly, 76.5% of the cases (13 out of 17 cases) who showed unobtainable and unstable MEP outcome had lesion location in the spine as compared with 23.5% (4 out of 17 cases) that had lesion location in the brain. Chi-square test demonstrated a statistically significant difference between these two groups (P = 0.0020). Out of these 13 spine surgery cases, 8 (62%) were operated for deformity. Seven out of 12 (60%) patients less than 12 years of age had a poor MEP monitoring outcome suggesting that extremes of age and presence of a spine deformity may be associated with a lesser incidence of successful MEP monitoring. No complications related to the repetitive transcranial electrical stimulation for eliciting MEP were observed. CONCLUSION: MEP monitoring is safe. The protocol used in this study is simple, feasible for use and has a fairly high success rate form the lower limbs. Pediatric age group and spine lesions, particularly deformities have an adverse effect on stable MEP recording.