The Utility of Transcranial Electrical Stimulation Motor Evoked Potential Monitoring in Predicting Post-operative Supplementary Motor Area Syndrome and Motor Function Recovery.

OBJECTIVE: Postoperative hemiparesis following frontal lobe lesion resection is alarming, and predicting motor function recovery is challenging. Supplementary motor area (SMA) syndrome following resection of frontal lobe lesions is often indistinguishable from post-operative motor deficit due to surgical injury of motor tracts. We aim to describe the use of intra-operative TES (transcranial-electrical stimulation) with MEP (motor evoked potential) monitoring data as a diagnostic tool in distinguishing between SMA syndrome and permanent motor deficit (PMD).

METHODS: A retrospective analysis of 235 patients undergoing craniotomy and resection with TES-MEP monitoring for a frontal lobe lesion was performed. Patients that developed immediate post-operative motor deficit were included in analysis. Motor deficit and TES-MEP findings were categorized by muscle group as left upper extremity (LUE), left lower extremity (LLE), right upper extremity (RUE), or right lower extremity (RLE). Statistical analysis was performed to determine the predictive value of stable TES-MEP for SMA syndrome versus PMD.

RESULTS: Twenty patients comprising 29 cases of immediate post-operative motor deficit by muscle group were included. Of these, 27 cases resolved and were diagnosed as SMA syndrome while two cases progressed to PMD. TES-MEP stability was significantly associated with diagnosis of SMA syndrome (p=.015). TES-MEP showed excellent diagnostic utility with a sensitivity and positive-predictive value of 100% and 92.6% respectively. Negative predictive value was 100%.

CONCLUSIONS: Temporary SMA syndrome versus PMD is difficult to distinguish immediately postoperatively. TES-MEP may be a useful intra-operative adjunct that may aid in distinguishing SMA syndrome from PMD secondary to surgical injury.