Alarm criteria for motor evoked potentials

To evaluate three commonly used alarm criteria for interpreting the significance and diagnostic value of transcranial motor evoked potential (TcMEP) changes during spinal surgery.

A systematic literature search was performed using PubMed/MEDLINE, Web of Science, and EMBASE from 1945 to January 2014. We included all those studies that were (1) randomized controlled trials, prospective studies, or retrospective cohort studies, (2) conducted among patients undergoing surgery on the spine or spinal cord with TcMEP monitoring, (3) conducted in a group of ≥50 patients, (4) that were inclusive of immediate postoperative neurological assessment (within 24 h), and (5) which were published in English.

Twenty-five studies involving 9409 patients were included. The incidence of neurological deficits was 1.82%. The overall sensitivity and specificity of all reported TcMEP changes was 82.1% (95% confidence interval [CI]: 73-88.6%) and 95.7% (95% CI: 93.7-97.1%), respectively. The sensitivity and specificity of each alarm criteria were evaluated: 50% reduction in amplitude, sensitivity 63.2% (95% CI: 47-76.8%), and specificity 96.7% (95% CI: 96.4-99.2%); 80% reduction in amplitude, sensitivity 71.7% (95% CI; 42-89.9%), and specificity 98.3% (95% CI: 96.4-99.2%); total signal loss, sensitivity 30% (95% CI: 17.6-46.4%), and specificity 99.3% (95% CI: 98.6-99.7%).

No statistically significant differences between using reductions in amplitude of 50% and 80% as alarm criteria were found in terms of sensitivity and specificity. Total loss was found to have a statistically significant increase in specificity. TcMEP monitoring is a highly specific and sensitive diagnostic tool for the detection of neurological defects during spinal surgery.