Stepwise intensity adjustment reduces false positives in transcranial motor evoked potential monitoring during pediatric spine surgery.

OBJECTIVE

Transcranial motor evoked potential (TcMEP) monitoring during pediatric spinal deformity surgery has high false-positive (FP) rates. We evaluated whether a Stepwise Adjustment Technique (SAT) improves diagnostic performance compared with a fixed-intensity (FI) protocol.

METHODS

We retrospectively reviewed 881 pediatric patients (FI, n = 402; SAT, n = 479). In the SAT protocol, when TcMEP amplitude decreased by ≥ 80%, stimulation intensity was increased stepwise up to 200 mA to assess waveform recovery. Diagnostic performance and alert outcomes were compared.

RESULTS

Initial TcMEP decreases were similar between groups (FI, 27.1% vs. SAT, 27.3%). In the SAT group, 61.8% (81/131) of decreases resolved after intensity adjustment and were not adjudicated as TcMEP alerts. For the final amplitude ratio at closure, SAT showed higher specificity than FI (0.97 vs. 0.74) while maintaining high sensitivity. Interrupted time-series analysis showed an immediate improvement in the final ratio after SAT implementation (+11.41%, p = 0.002).

CONCLUSIONS

In pediatric spine surgery, SAT improved TcMEP specificity by reducing false-positive alerts without compromising sensitivity. Although this approach may be particularly useful in spine surgery, caution is warranted where stimulation-threshold elevation is considered an important warning sign.

SIGNIFICANCE: SAT provides a practical framework for repeated TcMEP assessment during spine surgery.