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

Area of Science:

• Neurosurgery
• Spinal Surgery
• Neurophysiology

Background:

• Transcranial motor evoked potential (TcMEP) monitoring is crucial in pediatric spinal deformity surgery.
• High false-positive rates with fixed-intensity (FI) protocols can lead to unnecessary surgical interventions.

Purpose of the Study:

• To evaluate if a Stepwise Adjustment Technique (SAT) improves the diagnostic performance of TcMEP monitoring compared to a fixed-intensity (FI) protocol.
• To reduce false-positive alerts during pediatric spinal deformity surgery.

Main Methods:

• Retrospective review of 881 pediatric patients undergoing spinal surgery (402 FI, 479 SAT).
• In the SAT protocol, TcMEP stimulation intensity was increased stepwise (up to 200 mA) if amplitude decreased by ≥80% to assess waveform recovery.
• Comparison of diagnostic performance and alert outcomes between FI and SAT protocols.

Main Results:

• Initial TcMEP decreases were similar between groups (FI: 27.1%, SAT: 27.3%).
• In the SAT group, 61.8% of initial decreases resolved with intensity adjustment, avoiding false-positive alerts.
• SAT demonstrated significantly higher specificity (0.97 vs. 0.74) than FI at closure, maintaining high sensitivity. Interrupted time-series analysis showed immediate improvement in the final ratio after SAT implementation (+11.41%, p=0.002).

Conclusions:

• The Stepwise Adjustment Technique (SAT) enhances TcMEP monitoring specificity in pediatric spine surgery by reducing false-positive alerts.
• SAT improves diagnostic accuracy without compromising sensitivity, offering a practical framework for repeated intraoperative assessment.
• Caution is advised in scenarios where stimulation threshold elevation is a critical warning sign.