Evaluation of post-tetanic motor evoked potential as an augmentation technique under partial neuromuscular blockade during craniotomy

Abstract

Objective

In craniotomies requiring motor evoked potential (MEP) monitoring, avoiding neuromuscular blockade (NMB) is preferable, but its complete avoidance poses risks of unexpected movement. This retrospective study investigates the application of a post-tetanic MEP augmentation technique to enhance baseline recording of transcranial stimulation MEP (Tc-MEP) under partial NMB during craniotomy.

Methods

Twenty-six patients were included. The level of partial NMB was maintained at a train-of-four ratio of approximately 40 %. Monophasic constant-current stimulation was applied on the craniotomy side with + 20 % of the threshold intensity. Post-tetanic Tc-MEP, involving tetanic stimulation of the median nerve 1 s before transcranial stimulation, was performed on patients who failed to record using conventional baseline recording.

Results

The post-tetanic Tc-MEP technique successfully improved the success rate of baseline recording from 61.5 % to 100 %. Application of post-tetanic Tc-MEP significantly increased amplitudes in both the upper (p = 0.04) and lower limbs (p < 0.01) compared to before post-tetanic Tc-MEP. No patients had unexpected movements.

Conclusions

This study indicates that post-tetanic Tc-MEP enhanced the success rate of baseline recording during craniotomy under partial NMB.

Significance

The combination of partial NMB and post-tetanic Tc-MEP could be a useful regimen for craniotomy with MEP monitoring, addressing both safety concerns and successful baseline recording.