D-Wave, and Not SEP or MEP, Is the Best Electrophysiological Predictor of Postoperative Deficit after Surgery for Spinal Cord Tumors

Introduction: Surgery for intraspinal tumors represent a challenging situation, where the chances of new sensorimotor déficits are considerably high. Electrophysiological monitoring might contribute to surgery security, nevertheless, its efficacy, especially the best modality to predict unfavorable outcome, is still a matter of intense controversy. Therefore, we asked whether sensory-, motor evoked potentials (SEP and MEP), and D-waves are efficacious in predicting neurological morbidity.

Methods: We investigated retrospectively 107 patients submitted to surgical treatment of intraspinal tumors at the University of Tübingen under electrophysiological assessment of MEPs, SEPs and wave D. The occurrence of new neurological deficit in the immediate follow-up (prior to hospital discharge) was considered primary outcome, and it was correlated to latency and amplitude changes of the potentials at the end of surgery, compared with the baseline. Data were analysed by means of logistic regression, using JMP 14.0 (SAS Institute, CA).

Results: 20 patients out of 107 presented motor deterioration in the immediate FU, and 12 sensory deterioration. SEP and MEP amplitudes and latencies varied drastically, so that the prediction value of neurologic deterioration was compromised. By contrast, D-waves amplitudes and latencies predicted motor deficits with significant accuracy (logistic whole model test p < 0.05 for both); D-wave amplitude changes predicted sensory changes with less statistical significance (p < 0.10), and latency changes did not (p = 0.34).

Conclusion: D-waves are more reliable in the prediction of new neurologic deficits immediate postoperatively, especially regarding motricity. SEPs and MEPs variability in practical conditions render these methods unreliable.