Diagnostic value of D-wave and motor evoked potentials in intramedullary spinal cord tumor surgery: a temporal analysis of predictive accuracy.

Authors

Anup Kumar Roy, Madhusudhan Nagesh, Andiperumal Raj Prabhuraj, Kadarapura Nanjundaiah Gopalkrishna, Nupur Pruthi, Manish Beniwal, Abhinith Shashidhar, Nishanth Sadashiva, Arivazhagan Arimappamagan

Published in

Neurosurgical review. Volume 49. Issue 1. Jun 29, 2026. Epub Jun 29, 2026.

Abstract

The surgical resection of intramedullary spinal cord tumors (IMSCTs) is associated with significant morbidity. Intraoperative neuromonitoring (IONM) with transcranial myogenic motor evoked potentials (m-MEP) and D-wave aims to reduce new postoperative motor deficits. Still, their comparative ability to predict short- and long-term outcomes is incompletely defined. We evaluated the diagnostic performance of m-MEP and D-wave monitoring at multiple postoperative time points and examined their influence on intraoperative decision-making.
In this single-institution observational study (2017-2024), we included 44 patients undergoing resection of IMSCTs with multimodal IONM. Neurological status was assessed using Medical Research Council (MRC) grade and Modified McCormick Scale (MMS) preoperatively, immediately (0-3 days), at discharge (7-14 days), and at ≥ 6 months follow-up. Statistical analyses were used to correlate the postoperative deficits with attenuation of m-MEP and D-wave potentials during surgery. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated and compared using McNemar's test.
Mean age was 36.6 ± 15.1 years; mean follow-up was 14.5 ± 7.2 months. IONM attenuation occurred in 20 patients (45.5%): m-MEP drop in 20 (45.5%) and D-wave amplitude reduction in 6 (13.6%); no case had a complete loss of D-wave. Immediate postoperative motor deficits occurred in 72% (MRC) and 38.6% (MMS), declining to 15% and 9% at follow-up, respectively. D-wave attenuation correlated significantly with deficits immediately (p = 0.02) and at discharge (p = 0.027) but not at follow-up (p = 0.257). m-MEPs demonstrated higher sensitivity (51-66%) but lower specificity than D-waves across time points. D-waves showed lower sensitivity (35-75%) but consistently high specificity (95-100%). D-waves demonstrated superior diagnostic accuracy at follow-up compared with m-MEPs (84% vs. 59% on MRC; 93% vs. 64% on MMS; p < 0.001). The PPV of both modalities declined over time, while the NPV and sensitivity improved at the last follow-up. False positives were more common with m-MEPs (30-40%) than with D-waves (0-5%).
The predictive accuracy of IONM varies with time following surgery. m-MEPs are more sensitive for detecting immediate postoperative deficits, while D-waves are more specific and have superior predictive accuracy for long-term motor outcomes. Their complementary roles highlight the importance of multimodal monitoring as a surgical guide rather than a restrictive determinant of resection.
Not applicable.

PMID:
42371199
Bibliographic data and abstract were imported from PubMed on 29 Jun 2026.

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