D waves during spinal cord tumor surgery

D waves can be the most challenging technique in IONM during intradural intramedullary spinal cord tumor surgery. This is compounded by the fact that it is difficult to gain a lot of experience with this technique for most in the field of IONM. While most everyone is comfortable with MEP monitoring, I know very few people in the field who are comfortable with D wave monitoring.

Here is a great blog post that covers all aspects of the technique. https://intraoperativeneuromonitoring.com/d-wave-dorsal-column-mapping/

Here is a great review article by that is open-access (i.e., publicly available) https://www.sciencedirect.com/science/article/pii/S2590139722000242?via%3Dihub#fig1

For establishing baselines and interpreting responses, the blog post and review article highlight two critical factors for performing D waves in my opinion: 1) Appreciation of latency and 2) rostral control.

A D wave can be small response and can be confused with artifact or noise. It’s important to make sure the latency of the response makes sense. Is it too early? Is it too late?

Also, the rostral control electrode provides an invaluable amount of confidence in clinical decision making of baselines and changes from baseline. Is the rostral and caudal response both coming in at the exact same time? That’s a red flag.

When you can’t practice, practice, practice…prepare, prepare, prepare.


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