12/15/2025
Most in neuromonitoring are familiar with monitoring hashtag cases for chronic pain. But what about the more extreme Corodotomies?
Spinal cord ablation is almost exclusively used for refractory cancer pain and in the palliative care setting, whereas neuromodulation remains a more robust long-term treatment for patients with refractory chronic pain.
- Different patient populations.
- Different surgical goals.
- Different monitoring techniques.
Instead of utilizing the pain gate theory for pain relief, the surgical plan here is to target the spinothalamic tract.
At a given spinal level in the spinothalamic tract, axons come from cells located in the contralateral cord 2 to 3 spinal segments lower because the Lissauer tract conducts pain fibers rostrally and ipsilaterally before they crossover to join the spinothalamic tract.
So, pain control with cordotomy is achieved 3 or 4 levels below the level of the lesion.
With this surgery, we're looking to help preserve movement and light touch/temperature sensation through tcMEP and SSEP.
As we see a decrease in conduction, we alert the surgeon. From there, the discussion of a pause to look for recovery, changing approach, or stopping ablation, early-stage post-op therapeutics, etc., are all part of the conversation.
But before we get to that point, we might help better assess the site to be lesioned. By using Quantified EMG data, we might help approximate the distance to specific motor areas.
What might those parameters look like? Here's what was retrospectively looked at by Sapir and Korn:
"Quantified EMG data were collected in 11 patients suffering from intractable cancer pain. The threshold range for evoking motor activity was 0.3 to 1.2 V. Stimulation artifacts were detected from trapezius muscles even at the lowest stimulation intensity, while thenar muscles were found to be maximally sensitive and specific. The minimal stimulation intensity difference between the motor and the sensory threshold, set as “Δ-threshold,” was 0.26 V, with no new motor deficit at 3 days or 1 month postoperatively."
Sapir, Yechiam & Korn, Akiva & Bitan-Talmor, Yifat & Vendrov, Irina & Berger, Assaf & Shofty, Ben & Zegerman, Alexander & Strauss, Ido. (2020). Intraoperative Neurophysiology for Optimization of Percutaneous Spinothalamic Cordotomy for Intractable Cancer Pain. Operative Neurosurgery. 19. 10.1093/ons/opaa209.