Intraoperative Neurophysiology for Optimization of Percutaneous Spinothalamic Cordotomy for Intractable Cancer Pain

Percutaneous ablation of the cervical spinothalamic tract (STT) remains a therapeutic remedy for intractable cancer pain. However, it is accompanied by the risk of collateral damage to essential spinal cord circuitry, including the corticospinal tract (CST). Recent studies describe threshold-based mapping of the CST with the objective of motor bundle preservation during intramedullary spinal cord and supratentorial surgery.

To assess the possibility that application of spinal cord mapping using intraoperative neuromonitoring in percutaneous cordotomy procedures may aid in minimizing iatrogenic motor tract injury.

We retrospectively reviewed the files of 11 patients who underwent percutaneous cervical cordotomy for intractable oncological pain. We performed quantitative electromyogram (EMG) recordings to stimulation of the ablation needle prior to the STT-ablative stage. We compared evoked motor and sensory electrical thresholds, and the electrical span between them as a reliable method to confirm safe electrode location inside the STT.

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.

Selective STT ablation is an effective procedure for treating intractable pain. It can be aided by quantitative evoked EMG recordings, with tailored parameters and thresholds.