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

Optimization of Radiofrequency Needle Placement in Percutaneous Cordotomy Using Electromyography in the Deeply Sedated Patient

BACKGROUND AND OBJECTIVES

Cordotomy, the selective disconnection of the nociceptive fibers in the spinothalamic tract, is used to provide pain palliation to oncological patients suffering from intractable cancer-related pain. Cordotomies are commonly performed using a cervical (C1-2) percutaneous approach under imaging guidance and require patients' cooperation to functionally localize the spinothalamic tract. This can be challenging in patients suffering from extreme pain. It has recently been demonstrated that intraoperative neurophysiology monitoring by electromyography may aid in safe lesion positioning. The aim of this study was to evaluate the role of compound muscle action potential (CMAP) in deeply sedated patients undergoing percutaneous cervical cordotomy (PCC).

METHODS

A retrospective analysis was conducted of all patients who underwent percutaneous cordotomy while deeply sedated between January 2019 and November 2022 in 2 academic centers. The operative report, neuromonitoring logs, and clinical medical records were evaluated.

RESULTS

Eleven patients underwent PCC under deep sedation. In all patients, the final motor assessment prior to ablation was done using the electrophysiological criterion alone. The median threshold for evoking CMAP activity at the lesion site was 0.9 V ranging between 0.5 and 1.5 V (average 1 V ± 0.34 V SD). An immediate, substantial decrease in pain was observed in 9 patients. The median pain scores (Numeric Rating Scale) decreased from 10 preoperatively (range 8-10) to a median 0 (range 0-10) immediately after surgery. None of our patients developed motor deficits.

CONCLUSION

CMAP-guided PCC may be feasible in deeply sedated patients without added risk to postoperative motor function. This technique should be considered in a group of patients who are not able to undergo awake PCC.

Open Thoracic Cordotomy for Cancer Pain with Intraoperative Neuromonitoring: A Case Series and Critical Review of the Literature

OBJECTIVE

Cordotomy is a viable option for patients with intractable cancer pain and limited survival. Open thoracic cordotomy is offered when patients are not candidates for percutaneous cordotomy. After the open procedure, traditionally performed purely based on anatomic landmarks, up to 22% of patients experience postoperative limb weakness. The objective of this study is to report our experience with neurophysiology-guided open cordotomy along with a critical review of the literature.

METHODS

Between 2019 and 2022, 5 open thoracic cordotomies were performed in our center. Intraoperative neurophysiologic monitoring was used in all cases to guide the lesion and standard single-level laminectomy or hemilaminectomy was performed for exposure. Outcome measures were retrospectively reviewed focusing on pain control and neurologic status. Existing literature on cordotomy was critically reviewed.

RESULTS

There was satisfactory pain relief with preservation of motor function in all 5 cases. Temperature sensation was preserved in all but 1 patient, who lost it after the previous ipsilateral percutaneous cordotomy (PCC). No procedural complications were experienced. We found that the neurophysiology monitoring lesion was guided anterior compared with what would have been lesioned on an anatomic basis.

CONCLUSIONS

Open thoracic cordotomy is a safe and effective procedure for intractable cancer-related pain. Technical advancements significantly reduced mortality and major morbidity of PCC. Our series suggests that neurophysiology monitoring alters the location of the lesion and may help better targeting of pain fibers within the spinothalamic tract and preserve other long tracts. The safety profile of open cordotomy with neurophysiology compares favorably with the PCC.

Case report: MR-guided laser induced thermal therapy for palliative cingulotomy

In end-stage cancer, oncologic pain refractory to medical management significantly reduces patients' quality of life. In recent years, ablative surgery has seen a resurgence in treating diffuse and focal cancer pain in terminal patients. The anterior cingulate gyrus has been a key focus as it plays a role in the cognitive and emotional processing of pain. While radiofrequency ablation of the dorsal anterior cingulate is well described for treating cancer pain, MRI-guided laser-induced thermal therapy (LITT) is novel. Our paper describes a patient treated with an MRI-guided LITT therapy of the anterior cingulate gyrus for intractable debilitating pain secondary to terminal metastatic cancer.

Dorsal root entry zone procedure and other surgeries for pain

Pain is a very common symptom that often serves a protective function. It is typically treated medically. When pain becomes chronic and intractable, it no longer serves a protective function and often requires more aggressive forms of treatment. Many types of surgeries can be performed for the management of pain. These surgeries can involve ablation (destruction) or augmentation (stimulation or facilitation) of some part of the nervous system. In many of these surgeries, neurophysiologic intraoperative monitoring (NIOM) is not needed, however, in others neuromonitoring serves a mapping and monitoring purpose. The prototype of pain surgery for this chapter is the dorsal root entry zone (DREZ) procedure. Both mapping and monitoring can help improve lesioning precision and outcomes in this surgery. In this chapter, the DREZ procedures and other surgeries for primarily pain relief in which NIOM is used are discussed. Surgeries, such as spinal stenosis, in which pain relief is important but not the sole purpose, are not discussed here and are covered elsewhere.