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What are neuroablative procedures and some pain-associated conditions that are treated by neuroablative procedures?
Neuroablative procedures are destructive procedures that are used to interrupt the transmission of pathological pain pathways. Pain-associated conditions that can be treated with neuroablative procedures include cancer pain, trigeminal neuralgia, and spasticity. Given the permanency of these procedures in contrast to medication or stimulation procedures, patient selection is critical.
What are some types of neuroablative procedures for cancer pain?
- • Anterolateral cordotomy —This procedure focuses on lesioning the lateral spinothalamic tract in the anterolateral part of the spinal cord. It is ideally suited for a patient with unilateral cancer-related nociceptive pain involving a dermatome lower than C5. Bilateral high cervical cordotomies risk inducing Ondine’s curse, which is characterized by suppression of the spontaneous respiratory drive. Neuropathic pain may be more difficult to treat with cordotomy. Techniques include open, fluoroscopic guided, and CT-guided percutaneous approaches.
- • Dorsal root entry zone (DREZ) lesioning —DREZ lesioning involves ablating hyperactive neurons in the dorsal horn of the spinal cord and the excitatory portion of Lissauer’s tract. Ideal patients have segmental pain associated with lesions in the nerve, root, or spinal cord, and the most successful results have been in treating brachial plexus avulsions, where it has been shown to provide relief in over 75% of patients. Techniques for inducing the lesion include microsurgical, radiofrequency, ultrasound, or laser.
- • Myelotomy —This procedure interrupts the ascending posterior visceral pain pathway. It is ideally suited for patients with midline abdominal or pelvic pain, and may be performed using an open surgical technique or percutaneously. A commissural myelotomy which interrupts the crossing fibers of the spinothalamic tract may be useful for bilateral leg pain or sacral pain.
- • Cingulotomy —Lesioning of the cingulate gyrus has been used in the treatment of pain as well as psychiatric disorders. The exact mechanisms for pain reductions are unknown, but ideal candidates have multiples sites of pain secondary to widely metastatic disease. This procedure can be performed using either stereotactic radiofrequency thermocoagulation or laser interstitial thermal therapy.
What are some types of ablative procedures for trigeminal neuralgia and their associated complications?
- • Glycerol rhizotomy —This procedure involves injection of glycerol into the trigeminal cistern. The volume injected is determined by the division of the nerve that is to be affected. Possible complications for all of the percutaneous procedures include damage to the surrounding structures, in particular the surrounding cranial nerves or carotid artery.
- • Percutaneous balloon compression (PBC) rhizotomy —PBC is a procedure that involves inflation of a radiopaque balloon under fluoroscopic guidance in the proximal region of the trigeminal fossa. Unlike other ablative procedures, it can be performed under general anesthesia. Due to a trigeminal depressor response, patients may become acutely and severely bradycardic during balloon inflation. Though a useful marker of an adequate compression, the anesthesia team must be prepared to treat this bradycardia.
- • Radiofrequency (RF) rhizotomy —RF rhizotomy involves thermocoagulation of the trigeminal ganglion. Patients are awake and stimulation of the segments of the ganglion is done prior to ablation to ensure selective ablation of the target trigeminal divisions. Possible complications of this procedure include corneal numbness, keratitis, anesthesia dolorosa, and dysthesias.
- • Stereotactic radiosurgery (SRS) —SRS can be used to target the trigeminal ganglion. Complications are similar to the percutaneous procedures and include sensory dysfunction, and a very low risk of anesthesia dolorosa.
