DREZ lesioning, midline myelotomy and chemical neurolytic agents

DREZ lesioning treats deafferentation pain after root avulsion, punctate midline myelotomy targets refractory visceral pelvic and abdominal cancer pain, and alcohol and phenol differ in injection sensation, spread and intrathecal positioning.

1. DREZ targets the dorsal horn generator. After avulsion, hyperexcitable dorsal horn neurons generate pain; lesioning disrupts the central dorsal rootlets, medial Lissauer tract and dorsal horn neurons ¹.
2. Avulsion pain responds durably. In 52 patients followed at least 10 years, mean pain fell from 8.6 to 2.4; 71.2% had complete relief initially and 53.8% at final follow-up ¹.
3. Midline myelotomy interrupts a visceral pathway. A midline dorsal column pathway may matter more than the spinothalamic tract for visceral nociception; punctate myelotomy has relieved intractable abdominal and pelvic cancer pain ².
4. Myelotomy relieved pain without deficits. In six patients with refractory visceral cancer pain, pain ratings and daily opioid use fell significantly without adverse neurological effects ³.
5. Alcohol burns and spreads. Ethyl alcohol (at least 35–60%) causes burning on injection and spreads rapidly, so larger volumes are often needed; intrathecally the patient is tilted forward 45 degrees ⁴.
6. Phenol is gentler and stays local. Phenol has local anesthetic properties and a warming sensation, spreads little in glycerin, and is injected intrathecally with the patient tilted backward 45 degrees ⁴.

Chemical neurolysis is nonselective: off-target tissue damage, skin sloughing, post-procedure neuritis and, near the celiac plexus, vascular injury make it a therapy of last resort ⁴.

• DREZ complications in the 10-year series were mainly mild proprioceptive disturbance (9 of 52), with motor weakness in one patient ¹.
• Brachial plexus avulsion combined with cervical spinal cord injury correlated with poorer DREZ outcomes ¹.
• DREZ lesions in the series were about 3–4 mm deep, angled roughly 35 degrees, targeting hyperactive dorsal horn neurons ¹.
• Myelotomy was proposed when opioids cannot control cancer pain or their side effects are intolerable ³.
• Phenol concentrations for neurolysis are thought to range from 3% to 12%; it acts immediately and can be repeated within days ⁴.
• Alcohol neurolysis is routinely used for visceral cancer pain or for pain recurring after radiofrequency ablation ⁴.
• Phenol must be prepared by the hospital pharmacy, and it is unstable at room temperature and oxidizes in air and light ⁴.

• Choosing dorsal root ganglion removal for avulsion pain, whose generator lies in the dorsal horn ¹.
• Choosing cordotomy for visceral pelvic pain that travels in the midline dorsal column pathway ².
• Using the same intrathecal position for alcohol and phenol ⁴.