Abstract
Increasing evidence implies the existence of a visceral pain pathway in the dorsal column of the spinal cord. Limited midline myelotomy has been used to treat intractable pelvic cancer pain. However, no obvious evidence has been provided that high cervical punctate midline myelotomy (CPMM) relieves visceral pain originating from the abdomen. This study was designed to examine the pain relief effect of CPMM in a mouse model of visceral pain. Thirty-six Institute of Cancer Research (ICR) mice were divided into three groups: Group 1, healthy controls; Group 2, treated with CPMM at C1 and C2; and Group 3, a sham group that underwent laminectomy at C1 and C2 without CPMM. All animals were tested for antinociception in the writhing test 24 hours after surgery. Visceral pain-related behaviors were counted from 5-20 minutes after intraperitoneal injection of 0.6% acetic acid. Writhing test scores were not significantly different between Groups 1 (56.7 +/- 10.7) and 3 (50.7 +/- 17.4). However, Group 2 (30.0 +/- 14.3) showed more than 40% antinociception after treatment, and writhing test scores were significantly different from those of Groups 1 and 3 (p < 0.001). Our results confirm that midline punctate myelotomy can relieve visceral pain and imply that there is a pathway in the posterior funiculus that signals visceral pain. Punctate midline myelotomy at the cervical or high thoracic level may be an alternative strategy in the management of intractable visceral pain due to abdominal or pelvic cancers.