Mechanism of dexmedetomidine preconditioning on spinal cord analgesia in rats with functional chronic visceral pain

Purpose: To analyze the effect and mechanism of dexmedetomidine (DEX) analgesia pretreatment on functional chronic visceral pain in rats. Methods: Rats were divided into six groups: W1, W2, W3, W4, W5, and W6. The behavioral changes and electrophysiological indexes of rats in each group before and after DEX treatment were detected. Results: The levels of abdominal withdrawal reflex (AWR) in W5 and W6 groups were significantly lower than those in group W3, while the levels of thermal withdrawal latency (TWL) and mechanical withdrawal threshold (MWT) were significantly higher than those in group W3 (p < 0.05). The electromyographic signals of W1, W5, and W6 groups showed little fluctuation, while those of groups W2, W3, and W4 showed obvious fluctuation. TLR4 mRNA expression, IRF3, P65, and phosphorylation levels in W4, W5, and W6 groups were significantly lower than those in group W2 (p < 0.05). Conclusions: Dexmedetomidine epidural anesthesia pretreatment could significantly inhibit visceral pain response in rats with functional chronic visceral pain, and its mechanism was related to the activation of TLR4 in spinal dorsal horn tissue of rats and the activation inhibition of IRF3 and P65 in the downstream key signals.

Midthoracic Punctate Midline Myelotomy for Treatment of Chronic, Intractable, Nonmalignant, Abdominal Visceral Pain: 2-Dimensional Operative Video.

Punctate midline myelotomy (PMM) is a surgical procedure that damages the ascending fibers of the postsynaptic dorsal column (PSDC) pathway to interrupt visceral pain transmission.1-3 It can offer relief to patients with chronic visceral pain conditions that are refractory to other treatments. Here, we present a surgical video of midthoracic PMM in a patient with chronic, intractable, nonmalignant visceral abdominal pain that failed over a decade of medical treatment. We choose T7-8 as the level for laminectomy in patients with pelvic or lower abdominal pain, because the postsynaptic pain fibers transmitting visceral pain sensation from the lower abdominal organs will invariably be caudal to this level. The patient developed immediate and complete relief of her visceral pain after the procedure, which was sustained through the 11-wk follow-up period to date and was able to be weaned off narcotics. Postoperatively, she remained full strength and had no impairment of light touch or proprioception of her lower extremities. Detailed physical examination showed a reduced vibratory sensation on the glabrous skin of her great toes. Regarding patient-reported sensory changes (not detected on physical examination), she reported some numbness on the insides of her feet that had resolved by 11-wk follow-up. She also reported some numbness of the vulva, but not of the vagina. However, by 11-wk follow-up, she reported this had resolved and she had normal sexual function. The only persistent sensation at 11-wk follow-up was slight tingling in her toes that was not bothersome to her.4 The patient presented in the following video consented to both the surgical procedure and the publication of her clinical history and operative video.

Punctate Midline Myelotomy for Chronic, Intractable, Non-malignant Visceral Pain: A Case Report.

Punctate midline myelotomy (PMM) has a strong anatomic and functional basis for its role in the treatment of visceral pain. The procedure derived from advances in the understanding of the postsynaptic dorsal column (PSDC) pathway and the converging laboratory and clinical evidence that this spinal cord pathway plays a dominant role in conveying visceral pain to higher levels of the nervous system. The result of PMM is a concise, effective interruption of the PSDC pathway with minimal to no side effects. While considerable evidence now documents that PMM has good efficacy and safety in treating malignant visceral pain, there is little experience describing its application to chronic severe refractory visceral pain of benign origin.  We present the case of a patient with a 13-year history of severe non-malignant chronic abdominal visceral pain who obtained complete pain relief from a PMM at the T7 level. Intraoperative somatosensory evoked potential (SSEP) monitoring did not show changes after making the PMM lesion. As of six-months postoperative follow-up, the benefit shows no sign of fading, all pain medications have been discontinued, and there has been no impairment of motor function, bowel or bladder function, sexual function, gait or station. Upon detailed questioning, the patient endorsed only mild subjective reduced sensation of the inner aspects of her feet that was not bothersome to her. On detailed testing, position sense was preserved throughout; the Romberg test was negative, and the only finding was reduced vibratory sensation over the great toe pads. We cautiously suggest that the PMM operation may allow relief from severe, intractable, benign visceral pain syndromes for which effective treatments are otherwise elusive. The procedure warrants further study for such conditions.