New pain following cordotomy: clinical features, mechanisms, and clinical importance

Object. The clinical features, possible causes, and contributing factors as sociated with novel spontaneous pain following unilateral cordotomy were in vestigated to clarify the mechanism and clinical importance of this pain. Methods. Forty-five patients who underwent cordotomy for severe unilateral cancer pain were included in this study. New pain occurred in 33 (73.3%) of 45 patients. Pathological conditions of tissue demonstrated on imaging cor responded to new pain in eight patients, referred pain in five, and neither of these in 15 patients. New pain was centered opposite the site of the or iginal pain in a mirror-image location in 28 patients and rostral to the or iginal pain in five patients. It was temporary in seven patients, weaker th an the original pain in 25, and as severe as the original pain in one patie nt. The incidence of moderate or severe pain was significantly higher in pa tients with confirmed tissue disease (six of eight patients) than in those without (six of 20 patients). An important contributing factor to the occur rence of new pain was the achievement of analgesia by performing the cordot omy. Conclusions. The present results indicate that new pain occurs frequently a fter unilateral cordotomy. Nonetheless, cordotomy may still be indicated fo r unilateral uncontrollable pain because new pain, when present, was weaker and more easily controlled than the original pain in nearly all cases. The authors speculate that new pain may represent a type of referred pain from the original painful area or may arise from sensitization of contralateral spinal nociceptive circuits due to metastasis or tumor infiltration, and t hat new pain is potentiated by the interruption of descending inhibitory pa thways.