Ganglionic local opioid analgesia in refractory trigeminal neuralgia:: Just a placebo?: A randomized, controlled, double-blind, cross-over study

Introduction: The application of opioid drugs close to sympathetic ganglia (ganglionic local opioid analgesia, GLOA) has been reported to provide good pain relief in certain chronic pain syndromes. In the present prospective, randomized, double-blind, placebo-controlled, crossover study, the analgesic efficacy of GLOA versus saline injections was compared in patients suffering from refractory trigeminal neuralgia. Methods: A total of 19 patients were treated once a day for two 5-day periods with a series of either GLOA or saline injections, respectively, using a cross-over design. All applications were exclusively performed at the ganglion cervicale superius (GCS) of the affected side. The verum-GLOA consisted of 0.045 mg buprenorphine in 1.5 ml 0.9% NaCl, the placebo-GLOA of 1.5 ml 0.9% NaCl only. Pain reduction was measured with a visual analogue scale (VAS) before and after each injection. Data were analysed using analysis of variance. Results: Surprisingly, an almost identical, significant pain relief occurred in both groups within the first week of treatment, and also after the first treatment period the extent and duration of pain reduction were similar in the two groups. Following a 2-day treatment-free interval, the second treatment period did not show any significant additional effect on the constant, lasting pain relief due to the first treatment period, irrespective of whether GLOA or saline was applied. Conclusion: The application of 1.5 ml of 0.9% NaCl with 0.045 mg buprenorphine or of pure saline (verum-GLOA or placebo-GLOA) at the ganglion cervicale superius on five consecutive days was indistinguishably effective providing a significant pain relief in patients with insufficient pain relief under standard carbamazepine medication.