Factors associated with Successful Responses to Ganglion Impar Block: A Retrospective Study

Background: The ganglion impar (ganglion of Walther) block has been used to manage coccygeal and perineal (perianal and genital) pain due to both benign and malignant causes. However, the factors associated with successful responses to ganglion impar block are unknown. Therefore, in the present study, we aimed to identify the independent factors associated with successful responses to ganglion impar block in patients with chronic pain in coccygeal and perineal regions. Methods: From January 2008 to December 2017, we performed a retrospective review of 106 patients who underwent ganglion impar block. Patients were considered successful responders if they reported a decrease of more than 50% or 4 points on the 11-point (0 = no pain and 10 = worst possible pain) numerical rating scale 1 month after the procedure, while others were considered non-responders. Logistic regression analysis was performed to identify factors independently associated with successful responses at 1 month after the procedure. Results: Multivariable logistic regression analysis showed that cancer-related causes were significantly associated with successful responses at 1 month after ganglion impar block (odds ratio = 2.60, 95% confidence interval = 1.05 to 6.43, P = 0.038). Conclusion: Ganglion impar block may be more effective in cancer-related pain than pain due to benign causes.