Onabotulinum toxin A block of the sphenopalatine ganglion in patients with persistent idiopathic facial pain: a randomized, triple-blind, placebo-controlled, exploratory, cross-over study

To investigate the efficacy and safety of injecting onabotulinum toxin A (BTA) towards the sphenopalatine ganglion (SPG) using the MultiGuide® in patients with persistent idiopathic facial pain (PIFP).This cross-over, exploratory study compared the injection of 25 units BTA versus placebo in patients who met modified ICDH-3 criteria for PIFP. Daily pain diaries were registered for a 4-week baseline, a 12-week follow-up after each injection, and an 8-week conceptual washout period in between. The primary efficacy endpoint was the change from baseline to weeks 5-8 in average pain intensity using a numeric rating scale. Adverse events were recorded.Of 30 patients who were randomized to treatment, 29 were evaluable. In weeks 5-8, there was no statistically significant difference in average pain intensity between BTA versus placebo (0.00; 95% CI = -0.57 to 0.57) (P = 0.996). Following both BTA and placebo injections, five participants reported at least a 30% reduction in average pain during weeks 5-8 (P = 1.000). No serious adverse events were reported. Post-hoc analyses indicated a possible carry-over effect.Injection of BTA toward the SPG with the MultiGuide® did not appear to provide a reduction in pain reduction at 5-8 weeks, although this finding may be influenced by a carry-over effect. The injection appears to otherwise be safe and well-tolerated in patients with PIFP.Trial Registration: The study protocol is registered in ClinicalTrial.gov (NCT03462290) and EUDRACT (number: 2017-002518-30).