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

Objective 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). Methods 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. Results 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. Conclusions 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).