Botulinum toxin for myogenous orofacial pain : a randomized controlled trial

Objective: The purpose of this study was to assess the effectiveness of Botulinum toxin A (BTX-A) in the treatment of refractory chronic myogenous orofacial pain. Methods: A randomized double-blind clinical trial was conducted comparing BTX-A (BOTOX, Allergan inc, Irvine, CA) to saline injection. Nineteen subjects (16 females, 3 males) were randomly assigned to receive either 200 U of BTX-A (n=9) or the same volume of saline water (n=10) into the temporalis (40 U) and masseter muscle (60 U). Data were collected at baseline (T0), 3 (T1), 7 (T2), 11-15 (T3), and 24 (T4) weeks post-treatment. Primary outcome variables monitored with Visual Analog Scales (0-10) included: global pain severity (GPS), present pain intensity (PPI), pain relief (PR) and muscle pain intensity evoked with a pressure algometer (MPIA). Data were analysed using repeated-measures ANOVA with p-level set at 0,05. Thirteen subjects completed the follow-up period at six months. Results: A group by time effect was observed in the BTX-A group for the semi-objective outcome variable MPIA (p=0.0081). Although, no statistically significant differences were observed for the subjective outcome variables, the magnitude of changes from baseline to T1 and T2 was greater in the BTX-A group for GPS (18% vs 3%; 47% vs 28%) and PPI (48% vs 5%; 51% vs 11%). Pain relief (PR) was also greater in the BTX-A group at T1, T2 and T3 (5,1 vs 2,2; 5,4 vs 2,7; 5,4 vs 3,8). Conclusions: Within the limit of this pilot study, these results tend to indicate that BTX-A has a moderate and faster short-term effect on myogenous orofacial pain. Studies assessing cost-effectiveness are however needed to fully assess this treatment modality.

(This project was supported by Fonds André Charest, Université Laval (grant #FO080730), the Canadian Association of Oral and Maxillofacial Surgeons and Allergan inc., Irvine, CA who provided BTX-A).