Long-term effects of botulinum toxin A injection on pain and quality of life in patients with myofascial pain of masticatory muscles: a retrospective study

Introduction
Favorable effects of botulinum toxin type A (BoNT/A) on muscle hyperactivity and pain has led to its’ use in the treatment of temporomandibular joint disorders, related to muscle pain and masticatory myofascial pain.

Objectives
The aim of this retrospective study was to evaluate the short- and long-term effects of trigger point injections of BoNT/A in patients with myofascial pain syndrome.

Material and methods
The study included 17 individuals aged 19-57 years (mean, 33 years), with 2 years of follow-up records. Visual analogue scale (VAS), pressure-pain threshold (PPT), and maximum mouth opening (MMO) were applied to evaluate pain and dysfunction. Mood and sleep quality were assessed using Beck’s depression inventory (BDI) and Pittsburgh sleep quality index (PSQI). All evaluations were repeated before (T0) as well as at 4 weeks (T1), 6 months (T2), and 2 years (T3) after BoNT/A injection.

Results
VAS score was lower at all 3 post-injection time points compared to T0 (p < 0.001). Significant increases in PPT and MMO measurements were also observed at T1, T2, and T3 compared to T0. BDI scores were significantly reduced at T1 and T2 compared to T0 (p < 0.05). PSQI decreased significantly between T0 and T1 (p < 0.001), but increased at T3 (p < 0.05).

Conclusions
BoNT/A injections are an effective treatment alternative that relieve myofascial pain and mouth opening restriction, and subsequently improve quality of life in both the short- and long-term.