Does the Use of Botulinum Toxin in Treatment of Myofascial Pain Disorder of the Masseters and Temporalis Muscles Reduce Pain, Improve Function, or Enhance Quality of Life?

Abstract

The efficacy of botulinum toxin for management of myofascial pain disorder (MPD) remains controversial. The purpose was to determine if the use of onabotulinumtoxinA (onabotA) in patients with MPD reduces pain, improves function, or enhances quality of life (QoL). This is a multicenter, prospective, randomized, double-blinded, placebo-controlled clinical trial. Subjects with orofacial pain were screened for MPD as defined by the Diagnostic Criteria for Temporomandibular Disorders. The primary predictor variable was MPD treatment with random assignment to onabotA or placebo (saline). The primary outcome variable was pain before treatment (T0) and at 1month (T1) using a visual analog scale. Secondary outcome variables included pain at 2months (T2) and 3months (T3), maximal incisal opening (MIO), jaw function (jaw functional limitation scale), and QoL (Short Form 36) measured at T0, T1, T2, and T3. Covariates included subject demographics, prior treatments, and temporomandibular joint signs/symptoms. Descriptive and bivariate statistics included χ2 test, Fisher's exact test, or t-test. Seventy five subjects with a mean age of 37 (±11) and 35 (±12) years in the onabotA and placebo groups, respectively (P=.6). Females represented 32 (86%) and 29 (76%), respectively (P=.3). Mean visual analog scale pain score in the onabotA group was 58 (±15), 39 (±24), 38 (±23), and 38 (±20) at T0, T1, T2, and T3, respectively; and the placebo group was 54 (±14), 40 (±23), 34 (±20), and 36 (±22) at T0, T1, T2, and T3, respectively. There was no statistically significant difference in pain between groups at any time point (P=.36). There was no statistically significant difference between groups in MIO (P=.124), jaw function (P=.236), or QoL domains (P>.05) at any time point. Within-group improvement in pain was seen in both groups (P<.005). Within-group improvement in jaw function was seen in the onabotA (P=.007) and placebo (P=.005) groups. There was no within-group improvement in MIO or QoL with either group (P>.05). OnabotA and saline (placebo) injections both decrease pain and improve jaw function in subjects with MPD.