Efficacy of botulinum toxin type A for treatment of persistent myofascial TMD pain: A randomized, controlled, double-blind multicenter study

Abstract

Evidence of an effect by botulinum toxins is still lacking for most pain conditions. In the present randomized, placebo-controlled, crossover multicenter study, the efficacy of botulinum toxin type A (BTX-A) was investigated in patients with persistent myofascial temporomandibular disorders (TMD). Twenty-one patients with myofascial TMD without adequate pain relief after conventional treatment participated. A total of 50 U of BTX-A or isotonic saline (control) was randomly injected into 3 standardized sites of the painful masseter muscles. Follow-up was performed after 1 and 3 months, followed by a 1-month washout period, after which crossover occurred. Pain intensity at rest was the primary outcome measure, while physical and emotional function, global improvement, side effects, and clinical measures were additional outcome measures. There was no main difference between drugs (ANOVA; P=.163), but there was a significant time effect (P<.001), so BTX-A reduced mean (SD) percent change of pain intensity by 30 (33%) after 1 month and by 23 (30%) after 3 months compared to 11 (40%) and 4 (33%) for saline. The number of patients who received a 30% pain reduction was not significantly larger for BTX-A than after saline at any follow-up visit. The number needed to treat was 11 after 1 month and 7 after 3 months. There were no significant changes after treatment in any other outcome measures, with the exception of pain on palpation, which decreased 3 months after saline injection (P<.05). These results do not indicate a clinical relevant effect of BTX-A in patients with persistent myofascial TMD pain.

Clinical Aspects of the Use of Botulinum Toxin Type A in the Treatment of Dysfunction of the Masticatory System

“…The effect of the injection is usually temporary. Injections should be repeated, although there are a few reports of permanent results through the elimination of pathological muscle memory and restoration of physiological pattern [2,4]. These observations and results suggest a positive therapeutic effect of repeated injections of TBX-A on MSDs.…”

“…Reports in the literature state that two injections are normally performed to a depth of 3-4 cm, 1 cm below the central part of the zygomatic arch and 0.5-1 cm outward from that point, just in front of the condylar processes of the mandible. Before the injection, the mandible is placed back in its position, and after the botulinum toxin application, it is immobilized with an elastic band for 4-5 days [4,11]. For TMJ disc dislocation it is sufficient to use a TBX-A injection in the lateral pterygoid muscle.…”

“…To evaluate the effectiveness of therapy with TBX-A, Ernberg et al used the VAS (Visual Analogue Scale), which expresses the subjective feeling of pain experienced by the patient. Patients diagnosed with MSDs were assessed twice a day, in the morning and in the evening, ranking the pain intensity on a scale of 0-10, where 0 is no pain and 10 is the worst imaginable pain [4]. In this way, a pain relief scale (PRS) was developed, which specifies the impact of pain on daily activities and the number of days on which patients refrained from their usual activities (work, school, household chores, etc.).…”

“…The literature also mentions other side effects following the injection of TBX-A: fatigue, headache, muscle weakness, flu-like symptoms, dry mouth, and pruritus [2,4,6,13]. Incorrect deposition of TBX-A to the vascular system causes the symptoms of botulism.…”

“…The local paralysis is reversible; neuron regrowth occurs after 2-4 months. Muscles treated with TBX-A are less sensitive to palpation [4]. Its effect provides the possibility of inactivating a hyperactive muscle without affecting muscles not subject to spasticity or those in which it is desirable.…”