[Botulinum toxin treatment of neurogenic dislocation of the temporomandibular joint].
Botulinum toxin leads to paresis of the skeletal muscle lasting 2-4 months via an inhibition of acetylcholine release at the neuromuscular junction. Since 1995, botulinum toxin injections have been used in the treatment of recurrent dislocation of the temporomandibular joint (TMJ). The chemical denervation of the external pterygoid muscle restricts the angle of mouth opening, thus helping to prevent dislocation. TMJ dislocations that occur as a result of increased tone in the protracted masticatory muscles were recently defined as neurogenic dislocations of the TMJ. We conducted a clinical study to investigate the efficacy of botulinum toxin injections into the external pterygoid muscle in five patients with recurrent neurogenic dislocations of the TMJ. In the 3 months prior to the first treatment, the patients had suffered a total of 19 dislocations. In the 3-month period following the initial treatment, only one woman experienced a dislocation. We performed the treatment a total of 25 times. Five dislocations occurred during the 6- to 36-month observation period. In the meantime, two patients remain recurrence-free 1 year after receiving treatment. All the patients had a restricted ability to open their mouths as a side effect of the weakening of the external pterygoid muscle that was completely reversible over the course of 3-4 months. All other side effects were equally well-tolerated by the patients and fully reversible after 3 weeks at the most. In the two patients who remain recurrence-free without any further treatment, the increased tone of the muscles serving the jaw normalised spontaneously over the course of the underlying neurological disease. Our results show that, in the treatment of recurrent neurogenic dislocations of the TMJ, botulinum toxin injections represent a therapeutic alternative that has few side effects.