Introduction
Temporomandibular disorders (TMDs) are neuromuscular and musculoskeletal
disorders affecting the jaw and muscles of mastication, with pain being
the most common complaint.
Hyperactivity of masticatory
muscles is a common background in TMD, which led to the hypothesis that
muscle relaxation with botulinum toxin may be a treatment of choice.
Botulinum toxin type A (BoNT-A) blocks the release of acetylcholine from
the presynaptic membrane, leading to abridged muscle contraction. BoNT-A
has also been suggested to have analgesic properties by blocking the
release of substance P, glutamate, and calcitonin gene-related peptide
(CGRP) [1,2].
Abundant research has shown that BoNT-A injections reduce pain in
patients with TMD, providing a new means for treating patients with
refractory symptoms [3]. Nevertheless, some studies have reported no
improvements of symptoms after treatment [4]. Contradictory results
support the multifaceted nature of TMD.
Since pain is the main symptom of
TMD, most studies have concentrated on the pain-alleviating effect of
BoNT-A, and clinical studies applying objective measurable parameters,
such as electromyography (EMG), are missing [5]. Accordingly, there
is an urgent need for controlled studies that assess subjective
complaints and compare these with objective physical findings and
provide a long-term follow-up (4-6 months).
The TMD treatment response
evaluation method presented in this case, including EMG and bite force
measurements, provides a good tool for proper evaluation of treatment
outcomes, taking into account the variable etiology and manifestation of
TMD.