Abstract
Temporomandibular joint disorders (TMDs) typically manifest with symptoms and signs such as pain, mandibular movement, dysfunction, or joint sounds. Botulinum toxin type A (BTX/A) is a biological toxin that inhibits the release of the neurotransmitter acetylcholine at the neuromuscular junction. This toxin is used to treat hyperactivity of masseter muscles and TMD symptoms. This case report aimed to investigate the effects of BTX/A injection in the masseter and lateral pterygoid muscles of a patient with painful symptoms of TMDs via electromyography (EMG), with a follow-up of six months post-treatment. During each visit, the clinical effects, which were evaluated based on pain intensity (NPRS), the bruxism questionnaire, and maximum mouth opening, were evaluated at five-time points, pre-injection and 2, 6, 12, and 24 weeks after the injection. Based on this case report, there was a clear improvement in the studied parameters, with a significant decrease in the electromagnetic activity of the injected muscles as shown by EMG; thus, BTX/A can be considered an effective treatment to relieve symptoms and improve the quality of life in patients with TMDs of muscular origin, relying on EMG as an effective diagnostic tool and for subsequent evaluation of treatment results.
Highlights
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Use of electromyography for accurate diagnosis of muscular temporomandibular joint disorders.
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How to inject botulinum toxin into the lateral pterygoid muscle.
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The use of botulinum toxin as an effective treatment for bruxism and muscular TMJ disorders.
1
Introduction
Temporomandibular joint disorders (TMDs) are a term that refer to a number of pathological conditions and disorders related to the temporomandibular joint (TMJ) and its associated musculoskeletal structures [ ].Muscular temporomandibular joint disorders are a common cause of orofacial pain . [ ]Although it can appear at any age, the maximum incidence is observed in young adults, between 20 and 40 years of age, predominantly in women, at a ratio of 4/1 with respect to men [ ]. The most common symptom is pain, which is accompanied by other symptoms, such as articulatory sounds, and the limitation or asymmetry of mandibular movement [ ]. These symptoms may result from oral habits such as clenching, bruxism, psychological disorders, anxiety and depression [ ]. Therefore, treatment is necessary to relieve or eliminate pain and restore normal function of the mandible. There are many therapeutic methods including drug treatment with nonsteroidal anti-inflammatory and muscle relaxants [ ] occlusal splint, physical therapy [ ], acupuncture [ ] and Botox injections [ ]. Botulinum toxin type A (BTX/A) is a neurotoxin that inhibits the release of the neurotransmitter acetylcholine at the neuromuscular junction with the goal of reducing excessive contraction of the target muscle [ ]. The US Food and Drug Administration has approved the use of BTX/A in the treatment of hemifacial spasm, cervical dystonia, and hyperhidrosis and for cosmetic treatment [ ]. BTX/A is an effective treatment method for Muscular temporomandibular joint disorders because it has a clear role in relieving pain [ ], improving symptoms and removing muscle spasm during the period of effect [ , ]. The aim of this study was to investigate the effects of BTX/A injection in the masseter muscles of a patient with bruxism, limited mouth opening and masticatory muscle pain via electromyography (EMG).
2
Case description
A 39-year-old; female patient who attended the Oral and Maxillofacial Surgery Hospital at the Faculty of Dentistry, Damascus University on January 2024, suffered from severe facial pain that increased upon waking in the morning, with limited mouth opening, and pain when chewing, especially solid food, that began 3 months before the first appointment. During treatment, she relied on pain relievers (paracetamol 500 mg) with NSAIDs (diclofenac potassium 50 mg). The pain then worsened, and these medications became ineffective.
The clinical examination revealed pain when the masseter muscles were palpated and limited mouth opening, as the patient’s maximum mouth opening value was 34 mm. The bruxism questionnaire score was 100 % patient-reported ( Table 1 ).
| 1. Do you think you clench your teeth (bruxism) while you sleep? |
| 2. Has anyone ever told you about bruxism during sleep? |
| 3. Do you have a stiff jaw or facial spasm when you wake up in the morning? |
| 4. Do you grind your teeth or bruxism during the day? |
The pain score was recorded by the patient as an overall assessment of pain at rest and function on the numeric pain rating scale (NPRS). 0 indicates no pain while 10 is the worst pain that can be expected. The patient had a score of 10 (i.e., worst pain).
Electromyography of the masseter muscles via the patient’s EMG device (Micromed Matrix EP Light, Medical Expo, Italy) revealed hyperactivity in both the masseter ( Fig. 1 ) and lateral pterygoid muscles ( Fig. 2 ) bilaterally.
Electromyography of the masseter muscle: A special gel (EEG Paste, AQUA Medical) is applied to the surface electrodes, which are placed parallel to the fiber of the masseter muscle and approximately in the middle of the muscle and fixed for accurate measurement. While the ground electrode is placed on the middle of the forehead, its function is to distort and remove noise (as shown in Fig. 3 ). The patient is asked to bite hard on the teeth clenched in the central occlusal position, and the measurement is taken to give three values, the highest, the lowest and the difference between them is estimated in (μv).
Electromyography of the lateral pterygoid muscle: the first surface electrode is placed in front of the ear, the ground electrode is placed in the middle of the forehead, and the Botox EMG needle (technomed medical accessories) is used as a deep electrode for electromyography, followed by measurement and injection ( Fig. 4 ). Correct access is indicated by the absence of interference in the diagram that appears on the screen and by the change in values depending on muscle activation ( Fig. 5 ).
Botulinum toxin injections were introduced as a solution for muscles that showed hyperactivity on the EMG machine. Botox was prepared by mixing a vial containing 100 units (TOXTA, Allergan, Inc.) with 2 ml of saline so that in 1 ml, 50 units of Botox were obtained, and 5 units were obtained every 0.1 ml ( Fig. 6 ).
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