Case history and examination
The patient is a 53-year-old woman who‘s symptoms had lasted for over 30 years and the pain was troublesome 1-3 times per month. She sought treatment for facial pain and headache and self-reported bruxism. The patient had no systemic diseases, no medication and did not smoke. She had self indentified that symptoms correlatated often with stress episodes. The patient was treated with many different TMD treatment modalities such as splint therapy, non-steroidal anti-inflammatory drugs medication and soft food diet, but with poor success.
The clinical examination revealed a maximum mandibular opening of 50 mm and a normal range of eccentric movements. No joint pain or sound was noted. There was a stable occlusal condition in a musculoskeletal stable position. According to the pain drawing, the pain that the patient experienced during the last six months was intraorally and in the areas of the head, neck, face, and shoulders throughout. Palpation of the muscles of mastication revealed muscle tenderness in the areas of the masseter and temporalis with no referred pain. Palpation-induced pain was familiar to the patient. The diagnosis was local myalgia and headache attributed to TMD secondary to parafunctional activity and stress-related muscle co-contraction. Since the symptoms were lasting for years and the conservative treatments of muscle pain were ineffective, activity within central nervous system (CNS) could be involved in the pain input. The diagnosis of centrally mediated myalgia could not be excluded. In this investigation we decided to try botulinum toxin injections as a treatment option and combined with comprehensive assessments of the treatment responses.
The Characteristic Pain Intensity (CPI) score was calculated from the 0-10 ratings of current, worst, and average pain intensity during the past six months. Before the treatment the score was 7.3. The chronic pain grade (CPG, baseline to six months, grades 0-IV) was II, corresponding to ‘High intensity pain, without disability’. Jaw functional limitations were observed in the following activities: chewing tough food, smiling, yawning, and tooth brushing. The degree of pain-related worry was 7 (0-10 scale). Based on the Symptoms Checklist-90 Revised (SCL-90R) questionnaire, the patient had only mild symptoms of depression, with an average score of 0.5 (0-4 scale). The same questionnaire revealed severe sleep disorder, with an average score of 3.0 (0-4 scale). The average score of non-specific physical symptoms with pain items was 0.6 and non-specific physical symptoms without pain items 0.4 (0-4 scale). The initial average electromyography (AEMG) value of the masseter muscle during clenching with maximum force was 241 mV and at rest 45 mV, and the average maximum bite force was 580 N (Figure 1).
Clinical diagnosis was based on the standardized clinical examination protocol and Axis I decision tree of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) [6]. Axis II bio­psychosocial assessment instruments of the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were used to evaluate the effect of treatment on disability and psychological status [7]. The following questionnaires were used before the treatment and at each follow-up visit:
Axis I (Physical findings)
Demographics
Clinical examination form (DC/TMD)
Axis II (Disability & Psychological Status)
GCPS 1.0 grades are derived from seven questions measuring
EMG of masseter muscle and bite forces were assessed before the treatment and after the botulinum toxin injections at each follow-up visit. A series of recordings consisted of an exercise lasting 60 seconds so that every 10th second the patient was asked to bite hard for 5 seconds followed by a 5-second relaxation. The values of AEMG were selected from the middle of each 5-second relaxation and clench periods. Maximum bite force was selected from each clench period. Six values of AEMG and bite force were selected at each patient’s visit, and the average values were calculated.
The patient received a one-time treatment of 50 units of BoNT-A (Xeomin®, supplied by Merz Pharmaceuticals GmbH, Germany); 2/3 of the dose was injected into the bilateral masseter muscles (16.7 units each masseter) and 1/3 into the bilateral temporalis (8.3 units each temporalis). Three injections were applied along the inferior border of the masseter and two injections along the anterior part of the temporalis. Follow-ups were performed at 2, 11, 16, and 22 weeks after the botulinum toxin injections.
At two weeks after the injections, there were no significant changes in pain location, pain intensity, or degree of disability, with chronic pain grade remaining at II and CPI 6.7. However, functional limitations were no longer observed. The score for pain-related worry level was 6 (range 0-10). The following scores were obtained from the Axis II biobehavioural questionnaire (range 0-4): symptoms of depression 0.45, sleep dysfunction 1.7, and non-specific physical symptoms with and without pain items 0.3. The AEMG value during clenching with maximum force dropped to 55 mV and the average maximum bite force to 305N (Figure 1). No changes occurred to AEMG rest (45 mV).
At 11 weeks after the injections, only the parietal region remained as a pain area. The chronic pain grade was 0, meaning that TMD pain and its related disability were no longer present. No functional limitations were observed. Pain-related worry level was 1 (range 0-10). The following scores were obtained from the Axis II biobehavioural questionnaire (range 0-4): symptoms of depression 0.35, sleep dysfunction 1.0, and non-specific physical symptoms with pain items 0.2 and without pain items 0. The AEMG value during clenching with maximum force was 74 mV, and the average maximum bite force was 326 N (Figure 1).
At 16 weeks after the injections, the pain distribution level was moderate with two areas affected: the temporalis and the right side of the neck. The severity of chronic pain was graded as II and CPI was 6.0. Nonetheless, no functional limitations were observed. Pain-related worry level was 5 (range 0-10). The following scores were obtained from the Axis II biobehavioural questionnaire (range 0-4): symptoms of depression 0.3, sleep dysfunction 1.7, and non-specific physical symptoms with pain items 0.3 and without pain items 0.1. The AEMG value during clenching with maximum force was 98 mV, and the average maximum bite force was 488 N (Figure 1).
At 22 weeks after the injections, the pain distribution level was still moderate, affecting the parietal and temporal regions. CPI score was 0, with no functional limitations. Pain-related worry level was 5 (range 0-10). The following scores were obtained from the Axis II biobehavioural questionnaire (range 0-4): symptoms of depression 0.25, sleep dysfunction 1.0, and non-specific physical symptoms with pain items 0.2 and without pain items 0. The AEMG value during clenching with maximum force was 133 mV, and the average maximum bite force was 452 N, indicating that the physiological effect of BoNT-A was still present (Figure 1).