Features of pain syndrome in patients with bruxism and its dynamics after treatment with botulinum neuroprotein type A

The purpose of the study. To evaluate the relationship of wakefulness and sleep bruxism with orofacial pain and the dynamics of pain syndrome after injections of botulinum neuroprotein type A. Material and methods. A single-center open prospective interventional clinical trial at the Central Institute of Botulinum Therapy and Topical Neurology involved 100 patients (90% women; age 19-39 years) with an established diagnosis of bruxism according to criteria developed by the American Academy of Sleep Medicine (AASM). Pain intensity was assessed using a Visual Analog scale (VAS); the number of days with pain, the number of nights with manifestations of sleep bruxism, the number of days with manifestations of wakefulness bruxism and the number of days with symptoms of temporomandibular joint dysfunction - according to patient diaries; the presence of a neuropathic component of pain according to the DN4 questionnaire; levels of anxiety and depression — according to the Hospital Anxiety and Depression Scale (HADS); levels of well—being, activity and the mood according to the SAN questionnaire. Also, during examination and palpation of the muscles, the presence of hypertrophy, tension and muscle soreness was assessed. 88% of patients received intramuscular injections of botulinum toxin type A drug — Xeomin® (n=69), Myotox® (n=19). Injections of the drug at a dose of 100 units were carried out once bilaterally into the masticatory muscle group (actually masticatory, temporal, lateral and medial pterygoid muscles). The duration of the study was 28 weeks, which included 6 repeat patient visits. The effectiveness of therapy was evaluated 2, 4, 8, 12, 24 weeks after injection. Results. 94% of patients with bruxism (n=94) initially had pain in the masticatory muscles, which met the criteria of "Primary myofascial orofacial pain" according to the International Classification of Orofacial Pain, 1st edition 2020. (ICOP-1). Gender and age did not affect pain in the masticatory muscles [p>0.050; multivariate analysis of variance (ANOVA)]. However, a higher level of anxiety (p=0.0133) affected the intensity of muscle pain. The total score on the DN4 questionnaire did not exceed 4 points. After BTA injections, pain regression was noted in all patients with sleep and wakefulness bruxism with initial muscle pain (n=88) (p<0.001). Pain intensity (Me [Q1‑Q3]; VAS) decreased statistically significantly (p<0.001) from 5 [4.0–7.0] points initially to 2 [1.0–4.0] points after 2 weeks (average difference -3.0; 95% CI [-4.5; — 1.8]); to 1 [0.0-2.0] points after 4 weeks (average difference -4.0; 95% CI [-5.4; — 3.6]); up to 0 points [0.0–1.0] after 8 weeks (average difference -5.0; 95% CI [-6.2; — 3.8]), remaining at the same level af ter 12 and 24 weeks after the injection. The frequency of pain also significantly decreased: from 12 [4.0–20.0] days initially to 5.5 [3.0–8.0] days after 4 weeks (average difference -6.5; 95% CI [-4.15; — 8.85]); to 2.5 [1.0–4.0] days after 8 weeks (average difference -9.5; 95% CI [-7.15; — 11.85]); up to 0 points [0.0–0.0] after 12 weeks (average difference -12.0; 95% CI [-9.65; — 14.35]) and remained at this level until 24 weeks. There was also a decrease in the frequency of days with clinical manifestations of daytime (p<0.00832) and nocturnal (p<0.00674) bruxism, symptoms of DVNHS (p<0.00832). The levels of anxiety and depression significantly decreased from 8.5 and 6.5 to 1.5 and 3.5, respectively (p<0.05). The psychoemotional state of the subjects also significantly improved according to the SAN questionnaire — the average score increased from 39.5 to 52.5 (p<0.0007). At the same time, the leveling of clinical symptoms was first noted — by 3-4 weeks after injection, then the analgesic effect. Adverse events of mild severity were noted in 70.5% of patients: pain at the injection site (31 patients), microhematomas at the injection site (22 patients), moderate weakness of the chewing muscles (25 patients), asymmetry of the corners of the mouth (1 patient). No new NSAIDs associated with treatment with botulinum toxin type A have been identified. Conclusion. Sleep-wake bruxism is associated with myofascial pain in most patients. Botulinum therapy not only significantly leads to regression of pain syndrome, but also affects daytime and nighttime manifestations of bruxism, symptoms of DVNHS, reduces the severity of anxiety and improves the psycho-emotional state of patients.