Clinical and neurophysiologic features of tremor in bruxism and focal dystonias

Background. The similarity of tremor characteristics in patients with bruxism and muscular dystonia has been noticed in clinical practice. During a search in scientific databases, it was found that tremor in patients with bruxism is a topic of interest but little studied. It is similar to dystonia in its characteristics, this may be a confirmation of the long discussed hypothesis in scientific research that bruxism is a form of muscular dystonia. Research objective. To analyze and compare the characteristics of tremor in patients with bruxism and focal dystonias. Material and Methods. In a single-center open comparative clinical study on the basis of the Central Institute of Botulinum Therapy and Topical Neurology 60 people (10 % men; average age 38+/-15 years) participated. Of these, 30 were diagnosed with bruxism (group «bruxism») according to the criteria developed by the American Academy of Sleep Medicine (AASM), 30 were diagnosed with cervical dystonia (group «dystonia») according to Clinical Guideline #163 «Dystonia». All participants underwent tremorography, then the data were analyzed and the results were statistically processed. Results. In the «bruxism group, 100 % of the subjects (30 patients) were found to have mandibular tremor: fine-spaced, low-amplitude, predominantly kinetic, asymmetric, irregular varied-frequency and varied-amplitude with tremor frequency averaging 5 Hz (from 2 to 9 Hz, most often 3–8 Hz). In 60 % of patients in this group, asymmetric postural-kinetic hand tremor was found, fine-spaced, low amplitude, with frequency peaks of 4.5–5.76 Hz and 10–12 Hz. A high coherence was found between mandibular tremor and hand tremor in patients with bruxism at 3.77–5.41 Hz). In the «dystonia» group, 100 % of subjects (30 patients) were found to have head tremor: fine-spaced, low-amplitude, predominantly kinetic, asymmetric, irregular varied-frequency and varied-amplitude tremor with an average frequency of 4.5 Hz (from 1.8 to 9 Hz, most often 2.5–7.5 Hz). Asymmetric postural-kinetic hand tremor was found in 66 % of patients, fine-spaced, low-amplitude, with frequency peaks of 3.5–5.16 Hz and 10–12 Hz. High coherence between head tremor and hand tremor was found in patients with dystonia at 3–5 Hz). Conclusion. Comparison of neurophysiologic parameters of tremor tremor in bruxism and cervical dystonia revealed similarity of parameters, which may indicate the commonality of etiopathogenesis. The obtained data suggest that bruxism is a special form of muscular dystonia. The identified parameters require further study and can be used for early diagnosis of bruxism.