Prevalence and incidence of oromandibular dystonia: an oral and maxillofacial surgery service-based study.

OBJECTIVES: Oromandibular dystonia is a focal dystonia characterized by sustained or intermittent contractions of the masticatory and/or tongue muscles. This epidemiological study aimed to estimate the prevalence and incidence of oromandibular dystonia in Kyoto (population: 1,465,701). MATERIALS AND METHODS: The population sample was citizens of Kyoto who visited our department between 2015 and 2019 and were differentially diagnosed by an oromandibular dystonia specialist having idiopathic (primary) and acquired (secondary) oromandibular dystonia. A total of 144 patients (100 women and 44 men; mean age, 57.5 years) were analyzed for clinical features, and the prevalence (prevalence date, January 1, 2020) and annual incidence were estimated. RESULTS: The male-to-female ratio was 1:2.3 (p<0.001). Age at onset was significantly (p<0.01) earlier in men (47.5 years) than that in women (56.9 years). The crude prevalence of oromandibular dystonia was estimated at 9.8 per 100,000 persons (95% confidence interval: 8.3-11.6) (idiopathic dystonia, 5.7 [4.6-7.1]; tardive dystonia, 3.4 [2.5-4.5]) and incidence at 2.0 (1.3-2.8) per 100,000 person-years (idiopathic dystonia, 1.2 [0.68-1.9], tardive dystonia, 0.68 [0.32-1.3]). The prevalence was 13.0 (10.5-15.8) in women and 6.3 (4.6-8.5) in men. All age groups showed female predominance. The highest prevalence was 23.6 (14.4-36.5) in women aged 60-69 years. CONCLUSIONS: As this is an oral and maxillofacial surgery service-based study, the actual prevalence of oromandibular dystonia may be even higher. CLINICAL RELEVANCE: It was suggested that oromandibular dystonia might be more common than cervical dystonia or blepharospasm.