Prevalence and diagnostic challenge of dystonia in Thailand: a service-based study in a tertiary university referral centre.

Although the subspeciality of movement disorders was established in neurology more than 20 years ago, it is relatively new in Thailand, and while most physicians are generally aware of Parkinson's disease, they often are not familiar with dystonia. As one of the common movement disorders seen in general practice, a number of family and population studies have suggested that as many as two-thirds of patients with dystonia may be underdiagnosed and it is likely that misdiagnosis occurs frequently. Moreover, there is little information on the prevalence of dystonia in Thailand. The purpose of this study was to determine the prevalence and clinical profile of dystonia among Thai patients who came from the southern part of Bangkok, which is in the catchment area of Chulalongkorn University Hospital. In addition, the diagnostic accuracy of dystonia among referred patients was assessed. The medical records of 207 patients were reviewed and it was determined that a large proportion of them (71.9%) had focal dystonia with cervical dystonia being the most common form. Primary dystonia (68.1%) accounted for the majority of the cases. The prevalence of all forms of dystonia, primary dystonia and focal dystonia was 19.9, 13.6 and 14.3 per 100,000 persons, respectively. The diagnostic accuracy of dystonia among referred patients was 85.5%. The most common misdiagnosis was cervical spondylosis, followed by myofascial pain syndrome. Most patients had an average disease duration of 4 years before dystonia was finally diagnosed. Most patients with focal dystonia responded well to botulinum toxin therapy, with 13.3% suffering only mild transient adverse events. In spite of the limitations of this study, this data will initiate a process of increasing both patient and professional awareness of dystonia in Thailand.