Prevalence of primary focal or segmental dystonia in adults in the district of Foggia, southern Italy: A service-based study

Background: Primary focal or segmental dystonia is a rare clinical condition including early-onset dystonia, which has the tendency to generalize, and late-onset dystonia, which may be focal or segmental. The prevalence of late-onset dystonia ranges from 30 to 7,320 cases per million, but no data are available in Italy. Methods: A service-based study was conducted in the period 1 January 2001 through 31 December 2002 in the administrative district of Foggia, southern Italy (population 541,653). Cases were traced through hospital discharge diagnosis, botulinum toxin services, day hospital access, ear, nose and throat, ophthalmology and orthopedic surgery specialists, and territorial outpatient services. Inclusion criteria were age 17 years or older, residency in the study area and a diagnosis of primary focal/segmental dystonia. Results: A total of 69 patients were included, giving a crude prevalence of 127.4 per 1,000,000 (women: 146.4; men: 107.0; age 18-34 years: 39.2; 35-54 years: 98.7; 55-74 years: 273.6; 75+ years: 163.3). The standardized rate was 137.5 (95% confidence interval 107.0-174.6). Blepharospasm was the commonest clinical condition (prevalence 68.2), followed by cervical dystonia (prevalence 44.8). Conclusion: The prevalence of primary focal or segmental dystonia in Italy is in keeping with several other reports, but is lower than in studies performed in northern Europe, Minnesota, USA, and Japan. The difference in our results may be mostly explained by misdiagnosis, underascertainment of cases and a fairly limited observation period.