Prevalence of primary focal and segmental dystonia in Oslo.

All patients seeking medical treatment for primary focal and segmental dystonia in Oslo, Norway, were identified in a service-based prevalence study. A total of 129 patients with focal and segmental dystonia were treated. The total prevalence was 25.4 per 100,000, but the prevalence increased with age from 4.1 (age < 30) to 58.7 (age > 70). The prevalence in subjects of European descent was 28.3 per 100,000, much higher than among first-generation immigrants of Asian and African descent.