Epidemiology of primary focal dystonias in the western area of Tottori prefecture in Japan: Comparison with prevalence evaluated in 1993.

An epidemiological survey of primary focal dystonias in the western area of Tottori Prefecture in Japan was conducted in 2003, and the results were compared with those of a previous survey in 1993. The service-based prevalence of primary focal dystonia was 13.7 per 100,000 population, representing an increase from that found in the 1993 survey. In 1997, botulinum toxin type A was approved for use in Japan to treat blepharospasm, and the increased number of patients now being evaluated and diagnosed with focal dystonias at medical centers throughout Japan may be responsible for this increased prevalence. Prevalence by subtype per 100,000 population was as follows: facial dystonia, 6.5; spasmodic torticollis, 2.0; writer's cramp, 4.4; and other focal dystonias; 0.8. Facial dystonia showed the most marked increase in service-based prevalence among these subtypes.