A prevalence study of primary dystonia in eight European countries

There have been few epidemiological studies of dystonia. Most previous stud ies have provided estimates based on few cases. A European prevalence study was undertaken to provide more precise rates of dystonia by pooling data f rom eight European countries. Diagnosed cases were ascertained by adult neu rologists with specialist movement disorder land botulinum toxin) clinics. The crude annual period prevalence rate (1996-1997) for primary dystonia wa s 152 per million (95 % confidence interval 142-162), with focal dystonia h aving the highest rate of 117 per million (108-126). Prevalence rates for c ervical dystonia, blepharospasm and writer's cramp were as follows: 57 (95 % confidence interval 51-63), 36 (31-41), and 14 (11-17). The age-adjusted relative rates were significantly higher in women than in men for segmental and focal dystonias with the exception of writer's cramp. Comparing rates between centres demonstrated significant variations for cervical dystonia, blepharospasm and writer's cramp, probably due to methodological difference s. Our results provide the first data on the prevalence of primary dystonia and its subtypes across several European countries. Due to under-ascertain ment of cases, our rates should be seen as conservative and an under-estima te of the true prevalence of dystonia.