Epidemiology of focal and generalized dystonia in Rochester, Minnesota.

The epidemiology of generalized and focal dystonias was investigated in the Rochester, Minnesota, population over the period 1950-1982. The crude incidence of generalized dystonia was 2 per million persons per year, and for all focal dystonias combined, 24 per million per year. The crude prevalence rate was 34 per million persons for generalized dystonia and 295 per million persons for all focal dystonias. Torticollis was the most common focal dystonia; essential blepharospasm, oromandibular dystonia, spasmodic dysphonia, and writer's cramp were less common and had roughly equal incidence and prevalence rates.