Cervical Dystonia

Epidemiology

The mean age of symptom onset in patients with cervical dystonia is approximately 41 years. However, onset is variable and may range from childhood to old age. Women are more commonly affected by CD than men, in a ratio of 2:1. Disease remissions may occur in about 20% of patients, usually during the first few years. The longer the duration of the patient's disease, the less likely they are to experience a remission.

Due to the variability of associated symptoms and disease severity and the fact that some patients with mild cases of CD may remain undiagnosed, it is difficult to determine the specific frequency of primary dystonia in the general population. However, according to a 1988 study conducted in Rochester, Minnesota, the frequency was estimated to be 29.5 individuals per 100,000 for focal dystonias.

There are few epidemiological studies on dystonia and its various forms. A large European study, reported in the literature in 2000, estimated the crude annual period prevalence rate for primary dystonia (for 1996-1997) at 152 per million. Of the primary dystonias, focal dystonia had the highest relative rate at 117 per million. The prevalence rates for cervical dystonia were estimated at 57 per million individuals. The relative rates, adjusted for age, were substantially higher in women than in men for focal dystonias such as CD. The exception to this was writer's cramp. Warner T et al. point out that these estimates should be viewed as an underestimation of the true prevalence of dystonia. Their estimates are seen as conservative due, in part, to under-ascertainment of cases.