[Primary focal dystonia: descriptive study of 205 patients]

To describe the clinical and epidemiologic aspects of different types of focal dystonia.

A total of 205 patients with primary focal dystonia were studied retrospectively and the following variables were analyzed: gender, age of onset, age at examination, evolution time, history of trauma, association with other movement disorders, fluctuations of dystonic symptoms as well as a family history of dystonia, Parkinson's disease, tremor, and lefthandedness or stuttering. We compared these variables among the different clinical categories of focal dystonia.

Those patients with cranial and laryngeal dystonia were significantly older at the onset of symptoms compared with patients with writer's cramp. Males were more prevalent than females in all categories of focal dystonia except for cranial dystonia. Prior history of trauma and association with tremor were more frequent in patients with cervical dystonia than in those with others dystonic categories. Most patients with cranial, cervical and laryngeal dystonia had fluctuations in the intensity of dystonic symptoms, unlike the patients with writer's cramp.

There is a caudo-cranial gradient in age of onset and the age of onset increases as the cranial presentation becomes greater. Females are more prevalent in cranial dystonia and there is a preponderance of males in the dystonias with a lower location. The dystonias with cranial distribution frequently present fluctuations of symptoms during the day. Association with other movement disorders, such as tremor, and prior history of trauma, is common in patients with cervical dystonia.