Focal dystonia, with special reference to writer's cramp.

If focal dystonia affects the hand muscles writer's cramp will result, but also other types of activity when the task involves repetitive movements such as typing and playing the piano. Writer's cramp is described, both simple and dystonic, and also the possibility of genetic causes, especially in the latter group. The characteristics of the electromyogram in this condition are discussed. The possible causes of focal dystonia and writer's cramp are reviewed: both the role of excitatory and inhibitory mechanisms and how these may influence treatment. Various treatments have been tried, and the most effective seems to be the use of botulinum toxin. However, if this does not relieve the symptoms, operations such as stereotactic lesions of the basal ganglia may be justified.