Clinical features of dystonia

Dystonia is a disorder characterized by involuntary movements of sustained muscle contractions, causing prolonged movements or abnormal postures. Movements are often twisting in nature, meaning rotatory about the long axis of a body part. Some patients may also have quick movements, called myoclonic dystonia, or tremor, but ordinarily there will have to be some sustained movements for dystonia to be recognized as such. These quick movements particularly might be confused with epileptic phenomena. Dystonia can be present during rest, but in general is more likely to appear when the patient is engaged in voluntary activity. Voluntary movements are slow, clumsy, and characterized by overflow (excessive activity in muscles not needed for the task).

Dystonia can be present in any part of the body, and can be classified as focal, segmental, multifocal, generalized, or hemidystonia. Focal means that one body part is affected and includes conditions such as blepharospasm, oromandibular dystonia, adductor spasmodic dysphonia, spasmodic torticollis, and writer's cramp. Segmental implies two or more contiguous regions such as involvement of a whole limb with the associated part of the trunk. Hemidystonia denotes one side of the body.

Hereditary childhood onset dystonia (idiopathic torsion dystonia, DYT1) most commonly starts between 6 and 12 years of age with dystonia of the foot while walking. The illness is then slowly progressive and becomes generalized. The disorder is usually autosomal dominant with reduced penetrance both in Jews and nonJews (Bressman et al., 1994a).