A type of involuntary movement characterised by a sustained muscle contraction, frequently causing twisting and repetitive movements or abnormal postures, and caused by inappropriate instructions from the brain. It is sometimes called torsion spasm, and may be synonymous with ATHETOSIS, when the extremities are involved. Often the condition is IDIOPATHIC but there may be an inherited predisposition in some people. Others may have brain disorders such as CEREBRAL PALSY or WILSON'S DISEASE.

The presentation may be focal (usually in adults) causing blepharospasm (forceful eye closure); oromandibular dystonia (spasms of the tongue and jaw); cranial dystonia/Meige syndrome/Brueghel's syndrome (eyes and jaw both involved); spastic or spasmodic dysphonia/laryngeal dystonia (strained or whispering speech); spasmodic dysphagia (difficulty swallowing); spasmodic torti/latero/ante/retrocollis (rotation, sideways, forward or backward tilting of the neck); dystonic writer's cramp; or axial dystonia (spasms deviating the torso). Foot dystonia occurs almost exclusively in children and adolescents. In adults, the condition usually remains focal or involves, at most, an adjacent body part. In children, it may spread to become generalised. The condition has always been considered rare, but commonly is either not diagnosed or mistakenly thought to be of psychological origin. It may, in fact, be half as common as MULTIPLE SCLEROSIS (MS). Similar features can occur in some subjects treated with major tranquillising drugs, in whom a predisposition to develop dystonia may be present.

One rare form, called dopa-responsive dystonia, can be largely abolished by treatment with LEVODOPA. Particularly in paediatric practice this drug will often be tried on a child with dystonia.