Dystonia is a movement disorder characterized by involuntary muscle contractions or spasms, frequently causing twisting and other movements or abnormal postures.
Dystonia is classified by age of onset, by the parts of the body affected, and by cause. It can be divided into focal and generalized dystonia. Generalized dystonia affects several areas of the body whereas focal dystonia is limited to one area.
Commonly described forms of focal dystonia include:
- Cervical dystonia (spasmodic torticollis)
- Blepharospasm (dystonia of the eye muscles)
- Oromandibular dystonia (dystonia of mouth muscles and jaw)
- Laryngeal dystonia (spasmodic dysphonia)
- Limb dystonia (dystonia of an extremity, such as writer’s cramp)
Primary dystonia is thought to be caused by a pathology of the central nervous system, likely originating in the basal ganglia area of the brain that regulates movement.
Secondary dystonia can be due to other causes, including medications, stroke, trauma, or birth injury. Some types of dystonia are inheritable.