Dystonia
Background
Dystonia is a term for a group of neurological disorders in which involuntary muscle spasm leads to abnormal movements and postures. These postures tend to change from moment to moment especially during attempts to carry out a movement and may be most evident during walking or performing specific tasks. The dystonias are one of several movement disorders caused by impaired or altered function in large groups of nerve cells in the centre of the brain called the basal ganglia.
Dystonia can be classified as primary or secondary. Dystonia can also be classified by how much of the body is involved. Focal dystonia affects one body part such as the neck in spasmodic torticollis or cervical dystonia, or the eyes in blepharospasm. More severe dystonia can be described as segmental if it involves two adjacent body parts, for example the neck and an arm, and if the legs and trunk are also affected it is described as generalised. In general, the more severe forms of dystonia have onset in childhood whilst focal dystonia is a condition with onset in adulthood.