Dystonias are disorders characterized by muscle spasms and contractions. Dystonia is thought to be neurological in origin, but the condition does not affect people’s intelligence, memory or language ability. If the dystonia is genetic or the cause is unknown, it is termed primary dystonia, while dystonia that occurs due to an underlying disease such as stroke, encephalitis, Parkinson’s disease or head injury, is referred to as secondary dystonia.
The pathology behind primary dystonia is generally thought to involve the basal ganglia in the brain. The basal ganglia is made up of a group of cells that influence parts of the brain that are responsible for muscle control.
Several forms of primary dystonia have been linked to genetic mutations and include dopa-responsive dystonia, generalised dystonia and paroxysmal dystonia. The faulty genes are inherited in an autosomal dominant fashion, which means a child born to a parent who carries one of the mutaitons has a 50% chance of inheriting the gene and developing dystonia.
Also known as acquired dystonia, secondary dystonias are usually caused by another condition, some of which are described below.