Dystonia

Dystonia is the term used to describe a condition dominated by involuntary sustained muscle spasms which can be extremely painful. These can affect various parts of the body and cause abnormal movements and postures.

The condition is due to malfunction of the central nervous system, probably in those parts of the brain called the basal ganglia. In primary dystonia no other functions of the brain are involved and investigations reveal no identifiable cause. In a minority of cases, specialised tests can identify known causes that damage the basal ganglia, and the dystonia in these cases is called ‘secondary’ or ‘symptomatic’.

Dystonia is best classified according to the parts of the body affected. If only one part of the body is affected, such as the eyes, neck or a limb, it is called focal dystonia. If a larger region such as the neck and arms is involved, it is called segmental dystonia. If the spasms affect the arm and leg on the same side, it is known as hemidystonia. If the dystonia is more widespread, the term ‘generalised dystonia’ is used. Dystonia is a neurologic movement disorder characterised by sustained muscle contractions, usually producing twisting and repetitive movements or abnormal postures or positions. Almost all dystonic movements share a directional quality that is typically sustained, sometimes for an instant, as well as a consistency and predictability Dystonia movements are directional, forcing the involved body part or region into an abnormal position, which is consistently present.

Dystonia may occur as a primary condition (idiopathic dystonia) that is familial or occurs in the absence of a family history. It may result from certain environmental factors or “insults” that affect the brain (secondary or symptomatic dystonia). Dystonia may be associated with certain nondegenerative, neurochemical disorders (known as “dystonia-plus syndromes”) that are characterised by neurologic features, such as parkinsonism or myoclonus.

Dystonic spasms typically increase in intensity during stress, emotional upset, or fatigue. Spasms tend to decrease in intensity during periods of rest or sleep. Many patients temporarily suppress dystonic movements or spasms by “sensory tricks.” These tricks usually consist of touching the affected or adjacent body parts. Also known as gestes antagonistes, these sensory tricks are a phenomenon almost unique to dystonia; therefore, they may play a helpful role in differential diagnosis.

 The Dystonia Society