Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. Dystonic movements are typically patterned, twisting, and may be tremulous. Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation1

Women are affected by dystonia about twice as often as men.  Although the genetic causes of dystonia, especially for adult-onset focal forms, are still largely elusive, a positive family history is found in about 20% of dystonia sufferers2.

The use of the term intermittent is included in the definition because there is a common misconception that dystonic movements are always sustained, slow, or twisting3. Since the diagnosis of dystonia is based on clinical observation and there are no supportive laboratory measures2, clinical recognition is more difficulty when dystonic movements occur in isolation, and these movements may include:

The current definition emphasises that dystonic movements tend to be patterned, and that dystonia characteristically worsens with voluntary action. Some of the most important features of dystonia, that distinguish it from other hyperkinetic disorders, are the relationship to movement and posture, and the stereotyped or patterned character of the movements1.  Some forms of dystonia, such as blepharospasm and laryngeal dystonia, are not associated with postures, but are limited to focal involuntary contractions.

Dystonia is potentially made up of:

  1. A tonic component, that is, dystonic postures, and
  2. A phasic component, that is, dystonic movements.

Current classifications of dystonia take the approach of reviewing the clinical features, and then using these, subsequently to determine the syndromic pattern3:

Recognition of the phenomenology of dystonia and of the prevalent syndromic pattern.

From: Jinnah HA, Albanese A. The New Classification System for the Dystonias: Why Was It Needed and How Was It Developed? Mov Disord Clin Pract. 2014;1(4):280-284. doi:10.1002/mdc3.12100