What is Dystonia?

Dystonia is a neurologic movement disorder characterized 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.

Classification of Dystonia

Dystonia is classified in a number of ways including...

• Age at which symptoms appear. Symptoms may become apparent during childhood, adolescence, or adulthood.
• Area or areas of the body that are affected. Sustained muscle contractions and abnormal movement patterns may be limited to one area of the body; involve two or more areas of the body that are next to each other, as in segmental dystonia or two or more areas of the body that are not next to each other (non-segmental or multi-focal); or be generalized in nature, including leg involvement and other areas of the body.
• Cause. 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 characterized by neurologic features, such as parkinsonism or myoclonus. Dystonia is also a primary feature of certain, usually hereditary, neurodegenerative disorders (so-called "heredodegenerative dystonias").

Dystonia and its Relationship to Activity

Dystonic movements or posturing are often described as they relate to activity or factors that may aggravate symptoms.

• Dystonia, particularly primary dystonia, of a body part may...
• Occur only during voluntary movement or become worse during these movements. This is known as action dystonia. Dystonia that appears only with specific actions, such as writing (i.e., "writer's cramp"), is a task-specific dystonia. Primary dystonias often begin as task-specific yet eventually appear with other activities as the condition progresses. For example, dystonic cramping and spasms that initially appear only when writing may eventually occur during other activities, such as eating.
• Occur with voluntary movements of other, unaffected bodily regions. This phenomenon, known as "overflow," may develop as a dystonic condition progresses.

Occur even when the affected body part is at rest. This is referred to as rest dystonia. Rest dystonia may develop with further progression of a dystonic condition and therefore is typically considered more severe than action dystonia.

Lead to sustained, abnormal, fixed postures or positions of affected body regions, potentially causing permanent contractures.

Dystonic contractions are relatively slow or rapid in speed, sometimes resembling other neurologic movement disorders, such as the "shock-like" muscle contractions seen in myoclonus or the irregular, relatively brief movements of chorea. Dystonic movements are more closely associated with prolonged bursts of electrical activity in affected muscle(s) rather than the short, irregular bursts of myoclonus. In addition, dystonic movements tend to have a sustained, directional nature rather than the random, flowing contractions seen with chorea. Dystonia also typically may be distinguished from the involuntary, rhythmic, "back-and-forth" movement characteristic of tremor. In some dystonic patients, tremor-like muscle spasms or tremulous movements or dystonic tremor may be present upon attempting to actively resist abnormal, involuntary movements.

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.