Friday, January 22, 2010

Dystonia: A brief descriotion

Dystonia is a syndrome of sustained muscle contractions that produce twisting and repetitive movements or abnormal postures. The extent and severity of muscle involvement are remarkably variable, ranging from intermittent contraction limited to a single body region to a more generalised dystonia, involving the limbs and axial muscles.
  • According to the body regions affected, dystonia is described as focal if a single area is involved, such as (1) the face, (2) oromandibular area, (3) arm, or (4) neck.
  • It is described as segmental if 2 or more contiguous areas are affected, such as (1) cranial and cervical areas or (2) the face, jaw, and tongue.
  • It is multifocal if 2 or more noncontiguous body regions are involved, such as (1) an arm and a leg with cranial muscle involvement or (2) blepharospasm and leg dystonia. Finally, it is generalised if both legs and 1 other body region are involved.

Many dystonic movements are action-specific. Some individuals develop involuntary movements only during writing (eg, writer's cramp), while others may have dystonic movements in the arm and trunk when walking but not when dancing.

Many patients with dystonia can partially control their arms using small tactile maneuvres, such as touching the chin in the case of cervical dystonia or touching the brow in the case of blepharospasm (geste antagonistique). These tactile maneuvres may mislead physicians to the erroneous diagnosis of malingering or hysteria.

In 1911, Oppenheim introduced the term dystonia to describe the variable tone present in patients with abnormal muscle spasms. Persistent dystonia was introduced by the French to describe the late complications of chlorpromazine therapy.

Keegan and Rajput
In 1973, Keegan and Rajput introduced the term dystonia tarda to describe drug-induced sustained muscle spasm causing repetitive movements or abnormal postures in patients who were treated with levodopa.

In 1982, Burke coined the term tardive dystonia; tardive derives from the Latin word meaning late onset. They proposed the following 4 criteria for diagnosis:

  1. The presence of chronic dystonia
  2. A history of antipsychotic drug treatment preceding or concurrent with the onset of dystonia
  3. The exclusion of known causes of secondary dystonia by appropriate clinical and laboratory evaluation
  4. A negative family history of dystonia

A fifth criterion was also proposed but appeared to gain little acceptance from other researchers — "If other involuntary movements (such as dyskinesia, akathisia) are additionally present, the dystonia is the most prominent."

Tardive Dystonia
Traditionally, tardive dystonia is considered an extremely disabling subtype of a broader syndrome known as tardive dyskinesia. The original descriptions of tardive dyskinesia referred to stereotyped orolingual and masticatory movement of a choreic nature, taking the form of lip smacking and pursing, tongue protrusion, and licking and chewing movements.

This term should only be used for those movement disorders developing after long-term exposure to dopamine receptor–blocking agents, However, this traditional view has come under attack in recent years, as some argue these should be characterised as 2 separate disorders.

Further information on Dystonia and related topics available here ...........

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