July 18, 2009

Task-specific Dystonia in Sports

My interest in this subject was piqued by a video of Charles Barkley's golf swing.

There are plenty of other examples on Youtube of the same swing. This is a severe example of what in golf is called the yips. It doesn't have any connection to this restaurant that I am aware of.

By Mayo Clinic staff

Yips are involuntary wrist spasms that occur most commonly when golfers are trying to putt. However, the yips can also affect people who play other sports — such as cricket, darts and baseball.

It was once thought that the yips were a form of performance anxiety. However, it now appears that the yips are an example of focal dystonia, which is a neurological dysfunction affecting specific muscles.

Some people have found relief from the yips by changing the way they perform the affected task. For example, a right-handed golfer might try putting left-handed.

Worsening with anxiety is a classic symptom of dystonia, so the yips are probably more often dystonic movements than this definition states. The yips have been discussed as a dystonia in a Japanese scientific article.(1)

Dystonia is a movement disorder characterized by involuntary, directional (sometimes twisting), stereotyped movements. They are often sustained (longer than a tic) but can be brief. They involve simultaneous contraction of the agonist and antagonist muscles. The movements are frequently worsened with action, thus called action dystonias. Some action dystonias only occur with specific tasks. The most common task specific dystonia is writer's cramp. Task specific dystonias have been described for auctioneering, playing the piano, and playing a wind or brass instruments with abnormal movements of the tongue, lip, and chin muscles.

A free throw dystonia appears to affect Chuck Hayes. The commentators are not very forgiving.The same problem with release can occur in darts, referred to as dartitis. It has been considered a psychologic problem but it is certainly a neurologic one. Here's a severe example.

There is a body of literature regarding musician's dystonias but less about sports dystonias. One paper describes freezing of the arm in shoulder flexion during boule throwing.(1) The Abstract from the article:
During a period of intensive practice, 2 petanque players developed freezing of shoulder flexion impeding boule throwing. This movement disorder was consistent with the diagnosis of task-specific focal dystonia. Polymyography showed that freezing was associated with bursts of low amplitude. In the absence of motor or sensory deficits, a motor apraxia could be considered.

In an animal model of focal dystonia, produced by inducing overusage of a limb, areas of sensorimotor cortex responsible for the particular movement were 10-20 times larger. From this data, it has been suggested that there is decreased inhibition in the cerebral cortex of those with dystonia. Functional imaging studies have shown increased blood flow in the premotor cortex and supplementary area. There may be decreased inhibition of the thalamus by the globus pallidus interna.

Certainly the repetitive movements of musicians or athletes alter topographic representations of motor and sensory fields on the cortex. This remapping somehow interferes with normal inhibitory influences and some individuals are more prone to this than others. Treatment options for sports associated dystonias include, sensory retraining with practiced repetitive stimulation such as Braille, use of sensory tricks, or Botox. None of these have been tried or tested rigrously. Diagnosis could include functional imaging modalities that measure sensorimotor areas in the cortex.

The idea that the cortex is altered by activity is hardly a new one. How much of a role this plays in dystonia is not entirely clear, but task-specific dystonias seem to suggest that in some susceptible individuals, repeated usage results in maladaptive cortical reorganization. And maybe, Barkley's case of the yips, atypical for its proximal muscle involvement, may in part result from his repeated foul throw shooting earlier in life.

1.Tanaka M, Ohyagi Y, Kawajiri M, Taniwaki T, Tobimatsu S, Furuya H, Yoshiura T, Kira J. A patient with focal dystonia induced by golf and presenting a decrease in activity of cerebral motor cortex on task. Article in Japanese. Rinsho Shinkeigaku. 2005 Apr;45(4):304-7.

2. Lagueny A, Burbaud P, Dubos JL, le Masson G, Guelh D, Macia F, Debras C, Tison F. Freezing of shoulder flexion impeding boule throwing: A form of task-specific focal dystonia in petanque players. Movement Disorders 2002;17:1092-5.

1 comment:

Blognut said...

I can't stop watching dartitis even though it makes me really uncomfortable.