Focal hand and limb dystonia usually manifests as a painless loss of muscular control in highly practiced movements. A genetic predisposition is surmised in less than 5% of all cases of focal dystonia.

Symptoms
 

Most affected musicians describe symptoms in musical terms. A musician may notice:
• Subtle loss of control in fast passages
• Lack of precision
• Curling of fingers
• Fingers "sticking" to keys
• Involuntary flexion of bowing thumb in strings
A tremor may or may not be associated with the spasms.

In most cases, the dystonia is present only in the context of specific tasks. For example, some woodwind doublers report the dystonia may be present while playing the clarinet but not while playing the saxophone.

The dystonia may appear extremely sensitive to sensory input: a pianist may experience symptoms while playing on ivory keys but not while playing on plastic keys. Sometimes the modification of posture and even facial expressions may affect dystonic spasms in the hand.

Cause

There is no one isolated cause of hand and limb dystonia. A variety of pathological conditions may lead to similar symptoms. As a child develops, he/she learns many different movements (such as walking, writing, or playing an instrument) that are stored in the brain as motor programs. Instances of hand dystonia that are highly task-specific have been described as a "computer virus" or "hard drive crash" in the sensory motor programs that are essential for playing music. However, additional factors, such as a genetic predisposition, are likely to play a significant role in the development of such a sensory-motor dysfunction. Why this "computer virus" cannot be easily overcome by establishing a new and improved sensory-movement pattern remains an important question for researchers.

In a small group of musicians affected by dystonia, the hand cramps may be related to other dystonias. Symptoms may develop following the onset of writer's cramp or may be an initial manifestation of segmental or generalized dystonias.

Treatment
 

There is no cure for dystonia at this time, and although treatment of the disorder may be challenging, there are several available options.

Anticholinergic drugs, such as Artane ® (trihexyphenidyl), can be helpful in treating focal dystonias by affecting the transmission of messages from the brain to the muscles.

Botulinum toxin injections may be used to compel the body to create new programs by blocking the nerve impulses to the contracting muscles. The injections temporarily weaken the muscle so that the spasm is reduced and a different wrist position is necessary to compensate for the relaxed muscle. In this case, the injection itself is not the solution but rather a tool to facilitate the musician developing a modified motor program.

The ultimate aim of treatment is to establish new sensory motor programs to accomplish the tasks required for playing music. It might be possible to modify the instrument.

Sources Dysonia medical research foundation