Patients with focal dystonia have involuntary muscle contractions that can be painful in a single group of muscles. In comparison, patients with generalized dystonia have these muscle contractions that affect either most or all of their body.
There are several types of focal dystonia, which differ by the muscle group affected. One type of focal dystonia is focal dystonia of the hand, which is also called “writer’s cramp” or “pianist’s cramp,” as it affects people who perform repetitive hand movements. The Dystonia Medical Research Foundation noted that focal hand dystonia accounts for 5 percent of all focal dystonia cases.
The NYU Langone Medical Center stated that a dystonia can occur when dysfunction occurs in an area of the brain called the basal ganglia. This dysfunction affects proper signaling for muscle contractions. Inherited abnormalities may cause this dysfunction, as well as acquired conditions, such as a stroke, trauma, infection, vitamin B-12 deficiency or a reaction to medication.
With focal hand dystonia, there is not an identified specific cause. The Dystonia Medical Research Foundation noted that “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.”
In some cases of focal dystonia of the hand, patients may develop generalized dystonia or segmental dystonia, in which two or more adjacent body parts are affected.
Patients with focal hand dystonia may have curling of their fingers and a lack of precision. Musicians with this type of dystonia may have a subtle loss of control when playing pieces with faster parts or feel like their fingers are sticking to the keys. Many focal hand dystonia patients only have symptoms when performing certain tasks, according to the Dystonia Medical Research Foundation.
Some patients may experience tremors with the muscle spasms. Non-musicians with focal dystonia of the hand may have trouble writing — their handwriting becomes worse after they write a few lines.
While there is no cure for focal hand dystonia, several treatments are available.