Focal dystonias are adult-onset forms that affects a specific area of the body. (Dystonia-Foundation.org)
Most focal dystonias are primary (meaning that it is the only neurological symptom and presumed to have a genetic component), though secondary cases are documented. Focal dystonia may affect muscles of the eyes, mouth, vocal cords, neck, hands, and feet. Types of focal dystonia include:
Blepharospasm—Affects the eyes
Cervical dystonia (spasmodic torticollis)—Affects neck and shoulders
Laryngeal dystonia (spasmodic dysphonia)—Affects the vocal cords
Hand dystonia (writer’s cramp)—Affects the hands and forearm
The dystonias are movement disorders in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The movements, which are involuntary and sometimes painful, may affect a single muscle; a group of muscles such as those in the arms, legs, or neck; or the entire body. Those with dystonia usually have normal intelligence and no associated psychiatric disorders.
(National Institute of Neurological Disorders and Stroke)
What are the symptoms?
Dystonia can affect many different parts of the body. Early symptoms may include a deterioration in handwriting after writing several lines, foot cramps, and/or a tendency of one foot to pull up or drag; this may occur "out of the blue" or may occur after running or walking some distance. The neck may turn or pull involuntarily, especially when the patient is tired or stressed. Sometimes both eyes will blink rapidly and uncontrollably, rendering a person functionally blind. Other possible symptoms are tremor and voice or speech difficulties. The initial symptoms can be very mild and may be noticeable only after prolonged exertion, stress, or fatigue. Over a period of time, the symptoms may become more noticeable and widespread and be unrelenting; sometimes, however, there is little or no progression.
How are the dystonias classified?
One way to classify the dystonias is according to the parts of the body they affect:
Generalized dystonia affects most or all of the body.