Focal forms of dystonia are usually limited to one area of the body. Most cases of focal dystonia appear later in life and are referred to as adult-onset.
The symptoms associated with the focal dystonias are variable and depend upon the intensity and severity of the spasms and the specific body region and muscle groups involved. The rate of progression from symptom onset to difficulties in activities of daily living and disability are extremely variable, ranging from rapid development over days or weeks to a gradual progression over a decade or more.
Symptoms of focal dystonias may initially be periodic, occurring only during stressful periods or randomly. At first, symptoms tend to appear when the affected body part performs certain movements; they typically disappear when the affected area is at rest. In some cases, the symptoms of dystonia may extend to involve nearby areas, resulting in segmental dystonia. Less commonly, symptoms may begin to affect certain non-adjacent regions (multifocal dystonia).
Focal dystonias often stabilize within a few years and may gradually slightly improve. In addition, some patients may experience a temporary diminishing or complete remission of symptoms for days or months, usually within 2 to 3 years following disease onset. Evidence suggests that remissions most frequently occur in patients with cervical dystonia, as compared with other focal dystonias.