Researchers suspect it is caused by a pathology of the central nervous system, likely originating in those parts of the brain concerned with motor function—such as the basal ganglia and the GABA (gamma-aminobutyric acid) producing Purkinje neurons. The precise cause of primary dystonia is unknown. In many cases it may involve some genetic predisposition towards the disorder combined with environmental conditions.Secondary dystonia refers to dystonia brought on by some identified cause, such as head injury, drug side effect (e.g. tardive dystonia), or neurological disease (e.g. Wilsons disease, stroke).Meningitis and encephalitis caused by viral, bacterial, and fungal infections of the brain have been associated with dystonia. The main mechanism is inflammation of the blood vessels, causing restriction of blood flow to the basal ganglia. Other mechanisms include direct nerve injury by the organism or a toxin, or autoimmune mechanisms.Environmental and task-related factors are suspected to trigger the development of focal dystonias because they appear disproportionately in individuals who perform high precision hand movements such as musicians, engineers, architects, and artists. Chlorpromazine can also cause dystonia, which can be often misjudged as a seizure.Neuroleptic drugs often cause dystonia, including oculogyric crisis.Malfunction of the sodium-potassium pump may be a factor in some dystonias. The Na+-K+ pump has been shown to control and set the intrinsic activity mode of cerebellar Purkinje neurons. This suggests that the pump might not simply be a homeostatic, "housekeeping" molecule for ionic gradients; but could be a computational element in the cerebellum and the brain.
Multifocal dystonia affects many different parts of the body. Generalized dystonia affects most of the body, frequently involving the legs and back. Genetic/primary
There is a group called myoclonic dystonia where some cases are hereditary and have been associated with a missense mutation in the dopamine-D2 receptor. Some of these cases have responded well to alcohol.Other genes that have been associated with dystonia include CIZ1, GNAL, ATP1A3, and PRRT2. Another report has linked THAP1 and SLC20A2 to dystonia. Signs and symptoms
Symptoms vary according to the kind of dystonia involved. In most cases, dystonia tends to lead to abnormal posturing, in particular on movement. Many individuals with the condition have continuous pain, cramping, and relentless muscle spasms due to involuntary muscle movements. Other motor symptoms are possible including lip smacking.Early symptoms may include loss of precision muscle coordination (sometimes first manifested in declining penmanship, frequent small injuries to the hands, and dropped items), cramping pain with sustained use, and trembling. Significant muscle pain and cramping may result from very minor exertions like holding a book and turning pages. It may become difficult to find a comfortable position for arms and legs with even the minor exertions associated with holding arms crossed causing significant pain similar to restless leg syndrome. Affected persons may notice trembling in the diaphragm while breathing, or the need to place hands in pockets, under legs while sitting or under pillows while sleeping to keep them still and to reduce pain.