The exact triggers of dystonia are not entirely known. However, researchers believe it can develop from genetic mutations, as a side effect of medications or as a symptom of another disease.
Dystonia may be inherited as in cases of several syndromes or acquired as a result of environmental, infectious or disease-related brain damage. Certain types of dystonia may be seen as a side effect of medications.
Damage to the nervous system, especially to the part of the brain called the basal ganglia, may cause loss of coordinated movements in various muscle groups. This causes the muscles to uncontrollably twist or experience repetitive movements or irregular body positions called dystonic movements.
In some cases of dystonia, there is no specific cause. Cases occur randomly for no apparent reason, without a family history of the disorder (sporadically). In many cases, the exact underlying cause of dystonia remains unproven (idiopathic).
- Multiple genes have been associated with inherited dystonia and researchers are actively seeking to locate additional gene and gene markers.
- Genetic factors are also believed to play a role in idiopathic and acquired dystonia, especially in individuals who have a relative with another form of the condition.
- These individuals may have a genetic susceptibility to developing the disorder.
- A person who is genetically predisposed to a disorder carries a gene (or genes) for the disease, but the gene may not be expressed unless it is triggered or activated by other genetic modifiers or environmental factors (complex genetics).
In some cases, dystonia occurs due to a known specific cause (acquired dystonia). Conditions associated with acquired dystonia include:
- Brain injury (particularly due to lack of oxygen) during or around the time of birth (the perinatal period) or carbon monoxide poisoning
- Certain infections such as tuberculosis, measles or herpes simplex encephalitis
- Reactions to heavy metal poisoning
- Certain medications including caffeine and some antiepileptic, antipsychotics, antidepressants, anti-emetics, antihistamines, amphetamines and oral contraceptives
- Various vascular abnormalities such as stroke, malformations or hemorrhaging (profuse, excessive bleeding)
Moreover, dystonia can result from other illnesses affecting the central nervous system (Huntington’s disease, Parkinson’s disease or Wilson’s disease).
Other risk factors are as follows:
- Age: Although the disorder can occur in people of any age, it most commonly begins after 30 years of age.
- Sex: Women are more likely to develop cervical dystonia than men.
Scientists have not yet identified the precise biochemical process in the body that triggers symptoms. Research is ongoing to determine the specific roles that genetic, environmental and other factors ultimately play in the development of the disorder. Recent developments show that inheriting the mutated DYT1 gene may increase a child’s risk of dystonia. Other genetic mutations may also be associated with dystonia.
What is dystonia?
Dystonia is the presence of abnormal (often painful) body movements that may involve either a specific part of the body (hands, head and lower limb) or the entire body. Dystonic movements are often patterned and can range from mild to severe muscle contractions.
Dystonia results from a functional or structural alteration in the brain cell circuits of the central nervous system. It can affect different regions of the body, including the face, eyelids, jaw, neck, vocal cords, torso, hands, arms, feet or legs.
The main symptom of dystonia is muscle overactivation leading to muscle contraction. Symptoms often go through stages, though at first, they appear during voluntary movements or under physical or emotional stress. This can escalate to dystonic postures or involuntary movements while walking or being relaxed.
Other signs of dystonia include:
- Involuntary muscle contraction that occurs only during attempts at movement
- Muscle contraction only during a specific task
- Involuntary twisting of the neck, movement in an arm or leg or blinking
- Slurred speech or difficulty swallowing
- Voice tremors
- Body part becoming fixed in an abnormal position and being unable to move it
- Repetitive body posturing including arching of the neck or back
- Movements are sometimes temporarily relieved by touch or action
- Voluntary movement on one side of the body triggers involuntary movement on the opposite side
How is dystonia treated?
Currently, there is no curative treatment for dystonia. Doctors may recommend personalized treatment according to its intensity, location and interference with the person’s activity.
Treatment for dystonia may include:
- In general, they provide limited improvement.
- The most used medications are clonazepam, tetrabenazine, anticholinergics and some neuroleptics.
- Local infiltration with botulinum toxin of the involved muscles is the treatment of choice in severe cases of dystonia.
- It has shown excellent results with minimal side effects.
- Infiltrations must be repeated every three to four months. In some cases, loss of efficacy may develop due to the development of neutralizing antibodies.
- Performed using deep cerebral stimulation with electrodes implanted in the internal pale balloon.
- The treatment of choice in generalized dystonia, as well as in cervical dystonia, does not respond to infiltration with botulinum toxin and dystonia secondary to drugs.