Myoclonic dystonia, a genetic form of dystonia, is characterized by rapid jerking movements alone or in combination with the sustained muscular contractions and postures of dystonia.
Terms used to describe myoclonic dystonia include: myoclonus dystonia, inherited myoclonus-dystonia syndrome, DYT11 dystonia
Note: Some researchers believe myoclonic dystonia is a variation of hereditary essential myoclonus.
Myoclonus is a movement dystonia characterized by sudden, brief, shock-like movements. Individuals with myoclonic dystonia exhibit symptoms of dystonia plus very prominent myoclonic movements. The distribution of these rapid "jerks" is variable but most frequently affects the central part of the body, including the shoulders, arms, neck, and trunk. Rarely are the face and legs affected. (The symptom distribution of myoclonic dystonia is different from typical early onset generalized dystonia as it more often affects the upper body whereas typical early-onset dystonia usually affects the legs.) Symptoms may be impacted by the consumption of alcohol. Non-movement related features may be present including depression, anxiety, obsessive-compulsive disorder, personality disorders, and panic attacks. The age of onset is in the first or second decade of life, although some cases of adult-onset have been reported. Most frequently, the disorder appears to be slowly progressive for a few years after onset, stabilizes, and then fluctuates slightly over the years or shows a mild spontaneous improvement.
Myoclonic dystonia is often a familial disorder seen in successive generations. Scientists have uncovered that multiple mutations in the epsilon-sarcoglycan gene associated with this form. The function of this gene is still unknown. This disorder is inherited dominantly but only a percentage of individuals who inherit the mutation develop symptoms.
Sporadic cases may arise, but it is unclear at this time if these cases are actually genetic in which the family history is "masked" by reduced penetrance.
Diagnosis of myoclonic dystonia is based on family history from the affected individual and the physical and neurological examination.
If the condition presents with both myoclonus and dystonia, it may be classified as "myoclonic dystonia" or "hereditary dystonia with lightning jerks responsive to alcohol." If dystonia is not present or is only a minor component, it may be classified as "hereditary essential myoclonus." Experts in the movement disorder field are aware of the different diagnoses, and debate continues as to whether all classifications may be an expression of a single genetic disorder.
Medications that may be helpful for the treatment of myoclonic dystonia include benztropine, clonazepam, neuroleptics, dopamine agonists, and perhaps gamma-hydroxybutyrate (GHB). A striking feature in some people with myoclonic dystonia is the alleviation of symptoms upon ingestion of alcohol, but response varies greatly even within individual families. Deep brain stimulation surgery is emerging as a promising option.
Complementary therapies may be explored, especially physical therapy, aquatic physical therapy, and regular relaxation practices.