Myoclonus is the term used to describe brief ‘lightning-like’ jerks by the body. The term is the description of a symptom not an underlying condition and myoclonus has a number of different causes. For instance, many people may occasionally experience a myoclonic jerk when falling asleep.
Sometimes myoclonic jerks occur in combination with dystonia, a neurological condition where incorrect signals between the brain and the muscles result in unwanted muscle activity. Where this happens, the condition is called myoclonus-dystonia (M-D). The movements generally occur in the arms, trunk and neck. The myoclonic jerks are diagnosed as M-D where they are accompanied by other symptoms of dystonia (which happens in around 50% of cases) and/or where the person affected has a faulty version of the SGCE gene (see next section).
M-D symptoms generally start at a young age, often within either the first or second decade of life.
Many cases of M-D are inherited and result from a mutated (faulty) version of the SGCE gene (also sometimes referred to as DYT11 in the classification of dystonia genes). However, this does not mean that M-D will necessarily be passed on to children. The SGCE gene is inherited in an autosomal dominant manner: which means that there is a 50% chance that a child will inherit the mutation if one parent has it.
Even if a child inherits the SGCE mutation this does not mean they will develop M-D as the SGCE gene undergoes a process called ‘maternal imprinting’. This means that if the faulty gene is inherited from the mother it is effectively switched off and the disorder is highly unlikely to be inherited by her children. However, it is possible that, where her male children inherit the gene and pass it to their child, the gene may be switched on again so the condition may develop in her grandchildren (there is a 50% chance that the son inherits the gene and if he does so then, for each of his children, a 50% chance that he will pass the gene on to them).
There are also a number of families with M-D but no SGCE mutation, suggesting that there may be other genes that can cause this disorder and that more research needs to be done.
Sometimes a single case of M-D appears although no-one else in the family is affected (this is called a sporadic case). As sporadic cases of M-D have similar symptoms to familial cases it is possible that, even if the DYT11 mutation is not present, many of these will also have a genetic cause that has not yet been identified.
The involuntary movements can be triggered or worsened by active movements of the affected parts of the body and also by stress and anxiety.
M-D may also be accompanied by psychological symptoms such as obsessive-compulsive disorder (OCD) where unwanted thoughts, urges and repetitive activities become an obstacle to living life as you want to. M-D may also cause anxiety or lowered mood (depression). It should be noted that these psychological impacts are more likely if the M-D is caused by a mutation within the DYT11 (SGCE) gene.
The jerking movements may improve when alcohol is taken but this does increase the risk of alcohol abuse and consequent resulting long-term health effects.
Management of M-D
Treatment of physical symptoms
The need for treatment depends on the severity of the symptoms – some people find they can cope without treatment. For those whose symptoms are more severe, treatment usually involves a combination of medications as one single agent can seldom completely control myoclonus. Drugs which are sometimes used include antiepileptic drugs and anticholinergic medication (trihexyphenidyl). Although these medications can be very helpful, they are not universally effective, and some patients experience side effects.
Botulinum toxin injections can be used to treat the dystonia, particularly if it affects the neck. These treatments may sometimes reduce the severity of the myoclonus as well. The injected botulinum toxin temporarily relaxes the muscles at the site of the injection, and the injections are usually repeated every three months or so. Many patients find these injections to be a successful treatment, with generally rare and mild side effects.
Deep brain stimulation (DBS) is an option available if symptoms are severe and all other treatments are failing to control the symptoms. DBS is a surgical procedure in which two fine electrodes are inserted into the brain. They are connected to a battery implanted under the skin which delivers a constant, painless, signal which blocks the signals that cause the disabling symptoms of myoclonus dystonia
As some kinds of M-D are associated with psychological problems, it may also be necessary to seek specific help. Anti-depressant medications (or anxiolytics) are helpful in the treatment of depression or anxiety but others may find talking-based therapies are also helpful.
Talking therapies provide a regular time and opportunity to talk about your troubles and explore difficult feelings with a trained professional. This can help deal with specific conditions, cope with a crisis, improve relationships, or develop better ways of living. The purpose of talking therapies is not, usually, to give advice, but to help you understand your feelings and behaviour better and, to help you change your behaviour or the way you think about things. There are a number of different types of talking treatments including cognitive behavioural therapy (CBT), counselling and psychotherapy.
You may find it helpful to speak to a genetic counselor about the genetic issues and the implications this may have on other family members developing M-D.
To read case studies of individuals with myoclonus dystonia that have been featured in Dystoniamatters! click on the links below:
Last reviewed August 2014
The Dystonia Society provides the information on this page as general information only. It is not intended to provide instruction and you should not rely on this information to determine diagnosis, prognosis or a course of treatment. It should not be used in place of a professional consultation with a doctor.
The Dystonia Society is not responsible for the consequences of your decisions resulting from the use of this information, including, but not limited to, your choosing to seek or not to seek professional medical care, or from choosing or not choosing specific treatment based on the information. You should not disregard the advice of your physician or other qualified health care provider because of any information you receive from us. If you have any health care questions, please consult the relevant medical practitioner.