What is focal dystonia?
Focal dystonia is a disorder of the nervous system, characterised by involuntary muscle contractions and resulting in changes in posture. The term "focal" means that the muscle with dystonia is at a localised location on the body.
Focal dystonia can occur in adulthood but also in children and adolescents. It affects both men and women equally.
The different types of focal dystonia
There are 7 types of focal dystonia, including:
- Cervical dystonia or spastic torticoli: this dystonia is located in the neck and/or shoulders. It is the most common type of focal dystonia in adults.
- Blepharospasm: it is located in the eyelid and eyebrow muscles.
- Oral-maudibular or cranial dystonia: it causes spasms of the face, jaw or tongue. It is often associated with blepharospasm.
- Spastic dystonia: This type of dystonia targets the vocal cords.
- Hand dystonia: This type affects the wrist, hand or fingers.
- Lower limb dystonia: it affects the toes, foot or leg.
- Function dystonia: this type of dystonia occurs when a specific movement is performed, such as writing or playing an instrument.
The causes of dystonia
There are two main types of dystonia forms.
- Dystonia without known origin: This type of dystonia occurs in a person whose family member does not have dystonia.
- Dystonia of genetic origin: the patient is a carrier of a defective gene (part of the chromosome). Usually other members of the family are also affected. Some chromosomes and chromosome parts have already been identified: DYT6 part of chromosome 8, DYT7 part of chromosome 18 and DYT13 part of chromosome 1. However, focal dystonia is rarely of genetic origin.
Secondary focal dystonia can occur as a result of trauma, exposure to certain medications, stroke, infection...
Symptoms of focal dystonia
The disease is usually caused by contractions that are difficult to control, not very painful and gradually progress to more painful spasms. Sometimes tremors can occur. The type of symptoms varies according to the location of the dystonia.
Diagnosing focal dystonia
Focal dystonia is diagnosed only clinically. No neurological examination can show the presence of the disease. The description of symptoms by the sick person is therefore very important. The diagnosis is in most cases made by a neurologist specialising in abnormal movements.
The electromyogram (EMG) is an examination that measures the activity of a muscle. The EMG is used to determine the muscle(s) involved in the spasms.
There are currently no treatments available to cure focal dystonia. Fatigue and stress tend to aggravate spasms. Rest and relaxation can reduce them.
There are treatments available to stabilize symptoms and freeze the progression of the disease.
It is the reference treatment for focal dystonia. It reduces spasms. The toxin is injected every 3 to 6 months or so, directly into the muscle affected by dystonia and partially paralyzes it.
Other symptomatic treatments
- Benzodiazepines that treat anxiety and spasms
- Muscle relaxants
- Anticholinergics block the action of acetylcholine, a neurotransmitter that contracts muscles
These drugs are used in combination with botulinum toxin injections to reduce involuntary contractions and associated pain.
In some cases where drug treatments and botulinum toxin injections have little or no effect, surgery may be considered. This consists in placing electrodes in the brain, connected to a box, sending small electrical waves in order to reduce or even eliminate the spasms.
It is important to include a physiotherapist to rebalance voluntary and involuntary muscle contraction. Physiotherapy sessions also allow the rehabilitation of movements blocked by spasms.
Focal dystonia in everyday life
Focal dystonia can be disabling on a daily basis. Socially, it may require the care of a psychologist. In some cases where the dystonia is physically disabling, home help can be provided. It can also lead to partial or total inability to work.
Sources : IFPEK, Orphanet, Amadys
Published 7 Jun 2018