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Dystonie

Dystonia

Causes, biological mechanisms, symptoms, diagnosis and treatment.

Last update: 21/02/2025 Reading time: 1min

Dystonia is a rare disease affecting around 20,000 people in France, most of whom are women. Onset can occur at any age and typically presents as long-lasting muscle contractions, resulting in abnormal postures and positions. There is a difference between primary dystonia, caused by genetic mutations, and secondary dystonia, which can be caused by another neurological condition or a drug. When only one part of the body is affected, the condition is known as focal dystonia. If two adjacent parts of the body are affected by the muscle contractions, the dystonia is referred to as segmental dystonia. Some patients can also have generalised dystonia if the torso and two other parts of the body are affected.

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Causes and biological mechanisms

Biological mechanisms and causes of dystonia

Primary, or idiopathic, dystonia is caused by a genetic mutation, either inherited from a family member or a sporadic mutation, and usually begins in childhood. Secondary dystonia is caused by brain damage caused by a severe deprivation of oxygen to the brain at birth or later on, by another neurological condition such as multiple sclerosis, a stroke or alternatively by a side effect of drugs such as antipsychotics or antiemetics (anti-nausea drugs).

Dystonia is caused by hyperactivity in certain areas of the brain. These include the brain’s deep structures, the central basal nuclei or basal ganglia, which control part of motor function, the cortex and the cerebellum.

Symptoms and diagnosis

Dystonia symptoms and diagnosis 

Dystonia presents as involuntary and long-lasting contractions of the muscles of a part of the body, causing long-term changes to the position of the affected limb and the trunk.

All muscles of the body can be affected. A distinction is made between generalised dystonia, which is very rare, and focal dystonia, which is more common:

  • Dystonia of the neck: spasmodic torticollis, usually laterocollis (sideways), but sometimes antecollis (forwards) or retrocollis (backwards).
  • Dystonia of the hand: writers’ cramp, which appears during writing.
  • Dystonia of the larynx: spasmodic dysphonia or tightening of the vocal cords.
  • Blepharospasm, repeated, involuntary contractions of the eyelids.
  • Dystonia of the foot.

It can be difficult to diagnose dystonia. Diagnosis is mainly made through a clinical examination of a patient’s symptoms. MRI brain imaging can help with diagnosis. The clinician looks at whether triggering factors such as another neurological disease or hypoxia are the cause of the dystonia. An investigation into family medical history is also conducted if the onset of the disease does not have a primary cause. If there is family history or there is no identified cause, the patient may be referred for DNA sequencing to look for the genetic mutation that caused the disease.

Treatments

Treatments for dystonia

The different types of dystonia – focal, segmental or generalised – are treated differently. 

In generalised dystonia cases, treatment is based on muscle relaxants or anticholinergics. Severe forms can also be treated through non-invasive transcranial magnetic stimulation, or deep brain stimulation. In some very severe cases, ablative surgery of an area of the brain may be considered. Treatments for focal or segmental dystonia involve treatment using injections of botulinum toxin.