Dystonia can have several origins:
- A genetic mutation
- A side effect of a drug such as antipsychotics or anti-nausea drugs. Another neurological disease or severe lack of oxygen in the brain.
The causes of dystonia
Generalized dystonias are generally genetic, hereditary, i.e. familial, or due to a new mutation appearing in the patient’s DNA (sporadic cases).
Primary generalized dystonia, also known as idiopathic torsional dystonia, begins in childhood and is due to a mutation in the DYT1 (Chromosome 9) gene encoding the TORSINE A protein. The function of this protein in the brain is not yet known for certain, but it may interact with dopamine, the neurotransmitter that enables communication between neurons.
The transmission of the DYT1 mutation is called autosomal dominant, meaning that a single allele of the mutated gene is sufficient to declare the disease.
There are also sporadic cases, i.e. patients with no family history but who carry the mutation.
Dopa-sensitive dystonia is also rare and inherited (dominant autosomal transmission). It is characterized by an improvement in symptoms when the patient is treated with a dopamine derivative.
Focal or segmental dystonia may have several non-genetic origins.
They may result, for example, from a severe lack of oxygen (hypoxia) in the brain at the time of birth or following a stroke, or from trauma or anatomical brain abnormalities. They can therefore appear at any age, depending on their cause.
Other neurological disorders such as multiple sclerosis or Wilson’s disease (copper build-up in cells) can also cause symptoms of involuntary muscular contractions of the dystonic type.
Finally, some anti-nausea or anti-psychotic treatments may cause dystonia.
Whether idiopathic, hereditary, or acquired, generalized or not dystonia results from dysfunctional neuron circuits and impaired communication between several brain regions involved in motor control: the basal ganglia, the cortex (the brain’s peripheral gray substance), and the cerebellum. Hyperactivity, i.e., excessive and uncontrolled communication of these structures, appears to be the cause of the observed dystonia symptoms in patients.
The basal ganglia are brain regions that initiate and harmonize voluntary muscle movements and suppress involuntary movements.
The cerebellum contributes to the coordination and synchronization of gestures and to the precision of movements.
At Paris Brain Institute
The research objectives of the ‘Mov'It: Mouvement, Investigations, Thérapeutique." Marie Vidailhet and Stéphane Lehéricy on dystonia are to restore cerebral function, enabling patients to regain optimal motor control. To achieve this, the team is developing multimodal research in imaging, neurophysiology and clinical research to understand the dysfunctions of the brain structures that cause dystonia and to develop solutions for repairing them. In particular, the team has demonstrated a strong involvement of the cerebellum, which has both a compensatory capacity and a capacity to alter movement.
A recent study by the MOV'IT team, led by Yulia Worbe (AP-HP/Sorbonne University), Emmanuel Roze (AP-HP/Sorbonne University), Pierre Pouget (CNRS) and Clément Tarrano (AP-HP/Sorbonne University), shows that the integration of visual signals is disrupted in patients with myoclonic dystonia.