Generalised dystonia is generally genetic, hereditary, i.e. familial, or due to a new mutation in the patient’s DNA (sporadic cases).
Primary generalised dystonia, also known as idiopathic torsional dystonia, begins in childhood and is due to a mutation in the DYT1 gene (chromosome 9) coding for the protein TORSINE A. 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.
Transmission of the DYT1 gene mutation is autosomal dominant, meaning that a single allele of the mutated gene is sufficient to cause 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 hereditary (autosomal dominant transmission). It is characterised by an improvement in symptoms when the patient is treated with a dopamine derivative.
Focal or segmental dystonias can 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 trauma, or from anatomical cerebral anomalies. They can therefore appear at any age, depending on their cause.
Other neurological disorders such as multiple sclerosis or Wilson’s disease (accumulation of copper in the cells) can also cause symptoms of involuntary muscular contractions of the dystonic type.
Lastly, certain anti-nausea or anti-psychotic treatments can be the cause of the appearance of dystonia.
Whether idiopathic, hereditary or acquired, generalised or not, dystonia results from a dysfunction of neuronal circuits
and impaired communication between several brain regions involved in motor control: the basal ganglia, the cortex (the brain’s peripheral grey matter) and the cerebellum. Hyperactivity, i.e. excessive and uncontrolled communication between these structures, appears to be the cause of the dystonia symptoms observed in patients.
The basal ganglia are brain regions that initiate and harmonise voluntary muscle movements and suppress involuntary movements.
The cerebellum contributes to the coordination and synchronisation of gestures, and to the precision of movements.
Dystonia research at the Paris Brain Institute
The research objectives of the “Mov’It: Movement, Investigatios, Therapeutics“. 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.