Dystonia can be classed as primary or secondary depending on whether it has been passed down through the family or is due to an underlying cause.
Primary dystonia
Most cases of primary dystonia are thought to be caused by problems with a part of the brain called the basal ganglia.
The basal ganglia is a collection of brain cells at the front of the brain responsible for sending messages from the brain to various muscles to move them. This is done by using special, messenger-chemicals called neurotransmitters.
In cases of primary dystonia, it is thought that the basal ganglia doesn’t produce enough neurotransmitters, or it produces the wrong type of neurotransmitters, resulting in problems with muscle function.
In cases of early-onset dystonia, it appears that the basal ganglia doesn’t develop in the right way due to mutated (altered) genes that you inherit from your parents.
There are 12 types (or sub-types) of dystonia that are currently linked to genetic mutations, including generalised dystonia, dopa-responsive dystonia and paroxysmal dystonia.
Read more about the different types of dystonia.
The genes responsible for these types of dystonia are passed down through families in a pattern that’s known as autosomal dominant. This means that if you have one of these abnormal genes, there’s a 1 in 2 chance that your children will inherit that gene and develop dystonia.
Late-onset primary dystonia is poorly understood and its cause (or causes) are unknown.
Secondary dystonia
Secondary dystonia, also known as acquired dystonia, can have a wide range of causes, including:
- Parkinson’s disease – a neurological condition caused by a lack of a neurotransmitter called dopamine
- Huntington’s disease – a genetic (inherited) condition caused by a lack of cholesterol in the brain
- Wilson’s disease – a genetic condition that leads to a build-up of copper in the body’s tissues
- multiple sclerosis – a condition caused by damage to the nervous system
- cerebral palsy – a condition caused by brain damage that occurs before or quickly after birth
- certain medications, such as the one used to treat epilepsy, can cause dystonia as a side effect in a small number of people
- infections, such as HIV or encephalitis (a brain infection)
- injury – to the skull or spine
- brain tumours
- stroke
- poisoning, such as carbon monoxide poisoning
