Dystonia is a movement disorder in which muscles contract involuntarily, causing repetitive or twisting movements of a limb or body part.
It is distinguished between primary (or primitive) dystonia and secondary dystonia.
Primary dystonia
It is most often sporadic and localized. The different forms of primary dystonia are:
- Generalized dystonia. It is a dystonia which is localized at the beginning then which generalizes all the more so as it begins early, with for consequence a severe incapacity. It is an autosomal dominant disease (also called Schwalbe-Ziehen-Oppenheim disease).
- focal dystonia. It is more common in women, except for writer’s cramp.
- Spasmodic torticollis. It affects the muscles of the neck, causing lateral deviation of the head (torticollis), and sometimes extension (retrocollis) or flexion (antecolis) of the head. About 3 per 10,000 people suffer from it.
- Blepharospasm. It is characterized by sustained contraction of the orbicularis of the eyelids, often triggered by bright light or emotional stress.
- Oromandibular facial dystonia. It concerns the muscles of the face, lips, tongue and masticatory muscles, innervated by the facial nerve.
- Writer’s cramp. It is one of the frequent forms in adults, which is characterized by a contraction of the muscles of the fingers. This condition is especially present in high-risk professions that overuse writing (teachers, doctors, accountants) or in individuals who have poor gestural habits. Spasms begin in the fingers, then spread to the hand and upper limb.
- Spasmodic dysphonia. It is caused by a spasmodic contraction of the adductors of the vocal cords.
Secondary dystonia
The main cause of secondary dystonia is the inadequate intake of a drug (iatrogenic dystonia) or the presence of a cerebrovascular accident (CVA) of ischemic or hemorrhagic origin. Appearing from a few weeks to a few years after a stroke, secondary dystonia rather concerns the discal part of the contralateral limbs (hemidystonia). The cause can be detected by magnetic resonance imaging. Wilson’s disease is a hereditary neurological disease caused by an accumulation in the body of copper which cannot be eliminated, and which results, among other things, in dystonia.
Causes
The exact cause of dystonia is not known. It may be due to a problem with nerve transmission in several regions of the brain. Some forms of dystonia are hereditary.
Dystonia can also be a symptom of another disease or condition, including:
- Parkinson’s disease
- Huntington’s disease
- Wilson’s disease
- A traumatic brain injury
- A birth injury
- A cerebral vascular accident
- A brain tumor or certain disorders that develop in some people with cancer (paraneoplastic syndromes)
- Oxygen deprivation or carbon monoxide poisoning
- Infections, such as tuberculosis or encephalitis
- Reactions to certain medications or heavy metal poisoning
Complications
Depending on the type of dystonia, complications can include:
- Physical disabilities that affect your performance of daily activities or specific tasks
- Difficulty seeing that affects your eyelids
- Difficulty moving the jaw, swallowing, or speaking
- Pain and fatigue, due to constant contraction of your muscles
- A mental health disorder (depression, anxiety)
Diagnostic
The doctor will begin by reviewing the medical history, performing a physical examination, and determining the causes through the following tests:
- Blood or urine tests. These tests can reveal signs of toxic products.
- MRI or CT scan. These imaging tests can identify abnormalities in the brain, such as tumors, lesions, or signs of stroke.
- Electromyography (EMG). This test measures the electrical activity in the muscles.
- Genetic test. Some forms of dystonia are associated with certain gene mutations.
Treatment
Medications
Injections of botulinum toxin into specific muscles can reduce or eliminate muscle twitching and improve posture. The injections are usually repeated every three to four months.
Side effects are usually mild and temporary. They may include weakness, dry mouth, or voice changes.
Other drugs target neurotransmitters in the brain that affect muscle movement, including:
- Carbidopa-levodopa . This medication increases levels of the neurotransmitter dopamine.
- Trihexyphenidyl and benztropine. Both of these drugs act on neurotransmitters besides dopamine.
- Diazepam, clonazepam, and baclofen.
Therapy
Your doctor might suggest:
- Physiotherapy or occupational therapy to help relieve symptoms.
- Speech therapy if dystonia affects the voice
- Stretching or massage to relieve muscle pain
Surgery
If the symptoms are severe, the doctor might recommend:
- Deep brain stimulation.
- Selective denervation surgery. This procedure involves cutting the nerves that control muscle spasms.