Neuromyelitis optica spectrum disorder (NMO) is a chronic (long-term) condition. It causes episodes of swelling (inflammation) of the brain, spinal cord, and eye nerves. These periods of inflammation – or attacks – last for a short time, though symptoms from these attacks often persist. There may be weeks to years between attacks.1
The inflammation from NMO can damage nerves and make walking or moving difficult. This can have a large impact on your quality of life and daily activities. You may experience:1,2
- Muscle weakness
- Vision problems
- Limb pain
- Paralysis
NMO can also cause a symptom called paroxysmal dystonia. Paroxysmal dystonia affects the muscles and can also cause mobility issues.1,2
What is paroxysmal dystonia?
Paroxysmal dystonia is a neurological (nerve-based) movement disorder. It causes uncontrolled muscle spasms during episodes. The muscles contract (tighten) and cause repetitive movements, most commonly in the limbs. These movements can be painful. Episodes typically last a few seconds to several minutes and can occur multiple times a day.2
Paroxysmal dystonia in NMO might cause:2,3
- Uncontrolled twisting of limbs or face muscles
- Tremor or shaking
- Pain
Research on paroxysmal dystonia and NMO is limited. But 1 study found that paroxysmal dystonia is the most common movement disorder caused by NMO.3-5
Experts think that about 15 to 40 percent of people with NMO experience paroxysmal dystonia. But it is possible that these numbers are lower than they should be. That is because people may not know to name what is happening as paroxysmal dystonia.3-5
Why do people with NMO get paroxysmal dystonia?
Paroxysmal dystonia happens when the signal from the brain or the spinal cord is incorrect. Through cells in the spinal cord, our brain sends signals to muscles in our body and limbs. Problems with this signal can sometimes cause uncontrolled movement, like in paroxysmal dystonia.2-4
We do not understand exactly how NMO causes paroxysmal dystonia. But NMO also affects the brain and spinal cord.3-5
Nerve fibers in our bodies have a protective cover called myelin. Damage to this coating is called demyelination. NMO damages myelin, which affects nerve signals. NMO also damages nerves directly. Both of these processes can contribute to conditions like paroxysmal dystonia.3-5
How is paroxysmal dystonia diagnosed?
A doctor will usually start with your medical history when diagnosing paroxysmal dystonia. If possible, try to record video of the abnormal movements. Then you can show what is happening to your doctor.2
Your doctor may also use tests to help diagnose paroxysmal dystonia or other causes of abnormal movements. The tests might include:2
- Electroencephalogram (EEG) – a test to measure brain waves
- Brain imaging – scans like magnetic resonance imaging (MRI) or computed tomography (CT)
- Blood tests
How is paroxysmal dystonia treated?
Paroxysmal dystonia can be difficult to treat. You may have to try several drugs before you find one that works. Paroxysmal dystonia should be treated by a neurologist (a doctor who specializes in nerve problems).2
Paroxysmal dystonia is often treated with classes of drugs classically used as anticonvulsants. These drugs work by changing nerve activity in the brain and spinal cord. Medicines your doctor might try for paroxysmal dystonia include:1-3
- Phenytoin
- Valproate
- Carbamazepine
- Diazepam
Your doctor may also suggest other drugs to treat paroxysmal dystonia. These include:1-3,6
- Anticholinergics – a type of drug that targets specific neurotransmitters (chemicals that send nerve signals)
- Levodopa – a drug often used to treat Parkinson’s disease
- Clonazepam or haloperidol – drugs that are often used to treat mood disorders