Episodic Ataxia and the Inability to Control Movement

Episodic ataxia is a group of uncommon disorders that cause periods during which a person is unable to control bodily movements (ataxia). Episodes can last anywhere from seconds to days and can occur several times a day or once or twice every few months.

In some people, ataxia gets progressively worse. In others, it may disappear over time. The life expectancy of someone with episodic ataxia is not any shorter.

This article explains the different types and causes of episodic ataxia. It also covers how episodic ataxia is diagnosed and treated.

Types of Episodic Ataxia

Episodic ataxia is uncommon and affects fewer than one in 100,000 people. There are at least 11 types of episodic ataxia. Type 2 is the most common.

Episodes of poor coordination and balance characterize all types of episodic ataxia. The exact symptoms, duration, severity, and triggers of the ataxic episodes vary from type to type.

Episodic Ataxia Type 1

The spells of unsteadiness caused by episodic ataxia type 1 (EA1) usually last only for minutes at a time. These periods are often brought on by exercise, ​caffeine, or stress. Sometimes there may be a rippling of the muscles (myokymia) that comes on with the ataxia. Symptoms usually begin in adolescence.

The easiest way to test for EA1 is to get genetic testing. An MRI may be done to rule out other potential causes of ataxia, but in the case of EA1, an MRI will only show mild shrinkage of the middle of the cerebellum which is called the vermis.

Episodic Ataxia Type 2

Episodic ataxia type 2 (EA2) is associated with attacks of severe vertigo (dizziness) and sometimes nausea and vomiting that last from hours to days. Nystagmus, a condition in which the eyes move repetitively and uncontrollably, can be present not only during but also between attacks.

Unlike EA1, episodic ataxia type 2 can lead to injury to the cerebellum, the part of the brain responsible for coordination. Due to this slowly worsening damage, people with EA2 can lose voluntary control of the muscles in between their periodic attacks as well. Like EA1, people with EA2 usually first feel symptoms in adolescence.

Other Episodic Ataxias

The remaining episodic ataxia are very rare. Many of the less common episodic ataxia are very similar in appearance to EA1 and EA2 but have different genetic mutations as the cause. Each of these subtypes has been reported in only one or two families.

• EA3 have brief attacks involving a lack of muscle coordination and control, with dizziness and muscle rippling.
• EA4 is more like EA2, with unusual eye movements like nystagmus that persists even when there is no active attack, though attacks are relatively brief. EA4 is unique in that it doesn’t respond well to the treatments used for other episodic ataxia.
• EA5 has attacks that go on for hours like EA2. It has been reported in a French Canadian family.
• EA6 is caused by a mutation that can also be associated with seizures, migraine, and hemiplegia, again like EA2.
• EA7 was identified in just one family and is very much like EA2 except that the neurological exam is normal in between attacks.
• EA8 shows its symptoms in early infancy with attacks lasting from minutes to a full day. It has been found within one family and responds to clonazepam.

Not all types of episodic ataxia are numbered, such as episodic ataxia with paroxysmal choreoathetosis and spasticity. Paroxysmal choreoathetosis refers to uncontrollable movements of the arm, leg, face, and body muscles. There is also episodic ataxia of late onset which typically occurs after 60 years of age in people with no family history. This form progresses slowly and does not respond well to treatment.

Causes of Episodic Ataxia

Episodic ataxia is a genetic disorder that is inherited from a biological parent. It is autosomal dominant, meaning only one parent needs to have the abnormal gene for it to be passed down to the child. However, sometimes the mutation can occur on its own.

Episodic ataxia type 1 is caused by a mutation in a potassium ion channel. This channel usually permits electrical signaling in nerve cells, and these signals may become abnormal when the channel is changed by a genetic mutation.

Episodic ataxia type 2 is caused by a mutation in a calcium channel. This same calcium channel is also mutated in other diseases such as spinocerebellar ataxia type 6 and familial hemiplegic migraine. Some people with EA2 also have symptoms that are reminiscent of those other diseases.

Diagnosis of Episodic Ataxia

Before reaching a diagnosis of a relatively rare disorder like episodic ataxia, healthcare providers will want to rule out other more common causes of ataxia. However, if there is a clear family history of ataxia, it may be worth obtaining genetic testing.

Most physicians recommend working with a genetic counselor when seeking this kind of testing. While the results of a genetic test may seem straightforward, there are often important nuances that might otherwise be overlooked. It is important to know what a genetic test means not only for you but your family as well.

Treatment for Episodic Ataxia

Symptoms of both EA1 and EA2 improve with acetazolamide, a medication that is usually used as a diuretic or to help change acidity levels in the blood. Dalfampridine has also been shown to be effective in episodic ataxia type 2 as well. Physical therapy may be helpful to manage the ataxia when it is present.

While episodic ataxia is not common, a diagnosis has implications for both the patient and their family. It is important for neurologists and patients to think about episodic ataxia when there is a family history of clumsiness.

Summary

Episodic ataxia refers to a group of uncommon neurological conditions affecting coordination and balance. The types of episodic ataxia are distinguished by their symptoms and other factors. Episodes of uncontrollable muscle movements vary in length and frequency and may improve over time.

Genetic testing is used to diagnose episodic ataxia. Genetic counseling is available to help families with rare genetic disorders like episodic ataxia. Treatment for episodic ataxia may involve medication and physical therapy.

Talk to a healthcare provider if you are experiencing uncontrollable muscle movements. Your provider will want to rule out more common causes and make sure you're getting appropriate treatment.