Episodic ataxia (EA) is a neurological condition that impairs movement. It’s rare, affecting less than 0.001 percent of the population. People who have EA experience episodes of poor coordination and/or balance (ataxia) which can last from several seconds to several hours.
There are at least eight recognized types of EA. All are hereditary, though different types are associated with different genetic causes, ages of onset, and symptoms. Types 1 and 2 are the most common.
Read on to find more about EA types, symptoms, and treatment.
Symptoms of episodic ataxia type 1 (EA1) typically appear in early childhood. A child with EA1 will have brief bouts of ataxia that last between a few seconds and a few minutes. These episodes can occur up to 30 times per day. They may be triggered by environmental factors such as:
- emotional or physical stress
With EA1, myokymia (muscle twitch) tends to occur between or during ataxia episodes. People who have EA1 have also reported difficulty speaking, involuntary movements, and tremors or muscle weakness during episodes.
People with EA1 can also experience attacks of muscle stiffening and muscle cramps of the head, arms, or legs. Some people who have EA1 also have epilepsy.
EA1 is caused by a mutation in the KCNA1 gene, which carries the instructions to make a number of proteins required for a potassium channel in the brain. Potassium channels help nerve cells generate and send electrical signals. When a genetic mutation occurs, these signals may be disrupted, leading to ataxia and other symptoms.
This mutation is passed on from parent to child. It’s autosomal dominant, which means that if one parent has a KCNA1 mutation, each child has a 50 percent chance of getting it, too.
Episodic ataxia type 2 (EA2) usually appears in childhood or early adulthood. It’s characterized by episodes of ataxia that last hours. However, these episodes occur less frequently than with EA1, ranging from one or two per year to three to four per week. As with other types of EA, episodes can be triggered by external factors such as:
- physical exertion
People who have EA2 may experience additional episodic symptoms, such as:
- difficulty speaking
- double vision
- ringing in the ears
Other reported symptoms include muscle tremors and temporary paralysis. Repetitive eye movements (nystagmus) may occur between episodes. Among people with EA2, approximately
Similar to EA1, EA2 is caused by an autosomal dominant genetic mutation that’s passed on from parent to child. In this case, the affected gene is CACNA1A, which controls a calcium channel.
This same mutation is associated with other conditions, including familiar hemiplegic migraine type 1 (FHM1), progressive ataxia, and spinocerebellar ataxia type 6 (SCA6).
Other types of EA are extremely rare. As far as we know, only types 1 and 2 have been identified in more than one family line. As a result, little is known about the others. The following information is based on reports within single families.
- Episodic ataxia type 3 (EA3). EA3 is associated with vertigo, tinnitus, and migraine headaches. Episodes tend to last a few minutes.
- Episodic ataxia type 4 (EA4). This type was identified in two family members from North Carolina, and is associated with late-onset vertigo. EA4 attacks typically last several hours.
- Episodic ataxia type 5 (EA5). Symptoms of EA5 appear similar to those of EA2. However, it’s not caused by the same genetic mutation.
- Episodic ataxia type 6 (EA6). EA6 has been diagnosed in a single child who also experienced seizures and temporary paralysis on one side.
- Episodic ataxia type 7 (EA7). EA7 has been reported in seven members of a single family over four generations. As with EA2, onset was during childhood or young adulthood and attacks last hours.
- Episodic ataxia type 8 (EA8). EA8 has been identified among 13 members of an Irish family over three generations. Ataxia first appeared when the individuals were learning to walk. Other symptoms included unsteadiness while walking, slurred speech, and weakness.
Symptoms of EA occur in episodes that can last several seconds, minutes, or hours. They may occur as little as once per year, or as often as several times per day.
In all types of EA, episodes are characterized by impaired balance and coordination (ataxia). Otherwise, EA is associated with a wide range of symptoms which appear to vary a lot from one family to the next. Symptoms can also vary between members of the same family.
Other possible symptoms include:
- blurred or double vision
- involuntary movements
- migraine headaches
- muscle twitching (myokymia)
- muscle spasms (myotonia)
- muscle cramps
- muscle weakness
- nausea and vomiting
- repetitive eye movements (nystagmus)
- ringing in the ears (tinnitus)
- slurred speech (dysarthria)
- temporary paralysis on one side (hemiplegia)
Sometimes, EA episodes are triggered by external factors. Some known EA triggers include:
- hormonal changes
- illness, especially with fever
- physical activity
More research needs to be done to understand how these triggers activate EA.
Episodic ataxia is diagnosed using tests such as a neurological examination, electromyography (EMG), and genetic testing.
After diagnosis, EA is typically treated with anticonvulsant/antiseizure medication. Acetazolamide is one of the most common drugs in the treatment of EA1 and EA2, though it’s more effective in treating EA2.
Alternative medications used to treat EA1 include carbamazepine and valproic acid. In EA2, other drugs include flunarizine and dalfampridine (4-aminopyridine).
Your doctor or neurologist might prescribe additional drugs to treat other symptoms associated with EA. For instance, amifampridine (3,4-diaminopyridine) has proved useful in treating nystagmus.
In some cases, physical therapy may be used alongside medication to improve strength and mobility. People who have ataxia might also consider diet and lifestyle changes to avoid triggers and maintain overall health.
Additional clinical trials are required to improve treatment options for people with EA.
There’s no cure for any type of episodic ataxia. Though EA is a chronic condition, it doesn’t affect life expectancy. With time, symptoms sometimes go away on their own. When symptoms persist, treatment can often help ease or even eliminate them altogether.
Talk to your doctor about your symptoms. They can prescribe helpful treatments that help you maintain a good quality of life.