ConditionBrain & nerves
Episodic Ataxia
Episodic ataxia (EA) is a group of rare inherited nerve conditions that cause sudden attacks of unsteadiness, poor coordination and slurred speech, lasting from seconds to hours, with normal or near-normal function between attacks. Attacks are often triggered by stress, exercise, sudden movement or caffeine. The two main types, EA1 and EA2, are caused by changes in genes for ion channels in the brain. Medicines such as acetazolamide can greatly reduce attacks, especially in EA2.
Also called: EA, paroxysmal ataxia, familial episodic ataxia, EA1, EA2
At a glance
- What it is
- Recurrent attacks of ataxia (loss of coordination and balance) with recovery between attacks.
- Main types
- EA1 (KCNA1 gene, brief attacks with muscle rippling) and EA2 (CACNA1A gene, longer attacks with vertigo and nystagmus).
- Inheritance
- Usually autosomal dominant, so a parent with it has a 50% chance of passing it on.
- Triggers
- Stress, exercise, sudden movements, startle, caffeine, alcohol and illness.
- Treatment
- Acetazolamide, 4-aminopyridine for EA2, anti-seizure drugs for EA1, and avoiding triggers.
When to get help
Call 911 or go to the ER
- A first-ever sudden loss of balance, slurred speech, double vision or weakness: call 911, because stroke must be ruled out
- An attack with a severe headache, confusion or loss of consciousness
See a doctor within a day or two
- Attacks becoming much more frequent, longer or different from usual
- Persistent unsteadiness between attacks that is getting worse
Book a routine appointment
- Recurrent brief episodes of clumsiness, staggering or slurred speech triggered by stress, exercise or startle
- Family members with similar episodes, migraines or seizures
- Side effects such as tingling, kidney stones or fatigue on acetazolamide
What happens in episodic ataxia
Ataxia means lack of coordination. In episodic ataxia, the cerebellum, the part of the brain that fine-tunes movement and balance, works abnormally during attacks. The cause is a gene change affecting ion channels, tiny pores that control how nerve cells fire. Faulty channels make nerve signaling unstable, especially under certain triggers.
At least eight types have been described, but EA1 and EA2 account for most cases.
Types of episodic ataxia
| EA1 | EA2 | |
|---|---|---|
| Gene | KCNA1 (potassium channel) | CACNA1A (calcium channel) |
| Typical onset | Childhood or teens | Childhood to early adulthood |
| Attack length | Seconds to minutes | Hours, sometimes days |
| Attack frequency | Can be many times a day | Days to weeks apart |
| Between attacks | Muscle rippling or twitching (myokymia) | Nystagmus (jerky eye movements), sometimes slowly progressive ataxia |
| Other features | Muscle stiffness, cramps, seizures in some | Vertigo, nausea, headache, migraine, weakness |
| Best-studied treatments | Carbamazepine, acetazolamide | Acetazolamide, 4-aminopyridine (dalfampridine) |
The same CACNA1A gene is involved in familial hemiplegic migraine type 1, a form of migraine, and spinocerebellar ataxia type 6 (see spinocerebellar ataxia), so different family members can have overlapping conditions.
Symptoms during an attack
- unsteadiness and staggering, sometimes falling
- clumsy hands and difficulty with fine tasks
- slurred speech (dysarthria)
- jerky eye movements (nystagmus), blurred or double vision
- vertigo and nausea (especially EA2)
- muscle stiffness or twitching (especially EA1)
- headache
- weakness in some people
Attacks usually end on their own, and the person returns to their baseline.
Triggers
- emotional stress and anxiety
- physical exercise or exertion
- sudden movements, standing up quickly, or being startled
- caffeine and alcohol
- fever and illness
- fatigue and hunger
- hormonal changes such as menstruation
Keeping a diary helps identify personal triggers.
Diagnosis
- History: the pattern of attacks, their length, triggers and family history are key. A video recorded during an attack is useful.
- Neurological examination: between attacks, it may show nystagmus (EA2) or muscle rippling (EA1).
- Electromyography (EMG): can detect myokymia in EA1.
- Brain MRI: usually normal, sometimes shows shrinkage of the cerebellum in EA2.
- Genetic testing: confirms KCNA1 or CACNA1A changes in many people, often using an ataxia gene panel.
- Excluding other causes: stroke or TIA, multiple sclerosis, vestibular migraine, seizures, inner ear disorders and metabolic conditions.
Treatment
There is no cure, but treatment can reduce attacks substantially.
- Acetazolamide: a carbonic anhydrase inhibitor that often dramatically reduces EA2 attacks and helps some people with EA1. Side effects include tingling in the fingers, altered taste of fizzy drinks, fatigue and kidney stones.
- 4-aminopyridine (dalfampridine): effective for EA2 in clinical studies.
- Anti-seizure medicines: carbamazepine, phenytoin or lamotrigine may help EA1.
- Trigger management: reducing caffeine and alcohol, regular sleep, stress management and warming up gradually before exercise.
- Physical therapy: balance and coordination training, especially if there is mild persistent ataxia.
- Genetic counseling for families.
Outlook
Episodic ataxia is lifelong, but it does not usually shorten life. Attacks may lessen with age in some people, especially with EA1. In EA2, some people develop slowly progressive balance problems between attacks over many years. With treatment and trigger avoidance, most people lead full lives, though safety precautions such as care with heights and driving during attack-prone periods may be needed.
Frequently asked questions
What is episodic ataxia?
Episodic ataxia is a rare inherited condition causing sudden attacks of unsteadiness, poor coordination and slurred speech that last seconds to hours, with normal function between attacks. It is caused by changes in genes that control ion channels in nerve cells.
What is the difference between EA1 and EA2?
EA1 causes very brief attacks lasting seconds to minutes, often with muscle rippling between attacks, and is caused by KCNA1 gene changes. EA2 causes longer attacks lasting hours, often with vertigo, nausea and eye movement abnormalities, and is caused by CACNA1A gene changes.
What triggers episodic ataxia attacks?
Common triggers include stress, exercise, sudden movements, being startled, caffeine, alcohol, fever and fatigue. Triggers vary between people, so keeping a symptom diary can help identify and avoid them.
How is episodic ataxia treated?
Acetazolamide is often very effective, particularly for EA2. 4-aminopyridine is another option for EA2, and anti-seizure medicines such as carbamazepine may help EA1. Avoiding triggers and physical therapy also help.
Is episodic ataxia inherited?
Most forms are inherited in an autosomal dominant pattern, meaning a person with the condition has a 50% chance of passing it to each child. Some cases arise from new gene changes. Genetic counseling can help families understand their risk.
Sources
This guide was written from current patient and clinical guidance, including:
- National Institute of Neurological Disorders and Stroke: Episodic ataxia
- MedlinePlus Genetics: Episodic ataxia
- GeneReviews (NCBI): Episodic ataxia type 2
- National Organization for Rare Disorders (NORD): Episodic ataxia
- Genetic and Rare Diseases Information Center (GARD): Episodic ataxia