Episodic ataxia
Episodic ataxia
Episodic ataxia (EA) is a hereditary nervous-system disorder that causes sudden bouts of poor coordination (ataxia) that come and go. Some people also have ongoing tremors (myokymia). Attacks can be triggered by stress, being startled, or exertion, and they may start in childhood. Some patients have migraine or progressive cerebellar problems. Acetazolamide helps in some cases, but not everyone responds.
Types and genes
- EA1 (KCNA1): Attacks of ataxia with myokymia, usually starting in childhood or adolescence and lasting seconds to minutes. The KCNA1 gene makes a potassium channel important for inhibiting certain cerebellar neurons. Many mutations reduce current or disrupt channel function, altering cerebellar output.
- EA2 (CACNA1A): Attacks of ataxia lasting hours to days, often with migraine, nystagmus, vertigo, or difficulty speaking. Triggers include exercise, heat, caffeine, or alcohol. Onset in childhood. Mutations reduce CaV2.1 calcium currents in Purkinje cells, affecting cerebellar signaling.
- EA3: Similar to EA1 but with tinnitus and vertigo. Attacks are usually brief (less than 30 minutes) and may occur once or twice daily. Onset in childhood. Gene not yet known; acetazolamide helps some people.
- EA4: Extremely rare. Onset later in life with vertigo and ataxia and eye-movement problems (smooth pursuit and nystagmus). Described in a few North Carolina families; exact gene location unknown.
- EA5 (CACNB4): Overlaps with juvenile myoclonic epilepsy; attacks include ataxia and seizures and may include nystagmus between attacks. Often responsive to acetazolamide. CACNB4 encodes a subunit that affects calcium-channel activity; a mutation increases current and can cause hyperexcitability.
- EA6 (SLC1A3): Very rare. A mutation in the EAAT1 glutamate transporter reduces glutamate uptake, likely causing increased brain excitability. Attacks include ataxia and seizures and may be linked to migraines; fever can trigger episodes. Affects cerebellum and brainstem.
Treatment and outlook
- Acetazolamide helps some people with EA, but not everyone.
- Long-standing attacks can lead to tendon or muscle problems that may require surgery in rare cases.
EA is a spectrum of related conditions, all involving episodes of impaired movement due to specific ion-channel or transporter gene mutations affecting brain signaling.
This page was last edited on 3 February 2026, at 00:06 (CET).