Episodic Ataxia
Episodic ataxia is a rare, inherited neurological disorder that causes brief episodes of poor coordination, dizziness, and other neurological symptoms, often triggered by stress or certain substances.
Overview
Episodic ataxia is a group of related conditions that affect the nervous system and cause problems with movement and coordination. People with episodic ataxia have episodes of ataxia—poor coordination and balance. During these episodes, many also experience vertigo, nausea, vomiting, migraines, blurred or double vision, slurred speech, and ringing in the ears (tinnitus). Seizures, muscle weakness, and one‑sided paralysis (hemiplegia) may also occur. Between episodes, affected individuals may have no signs or symptoms, although some continue to experience ataxia that can worsen over time.
Episodes can begin at any age from early childhood to adulthood and last from seconds to days. The frequency ranges from several episodes per day to one or two every few months.
Some children with episodic ataxia have delayed development of speech or motor skills and may have learning difficulties.
Researchers have identified at least 11 types of episodic ataxia, distinguished by their pattern of signs and symptoms, age of onset, length of episodes, and genetic cause.
Symptoms
- Ataxia (poor coordination and balance)
- Vertigo
- Nausea and vomiting
- Migraines
- Blurred or double vision
- Slurred speech
- Tinnitus (ringing in the ears)
- Seizures
- Muscle weakness
- Hemiplegia (one‑sided paralysis)
- Myokymia (fine muscle twitching or rippling)
- Nystagmus (rapid, involuntary eye movements)
Causes & Risk Factors
Episodic ataxia is caused by variants (mutations) in genes that encode proteins involved in ion transport in the nervous system. The most well‑studied genes are:
- KCNA1 – encodes a potassium‑ion channel; mutations cause type 1
- CACNA1A – encodes a calcium‑ion channel; mutations cause type 2
- SLC1A3 – encodes a chloride‑ion transporter that also moves glutamate; mutations cause type 6
Variants in these genes alter ion transport, potentially over‑exciting neurons and disrupting normal communication. The genetic causes of other types of episodic ataxia have not yet been identified or are poorly documented.
Other genes implicated in related disorders include SCN2A and FGF14.
Inheritance
This condition follows an autosomal dominant pattern: one copy of the altered gene in each cell is sufficient to cause the disorder. In some cases, an affected person inherits the variant from an affected parent; other cases arise from a new mutation (de novo) and occur in people with no family history.
Frequency
Episodic ataxia is uncommon, affecting less than 1 in 100,000 people. Only types 1, 2, and 6 have been identified in more than one family, with type 2 being the most common form.
Diagnosis
Diagnosis is based on clinical presentation and confirmed by genetic testing. The following registries provide information on available tests:
- Genetic Testing Registry: Episodic ataxia type 1
- Genetic Testing Registry: Episodic ataxia type 2
- Genetic Testing Registry: Episodic ataxia type 7
Management & Prevention
Episodes can be triggered by environmental factors such as stress, caffeine, alcohol, certain medications, physical activity, and illness. Managing these triggers may help reduce episode frequency and severity. No specific pharmacologic treatment is described in the source material.
Other Names
- EA (Episodic Ataxia)
Resources
Patient Support and Advocacy
- National Organization for Rare Disorders (NORD)
Clinical Trials
- ClinicalTrials.gov
Gene and Disease Catalogs
- CALCIUM CHANNEL, VOLTAGE‑DEPENDENT, BETA‑4 SUBUNIT; CACNB4
- EPISODIC ATAXIA, TYPE 1; EA1
- EPISODIC ATAXIA, TYPE 2; EA2
- EPISODIC ATAXIA, TYPE 3; EA3
- EPISODIC ATAXIA, TYPE 4; EA4
- EPISODIC ATAXIA, TYPE 7; EA7
- SOLUTE CARRIER FAMILY 1 (GLIAL HIGH AFFINITY GLUTAMATE TRANSPORTER), MEMBER 3; SLC1A3
Scientific Literature
- PubMed
Medical Encyclopedias
- Genetics
- Movement – uncoordinated
- Vertigo‑associated disorders
Understanding Genetics
- What is the prognosis of a genetic condition?
- How can gene variants affect health and development?
- What does it mean if a disorder seems to run in my family?
- What are the different ways a genetic condition can be inherited?
- How are genetic conditions treated or managed?