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Health condition

Episodic ataxia type 2, a CACNA1A channelopathy that responds to acetazolamide.

Recurrent attacks of ataxia, dysarthria, vertigo and nystagmus - triggered by stress, exercise, alcohol and heat. Rare, inherited and treatable.

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A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against Ataxia UK, specialist ataxia services and peer-reviewed neurogenetics sources.

  • 03

    Current for 2026

    Reflects modern UK practice including CACNA1A genetic testing and acetazolamide-first management.

Key facts

EA2 at a glance.

The essentials, in plain English - what it is, how it presents and how UK specialist ataxia services treat it.

  • What it is

    A rare autosomal dominant channelopathy of the P/Q-type voltage-gated calcium channel - causing episodes of ataxia lasting hours to days.

  • The gene

    CACNA1A mutations - allelic with familial hemiplegic migraine and spinocerebellar ataxia type 6 (SCA6).

  • Onset

    Usually childhood or adolescence - often with a positive family history down the generations.

  • Hallmark

    Recurrent ataxia, dysarthria, vertigo and nystagmus - triggered by stress, exercise, alcohol, coffee, heat and missed meals.

  • Interictal signs

    Downbeat and gaze-evoked nystagmus between attacks, and in some, slowly progressive cerebellar ataxia.

  • First-line therapy

    Acetazolamide is highly effective at reducing episode frequency and duration - specialist prescribed and monitored.

Why this guide matters

A rare condition with a clear treatment plan.

EA2 is often mistaken for migraine, vestibular disease or functional neurology for years. The three points below shape the rest of this page.

  • Family history is a big clue

    Autosomal dominant inheritance means episodes, migraine or cerebellar signs often run down one side of the family - always worth asking.

  • Acetazolamide changes daily life

    A well-tolerated dose cuts episode frequency for most people, often dramatically - it is a diagnostic and therapeutic mainstay.

  • Specialist services matter

    CACNA1A genetics, cascade testing and MDT ataxia care sit in commissioned centres - Sheffield, Queen Square, Cambridge and Great Ormond Street.

How the diagnosis is made

From first episode to a genetic answer.

The steps a UK neurology or neurogenetics service will normally follow, in order - so you know what to expect and why each test is done.

  1. 01

    Assessing

    Detailed episode history

    Duration, triggers, symptoms during and between attacks - the pattern is often diagnostic before any test.

  2. 02

    Assessing

    Family history

    Autosomal dominant inheritance means episodes, migraine or cerebellar signs often run down one side of the family.

  3. 03

    Assessing

    Neurological examination

    Looking for interictal downbeat and gaze-evoked nystagmus, mild cerebellar signs and any progressive features.

  4. 04

    Confirming

    MRI brain

    Usually normal, or shows mild cerebellar vermis atrophy - helps exclude MS, tumour and structural mimics.

  5. 05

    Confirming

    Vestibular and EEG testing

    Ictal and interictal EEG plus ambulatory vestibular tests - to separate EA2 from migraine, vestibular and epileptic mimics.

  6. 06

    Genetics

    CACNA1A genetic testing

    Neurogenetics-led testing through a specialist commissioned centre - Queen Square, Cambridge or a regional service.

  7. 07

    Genetics

    Specialist ataxia MDT

    Referral to a specialist commissioned ataxia service - Sheffield National Ataxia Centre, Queen Square or Great Ormond Street for children.

Typical timeline: from first specialist visit to a genetic answer within a few months.

Symptoms

What an EA2 episode looks like.

The core pattern - ataxia, dysarthria, vertigo and nystagmus - plus interictal signs and the migraine and hemiplegic overlaps to watch for.

  • Recurrent episodic ataxia

    Sudden unsteady gait, limb ataxia and imbalance - typically lasting six to twelve hours, sometimes days.

  • Dysarthria during attacks

    Slurred, scanning speech that comes on with the ataxia and settles as the episode passes.

  • Vertigo and nausea

    True rotational vertigo, often with nausea and vomiting - easily mistaken for a vestibular attack.

  • Nystagmus

    Downbeat and gaze-evoked nystagmus - present between attacks in many, and a real diagnostic clue.

  • Trigger-driven episodes

    Stress, exercise, alcohol, caffeine, heat, illness, emotion and missed meals commonly set attacks off.

  • Migraine overlap

    Around half of people with EA2 also have migraine - and some have hemiplegic migraine in the family.

  • Progressive cerebellar signs

    In some, a slowly progressive cerebellar ataxia develops between attacks over years.

  • Red flag - focal weakness or coma

    Hemiplegic features, seizures or reduced consciousness need urgent assessment - overlap with familial hemiplegic migraine.

Treatment

How EA2 is treated in the UK.

Acetazolamide first, then 4-aminopyridine, trigger management, vestibular rehab, migraine co-management and an MDT specialist service.

  • Acetazolamide (Diamox)

    First-line - a carbonic anhydrase inhibitor at 250 to 500 mg twice daily. Highly effective at cutting episode frequency and duration.

  • 4-aminopyridine (4-AP)

    A potassium channel blocker used as an alternative or adjunct in specialist ataxia clinics - dalfampridine is an emerging option.

  • Trigger avoidance

    Identifying and reducing stress, alcohol, caffeine, heat and missed meals often cuts attacks as much as medication.

  • Vestibular rehabilitation

    Targeted physiotherapy and vestibular work help balance, gaze stability and confidence between attacks.

  • Migraine co-management

    Where migraine coexists - and it often does - separate migraine prevention improves overall symptom load.

  • Nutritional and lifestyle plan

    Regular meals, hydration and paced exercise reduce trigger exposure day to day.

  • Genetic counselling

    CACNA1A cascade testing, reproductive options and, where wanted, pre-implantation genetic diagnosis via a specialist service.

  • MDT specialist ataxia care

    Neurology, neurogenetics, psychology, physiotherapy and occupational therapy through a commissioned ataxia service - plus Ataxia UK for peer support.

What this guide is based on

The sources behind every claim on this page.

UK specialist ataxia guidance, commissioned service standards and peer-reviewed neurogenetics literature current at the time of review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your neurologist or neurogenetics team knows your history and family in detail and can tell you which parts apply to you. If in doubt, get seen.

  • Ataxia UK. Guidance for the diagnosis and management of the hereditary ataxias.

  • NHS England. Specialised commissioned service specifications for complex ataxia.

  • Association of British Neurologists. Consensus on episodic ataxias and channelopathies.

  • Peer-reviewed neurogenetics literature on CACNA1A phenotypes - EA2, familial hemiplegic migraine and SCA6.

Red flags

When EA2 needs urgent attention.

Most attacks are self-limiting and treated with acetazolamide. These are the situations that need something more - and where a specialist opinion is essential.

  • Sudden focal weakness

    Hemiplegic features or facial droop - consider familial hemiplegic migraine or stroke and seek urgent neurology assessment.

  • Reduced consciousness during an attack

    Prolonged coma-like states can occur with severe CACNA1A phenotypes - needs emergency assessment.

  • New seizures

    Epilepsy occurs in some CACNA1A families - any new seizure activity warrants review and EEG.

  • Progressive cerebellar decline

    Worsening interictal ataxia between attacks suggests progressive cerebellar disease and needs specialist review.

  • Pregnancy planning

    Acetazolamide use, migraine risk and cascade testing all need specialist input before and during pregnancy.

  • Psychological distress

    Unpredictable attacks carry a real mental-health burden - low mood or anxiety deserves compassionate support.

  • Falls with injury

    Unwitnessed falls or head injuries during attacks need occupational therapy input and a safety review.

  • Paediatric onset

    Children with episodic ataxia should be seen by a specialist paediatric neurogenetics service - Great Ormond Street or regional equivalent.

Living with it

Rare, inherited, and manageable.

Four things that make the biggest difference day to day - knowing your triggers, being patient with medication, staying active and being open with your family.

A quiet reminder

Attacks are not your fault.

EA2 is a genetic channelopathy - not a lifestyle problem. Understanding triggers is about control, not blame.

  1. 01 Routine

    Know your triggers

    A simple diary of episodes, food, sleep, stress and exercise usually reveals a clear personal pattern within weeks.

  2. 02 Medicine

    Give acetazolamide time

    Most people see a meaningful drop in episode frequency within weeks - work with your specialist on dose and side effects.

  3. 03 Movement

    Stay active, but paced

    Regular gentle exercise and vestibular physiotherapy help balance without provoking attacks.

  4. 04 Family

    Talk about the genetics

    Cascade testing and genetic counselling help siblings and children make informed choices - the specialist team can guide it.

Frequently asked

Everything we get asked about EA2.

Quick answers on triggers, acetazolamide, genetics and family testing.

  • What is episodic ataxia type 2?

    A rare autosomal dominant channelopathy caused by CACNA1A mutations affecting the P/Q-type voltage-gated calcium channel. It causes recurrent episodes of ataxia, dysarthria, vertigo and nystagmus - typically lasting six to twelve hours - and is the most common of the episodic ataxias (EA1 to EA8 and beyond).

  • How is EA2 diagnosed?

    Through a careful clinical history and family history, a neurological examination looking for downbeat and gaze-evoked nystagmus, MRI brain to rule out other causes and to check for cerebellar atrophy, and CACNA1A genetic testing through a specialist commissioned neurogenetics service such as Queen Square or Cambridge.

  • What triggers episodes?

    Common triggers include emotional stress, physical exertion, alcohol, caffeine, heat, intercurrent illness, strong emotion and missed meals. Keeping a diary of episodes usually reveals a clear personal pattern - and reducing trigger exposure can cut attack frequency significantly.

  • Is acetazolamide really that effective?

    For most people, yes - acetazolamide is the best-evidenced first-line treatment and often reduces episode frequency and duration dramatically. Doses of 250 to 500 mg twice daily are typical. Side effects include paraesthesiae, altered taste, kidney stones and mild metabolic acidosis, so it is specialist prescribed and monitored.

  • How is EA2 related to migraine and SCA6?

    All three conditions are caused by different mutations in the same gene, CACNA1A. Around half of people with EA2 also have migraine, and some families show hemiplegic migraine or spinocerebellar ataxia type 6 alongside EA2 - genetic counselling helps make sense of overlapping phenotypes within a family.

  • What about my children?

    EA2 is autosomal dominant, so each child of an affected parent has a fifty per cent chance of inheriting the CACNA1A mutation. Cascade testing and reproductive options - including pre-implantation genetic diagnosis where appropriate - are offered through a specialist neurogenetics service.

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