ConditionBrain & nerves
Spinocerebellar Ataxia (SCA)
Spinocerebellar ataxias (SCAs) are a group of inherited, progressive disorders in which the cerebellum, the part of the brain that coordinates movement, and its connections slowly degenerate. They cause increasingly unsteady walking, clumsy hands, slurred speech and abnormal eye movements, usually starting in adulthood. More than 40 types are known, most passed on in an autosomal dominant pattern, so each child of an affected parent has a 50 percent chance of inheriting it. There is no cure yet, but therapy and support help people stay active and safe.
Also called: SCA, hereditary ataxia, autosomal dominant cerebellar ataxia, Machado-Joseph disease (SCA3)
At a glance
- What it is
- A group of inherited degenerative disorders of the cerebellum and its pathways.
- Inheritance
- Mostly autosomal dominant; a 50 percent chance of passing it on to each child.
- Common types
- SCA3 (Machado-Joseph disease), SCA1, SCA2, SCA6 and SCA7.
- Symptoms
- Progressive unsteady gait, poor coordination, slurred speech, abnormal eye movements, swallowing difficulty.
- Diagnosis
- Neurological examination, MRI, and genetic testing.
- Management
- Physical, occupational and speech therapy, fall prevention, symptom treatment, genetic counseling.
When to get help
Call 911 or go to the ER
- Sudden onset of severe unsteadiness, dizziness, slurred speech or double vision: call 911 or your local emergency number (possible stroke)
- Choking with breathing difficulty
See a doctor within a day or two
- Ataxia that worsens over days to weeks rather than years
- Unsteadiness with confusion and abnormal eye movements in someone who drinks heavily or is malnourished
- Coughing during meals with fever (possible aspiration pneumonia)
Book a routine appointment
- Gradually increasing clumsiness, unsteady walking or slurred speech
- A parent or sibling with ataxia, before family planning or if symptoms begin
- Falls or near-falls in someone with known ataxia
- New vision loss in someone with SCA7 or a family history of it
How SCAs affect the body
The cerebellum fine-tunes movement, balance, eye movements and speech. In SCA, nerve cells in the cerebellum and often the brainstem and spinal cord gradually die. Many SCAs are caused by an expanded repeat of three DNA letters (CAG) in a gene, producing a toxic protein. Longer repeats usually mean earlier onset and more severe disease. Repeats can lengthen when passed on, so symptoms may start earlier in each generation (anticipation).
Common types
| Type | Distinctive features |
|---|---|
| SCA1 | Ataxia with brisk reflexes, swallowing problems; progresses relatively fast |
| SCA2 | Ataxia with very slow eye movements, reduced reflexes, sometimes parkinsonism |
| SCA3 (Machado-Joseph disease) | The most common worldwide; ataxia with stiffness, dystonia, bulging eyes, neuropathy |
| SCA6 | Later onset, slowly progressive, mostly pure cerebellar ataxia; episodic vertigo |
| SCA7 | Ataxia with progressive vision loss from retinal degeneration |
| SCA17 and others | Ataxia with chorea, dementia or psychiatric symptoms |
Other inherited ataxias include Friedreich ataxia (recessive, usually starting in childhood or teens), episodic ataxia and dentatorubral-pallidoluysian atrophy.
Symptoms
Symptoms usually begin between ages 30 and 50, though some types start in childhood or late life.
- unsteady, wide-based walk and frequent falls
- poor coordination of hands, difficulty with buttons and handwriting
- slurred, slow or irregular speech
- abnormal eye movements: jerking (nystagmus), slowed movements, double vision
- swallowing difficulty and choking
- tremor when reaching
- muscle stiffness, spasms, numbness or weakness in some types
- fatigue, depression and sleep problems
- thinking and memory changes in some types
Over years to decades, many people need walking aids and later a wheelchair.
Diagnosis
- Family history: often a parent with similar symptoms, though some people have no known history.
- Neurological examination of gait, coordination, speech and eye movements.
- Brain MRI: shows shrinkage of the cerebellum and sometimes brainstem.
- Excluding acquired causes: alcohol, vitamin E or B12 deficiency, thyroid disease, celiac disease, medicines, multiple sclerosis, tumors and paraneoplastic syndromes. See cerebellar ataxia.
- Genetic testing: a blood test for the common SCA repeat expansions or a broader ataxia gene panel confirms the type.
- Genetic counseling before and after testing, especially for relatives without symptoms, because results have implications for the whole family.
Treatment and management
There is no treatment that stops or reverses SCA yet. Gene-silencing and other therapies are in clinical trials. Care aims to maintain function and safety:
- Physical therapy: balance and coordination training slows functional decline; regular exercise is important.
- Walking aids and fall prevention at home.
- Occupational therapy: adaptive tools for eating, writing and dressing.
- Speech and swallowing therapy, with diet changes to prevent choking and aspiration.
- Medicines for symptoms: for stiffness, spasms, tremor, dystonia, restless legs, depression or sleep problems. Some people with SCA6 or episodic symptoms respond to specific medicines.
- Vision support for SCA7.
- Mental health support for people and families.
- Reproductive options such as preimplantation genetic testing for those who wish to avoid passing on the gene.
Outlook
SCAs progress slowly, over 10 to 30 years or more depending on type and repeat length. Life expectancy is often reduced, mainly from swallowing problems leading to pneumonia, and falls. SCA6 tends to progress most slowly with near-normal lifespan. Joining registries and trials through ataxia organizations helps advance research.
Frequently asked questions
What is spinocerebellar ataxia?
Spinocerebellar ataxia is a group of inherited conditions in which parts of the brain controlling coordination slowly degenerate. It causes worsening balance, clumsy movements, slurred speech and eye movement problems, usually starting in adulthood.
Is spinocerebellar ataxia hereditary?
Yes. Most types are autosomal dominant, so a person with SCA has a 50 percent chance of passing it to each child. Genetic counseling helps families understand risks and decide whether to have predictive testing or use reproductive options.
What is the life expectancy with spinocerebellar ataxia?
It varies by type and age at onset. Many people live 10 to 30 years or more after symptoms begin. Some types, such as SCA6, progress slowly with near-normal lifespan. Swallowing problems and falls are the main causes of serious complications.
Is there treatment for spinocerebellar ataxia?
There is no cure yet, but physical, occupational and speech therapy help maintain independence and safety, and medicines can ease symptoms such as stiffness, tremor and sleep problems. Several disease-targeting therapies are being tested in clinical trials.
Sources
This guide was written from current patient and clinical guidance, including:
- National Institute of Neurological Disorders and Stroke: Ataxias and cerebellar or spinocerebellar degeneration
- National Ataxia Foundation: Spinocerebellar ataxia
- MedlinePlus Genetics: Spinocerebellar ataxia types
- GeneReviews (NCBI): Hereditary ataxia overview
- National Organization for Rare Disorders (NORD): Spinocerebellar ataxias