Last updated:
7/17/2025
Years published: 1989, 1997, 2004, 2011, 2014, 2017, 2025
NORD gratefully acknowledges Susan L. Perlman, MD, Clinical Professor of Neurology, Director, Ataxia Center and HD Center of Excellence, David Geffen School of Medicine, University of California Los Angeles, for assistance in the preparation of this report.
Summary
The spinocerebellar ataxias (SCA) are a group of genetic neurological disorders characterized by difficulty controlling and coordinating voluntary movements (ataxia) due to degenerative changes in the brain and spinal cord (spinocerebellar). Ataxia can lead to an awkward, uncoordinated walk (gait) often accompanied by poor eye-hand coordination, clumsiness, visual problems and abnormal speech (dysarthria).1 The spinocerebellar ataxias are slowly progressive, which means the symptoms usually worsen over time.2 The specific symptoms can vary greatly from one person to another and the age of onset and rate of the progression of these disorders can also vary greatly.2 The spinocerebellar ataxias are inherited in an autosomal dominant pattern. There are no FDA-approved therapies for these disorders. The treatments are symptomatic and supportive and designed to maximize function and reduce complications.3,4
Introduction
The classification of SCAs is complicated and has changed or evolved over time. There are approximately 50 different recognized subtypes of spinocerebellar ataxia.5,6 There are other forms of ataxia that are different from the spinocerebellar ataxias, including other inherited forms (autosomal recessive ataxia, X-linked ataxia, mitochondrial). Ataxia can also occur as a symptom of other genetic disorders including autoimmune disorders or disorders that occur because of cancer (paraneoplastic syndromes).1,4 Ataxia can also be acquired through infections, injuries, or from other external causes.1 Ataxia itself is a general term that is associated with numerous different disorders.
Because of the small number of people diagnosed with specific SCA subtypes and the overall lack of knowledge about many of the subtypes, detailed descriptions of most of these disorders are not available. As more people are identified with these conditions, a better clinical understanding of the different subtypes will come to be known.
There are approximately 50 subtypes of spinocerebellar ataxia, and the overall symptoms and severity of these disorders vary greatly, but ataxia is the main symptom.5,6,7
Ataxia results in people having difficulty controlling and coordinating their voluntary movements.2,8 Affected individuals may have difficulty walking and maintaining their balance. They may walk in an awkward, clumsy or unsteady manner. Eventually, they may have difficulty standing and may have frequent falls.2,9 They may have a tremor in their legs.2,3 Ataxia is a progressive condition, which means the symptoms may start out mild and get progressively worse; the rate of progression will vary from one person to another. Some people may only develop mild complications while others develop more serious ones.2
Some people may have trouble with their speech, including having slowed or slurred speech (dysarthria) because the muscles that control speech are weakened and hard to control. Some people may have trouble swallowing properly (dysphagia) and may have unexpected choking.3
Affected people may also have double vision (diplopia), difficulty focusing their eyes and unwanted eye movements such as rapid, involuntary eye movements (nystagmus).2,8 Some people may have cognitive issues including difficulty thinking, remembering, or concentrating.2,10
There are additional symptoms associated with specific forms of spinocerebellar ataxia. The chart below shows the specific subtype and commonly associated symptoms. However, many of these subtypes have only been reported in one family, one person, or a small group of people and the specific symptoms associated with a specific subtype may evolve over time as more individuals are diagnosed with each subtype. The information in the chart is from multiple sources.3,10-13
| Spinocerebellar Ataxia Subtype | Additional Symptoms |
| SCA 1 | Tremors; weakness, numbness and tingling of the hands and feet (peripheral neuropathy); weakness or paralysis of certain eye muscles (ophthalmoplegia) |
| SCA2 | Slow, irregular eye movements when changing focus from one point to another (slow saccades); signs and symptoms similar to Parkinson’s disease (parkinsonism); twitching or jerking of the muscles (myoclonus); dementia |
| SCA3; Machado-Joseph disease | Slow, irregular eye movements when changing focus from one point to another (slow saccades); persistent stare; weakness, numbness and tingling of the hands and feet (peripheral neuropathy); tremors; repetitive, involuntary eye movements (nystagmus) |
| SCA4 | Affects the sensory nerves which frequently leads to loss of feeling (sensation) in the hands and feet (sensory neuropathy) |
| SCA5 | Early onset; slow progression |
| SCA6 | Very slow course; often mild; usually adult onset |
| SCA7 | Degeneration of the nerve-rich membrane that lines the back of the eyes (retina); vision loss |
| SCA8 | Often mild |
| SCA9 – unassigned | N/A |
| SCA10 | Seizures; involuntary muscle twitching (fasciculations) |
| SCA11 | Often mild |
| SCA12 | Tremor; dementia |
| SCA13 | Cognitive impairment; intellectual disability |
| SCA14 | Slow disease progression |
| SCA15; SCA16; formerly SCA16 | Slow disease progression; twitching or jerking of the muscles (myoclonus); involuntary, sustained muscle spasms (dystonia) |
| SCA17 | Cognitive impairment; seizures; dementia |
| SCA18 | Highly arched feet (pes cavus); repetitive, involuntary eye movements (nystagmus) |
| SCA19; SCA22 | Repetitive, involuntary eye movements (nystagmus); hand tremor; cognitive impairment; twitching or jerking of the muscles (myoclonus) |
| SCA20 | Early speech difficulties; slowness of movements (bradykinesia); involuntary movements of the soft palate (palatal tremor) |
| SCA21 | Mild to severe cognitive impairment |
| SCA23 | Inability to sense touch, pain, temperature, or vibration in the hands or feet |
| SCA24; Spinocerebellar ataxia autosomal recessive 4 | Autosomal recessive inheritance; reclassified as SCAR4 |
| SCA25 | Affects the sensory nerves, which frequently leads to loss of feeling (sensation) in the hands and feet; facial tics; hearing loss; gastrointestinal problems |
| SCA26 | Repetitive, involuntary eye movements (nystagmus) |
| SCA27A | Cognitive impairment; early onset hand tremor; involuntary, repetitive movements of the mouth, face, and tongue (orofacial dyskinesia) |
| SCA27B | Late onset form that is prevalent in older adults |
| SCA28 | Weakness or paralysis of certain eye muscles (ophthalmoplegia); droopy upper eyelid (ptosis) |
| SCA29 | Early onset form; slow or nonprogressive |
| SCA30 | Slowly progressive form |
| SCA31 | Hearing loss; vertigo; usually late onset |
| SCA32 | Cognitive impairment; male infertility |
| SCA33 – not assigned | N/A |
| SCA34 | Skin lesions; repetitive, involuntary eye movements (nystagmus) |
| SCA35 | Late onset; slowly progressive |
| SCA36 | Hearing loss; weakness of the tongue (tongue atrophy) |
| SCA37 | Skin lesions; repetitive, involuntary eye movements (nystagmus); abnormal vertical eye movements; slowly progressive |
| SCA38 | Adult onset; slowly progressive |
| SCA39 – not assigned | N/A |
| SCA40 | Overresponsive reflexes (hyperreflexia); tremor; signs and symptoms similar to Parkinson’s disease (parkinsonism); muscle weakness and muscle tightness (spasticity) |
| SCA41 | Adult onset |
| SCA42 | Variable age of onset; repetitive, involuntary eye movements (nystagmus) |
| SCA43 | Adult onset; slowly progressive |
| SCA44 | Inability to control the speed, distance, and range of movement (dysmetria) |
| SCA45 | Repetitive, involuntary eye movements (nystagmus) |
| SCA46 | Affects the sensory nerves, which frequently leads to loss of feeling (sensation) in the hands and feet; slow, irregular eye movements when changing focus from one point to another (slow saccades); repetitive, involuntary eye movements (nystagmus) |
| SCA47 | Reclassified as SCA27B or Paddas syndrome |
| SCA48 | Cognitive dysfunction; abnormal eye movements |
| SCA49 | Variable age of onset; slowly progressive |
| SCA50 | Adult onset; hearing loss; defect in side-to-side eye movements (oculomotor apraxia) |
| SCA51 | Variable age of onset; repetitive, involuntary eye movements (nystagmus) |
The spinocerebellar ataxias are caused by changes (variants) in specific genes. Genes provide instructions for creating proteins that play a critical role in many functions of the body. When a variant in a gene occurs, the protein product may be faulty, inefficient, absent, or overproduced.14 Depending upon the functions of the protein, this can affect many organ systems of the body, including the brain.
For many subtypes of spinocerebellar ataxia, the specific causal gene has been identified. However, for some of these disorders, the causal gene is unknown. For example, SCA type 1 is caused by variants in the ATXN1 gene; SCA type 2 is caused by variants in the ATXN2 gene, SCA type 3 is caused by variants in the ATXN3 gene; and SCA type 4 is caused by variants in ZFHX3 gene.15 Online Mendelian Inheritance in Man (OMIM) 15 is an online resource that includes information about the genes associated with specific genetic disorders (if known) and includes information on the various forms of spinocerebellar ataxia.
Inheritance
Spinocerebellar ataxias are inherited in an autosomal dominant manner. Dominant genetic disorders occur when only a single copy of a disease-causing gene variant is necessary to cause the disease. The gene variant can be inherited from either parent or can be the result of a new (de novo) changed gene in the affected individual that is not inherited. The risk of passing the gene variant from an affected parent to a child is 50% for each pregnancy. The risk is the same for males and females.
In some forms of spinocerebellar ataxia, genetic anticipation may occur.2,8 This means that the disorder may be more severe, and the signs and symptoms may develop earlier in life as the disorder is passed on with each successive generation.2,8
Spinocerebellar ataxia affects both males and females and depending on the specific subtype, can affect children or adults. Some of these disorders are more common in certain ethnic groups.10 The exact number of people who have these disorders is unknown. Rare disorders like spinocerebellar ataxia often go misdiagnosed or undiagnosed, making it difficult to determine their true frequency in the general population. Estimates in the medical literature generally suggest that at least 1-5 in 100,000 people in the general population have spinocerebellar ataxia.8,10 Spinocerebellar ataxia subtypes 1, 2, 3, and 6 are considered the most common worldwide.5
A diagnosis of spinocerebellar ataxia may be suspected based upon the identification of characteristic symptoms (especially an impaired or awkward gait), a detailed patient and family history 2,3 and a thorough clinical evaluation including specific tests.3
Molecular genetic testing can confirm a diagnosis of certain forms of spinocerebellar ataxia. Molecular genetic testing can detect variants in specific genes known to cause these disorders but is not available for all forms of spinocerebellar ataxia. Genetic testing is the most efficient and definitive way to obtain a diagnosis.8,11
A variety of specialized tests may show degeneration of the cerebellum (cerebellar atrophy) or other brain structures. Such imaging techniques may include computerized tomography (CT) scanning and magnetic resonance imaging (MRI).2,19 During CT scanning, a computer and X-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of organs and bodily tissues. The cerebellum is the part of the brain that plays a role in coordinating voluntary movements and balance.
Rating Systems
Neurological disorders often have rating scales that doctors use to assess the symptoms, progression and severity of a disorder. For ataxia, these systems generally measure gait, stance and speech. One system is known as the functional scale for the assessment and rating of ataxia (f-SARA). It was developed to measure the clinical effectiveness of therapies studied in clinical trials for spinocerebellar ataxia.4-5,7,21 Another commonly used scale for rating ataxia is the International Cooperative Ataxia Rating Scale (ICARS).4 These rating systems can be used to set a baseline for people when they are diagnosed with ataxia.3
Experts have designed a rating scale for Friedreich’s ataxia that has also shown value in assessing patients with spinocerebellar ataxia.6,22 This rating system evaluates how people are managing activities of daily living such as buttoning a shirt, standing up, or eating or drinking.6,22 It assists doctors in assessing the severity and progression of the disorder. This system is called the Friedreich Ataxia Rating Scale – Activities of Daily Living (FARS-ADL).
Another newer rating system called Spinocerebellar Ataxia Composite Scale (SCACOMS) has been developed to help assess disease progression and treatment effectiveness.23 A recent evaluation of this rating system suggests that the tool can be useful for capturing disease progression and highlighting treatment effects.23
Treatment
There are no curative treatments for spinocerebellar ataxia or treatments that slow the disease progression.2,8 Most treatment is typically supportive24 and directed toward the specific symptoms that are apparent in each person.8 Treatment may require the coordinated efforts of a team of specialists. Depending on the specific factors (age of onset, specific symptoms, rate of progression), consultations with different specialists may be necessary. This can include pediatricians, specialists in the diagnosis and treatment of neurological disorders (neurologists), specialists in the diagnosing and treatment of communication and swallowing disorders (speech pathologists), specialists in the diagnosis and treatment of eye disorders (ophthalmologists), specialists in the diagnosis and treatment of the gastrointestinal tract (gastroenterologists) and other healthcare professionals.3
The specific therapeutic procedures and interventions for people with a spinocerebellar ataxia will vary depending upon numerous factors including the specific symptoms, severity of the disorder, the person’s age and overall health and tolerance to certain medications or procedures.
Most therapies are supportive and are designed to help people remain active. These therapies can include walking aids like canes, walkers, wheelchairs and crutches to help with coordination and balance. Physical therapy can help people maintain strength and movement and help people manage gait and balance problems.2,7,11 In mild stages of ataxia, physical therapy can lead to significant improvement in balance and gait.8 Occupational therapy can also be important to manage symptoms, maintain function and improve quality of life.7,11 Speech therapy can help with communication and lower the risk of choking (aspiration).11 Modifying the consistency of food can help people at risk of aspiration.3 Speech and swallowing difficulties can be treated with certain medications.2 For individuals with severe speech difficulties, assistive devices such as computer devices can be beneficial.2,8
Special glasses can be helpful to reduce double vision or blurred vision.2 Eye surgery may be recommended for some individuals.
Muscle spasms and spasticity can be treated with medications including baclofen, tizanidine and dantrolene.3
Genetic counseling is recommended for affected individuals and their families. 3,11 Psychosocial supportive services for the entire family are essential as well.3,25
Riluzole is a medication that has been studied for the treatment of spinocerebellar ataxia. In SCA due to specific causes, it may be effective in the short-term26 and improve speech and gait.4 Riluzole is not yet approved by the U.S. Food and Drug Administration (FDA) for the treatment of spinocerebellar ataxia and more study is required. Treatment with riluzole requires monitoring of liver enzymes because of the risk of liver damage.4,7,26
As of June 2025, a modified form of riluzole (troriluzole) is currently being evaluated by the FDA as a potential treatment for all types of SCA.
There are several different medications being studied for spinocerebellar ataxia including gene directed therapies. For some of these medications, effectiveness is being measured using rating systems such as f-SARA and FARS-ADL.6,24 Additional medications have been studied in the past that have achieved inconsistent results or shown small improvements26 but required further study or support.4,7
Acetazolamide is a medication that has shown some effectiveness in treatment of a specific form of spinocerebellar ataxia due to variants in the CACNA1A gene (SCA6). A small trial demonstrated improvement of some affected individuals using the ataxia rating systems.4 More research is necessary to determine the long-effectiveness and safety of this drug for this form of spinocerebellar ataxia.
Studies have been conducted or are ongoing on various neuromodulation techniques to treat spinocerebellar ataxia. Neuromodulation acts directly on the nervous system usually through the delivery of electrical currents or medications. Neuromodulation has shown promising results4 in some individuals. Transcranial magnetic stimulation (TMS),26-28 transcranial direct current stimulation (tDCS) and deep brain stimulation have been studied as a treatment for people with spinocerebellar ataxia.4
Hematopoietic stem cell transplantation is also being studied as a treatment for people with spinocerebellar ataxia.29
Information on current clinical trials is posted on the Internet at https://clinicaltrials.gov/. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Toll-free: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/for-patients-and-families/information-resources/info-clinical-trials-and-research-studies/
For information about clinical trials sponsored by private sources, contact:
https://www.centerwatch.com/
For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/
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The Genetic and Rare Diseases Information Center (GARD) has information and resources for patients, caregivers, and families that may be helpful before and after diagnosis of this condition. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), part of the National Institutes of Health (NIH).
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View reportOnline Mendelian Inheritance In Man (OMIM) has a summary of published research about this condition and includes references from the medical literature. The summary contains medical and scientific terms, so we encourage you to share and discuss this information with your doctor. OMIM is authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine.
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