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Spinocerebellar ataxia (SCA) is a genetic disease with multiple types, each of which could be considered a disease in its own right.

Symptoms

Spinocerebellar ataxia is one of a group of genetic disorders characterized by slowly progressive in coordination of gait and often associated with poor coordination of hands, speech, and eye movements. Frequently, atrophy of the cerebellum occurs.

As with other forms of ataxia, SCA results in unsteady and clumsy motion of the body due to a failure of the fine coordination of muscle movements, along with other symptoms.

The symptoms of the condition vary with the specific type (there are several), and with the individual patient. Generally, a sufferer retains full mental capacity but may progressively lose physical control.

Treatment and prognosis

There is no known cure for this degenerative condition, which lasts for the remainder of the sufferer’s life.

Treatments are generally limited to softening symptoms, not the disease itself. The condition can be irreversible. A person with this disease will usually end up needing to use a wheelchair, and eventually they will need assistance to perform daily tasks.

Both onset of initial symptoms and duration of disease can be subject to variation. If the disease is caused by a polyglutamine trinucleotide repeat CAG expansion, a longer expansion will lead to an earlier onset and a more radical progression of clinical symptoms, resulting in earlier death.

Diagnosis

It can be easily misdiagnosed as another neurological condition, such as multiple sclerosis (MS).

One means of identifying the disease is with an MRI to view the brain. Once the disease has progressed sufficiently, the cerebellum (a part of the brain) can be seen to have visibly shrunk. The most precise means of identifying SCA, including the specific type, is through DNA analysis. Some, but far from all, types of SCA may be inherited, so a DNA test may be done on the children of a sufferer, to see if they are at risk of developing the condition.

SCA is related to olivopontocerebellar atrophy (OPCA); SCA types 1, 2, and 7 are also types of OPCA. However, not all types of OPCA are types of SCA, and vice versa. This overlapping classification system is both confusing and controversial to some in this field.

Types

The following is a list of some, not all, types of spinocerebellar ataxia. The first ataxia gene was identified in 1993 for a dominantly inherited type. It was called “Spinocerebellar ataxia type 1″ (SCA1). Subsequently, as additional dominant genes were found they were called SCA2, SCA3, etc. Usually, the “type” number of “SCA” refers to the order in which the gene was found. At this time, there are at least 28 different gene mutations which have been found (not all listed).

Identifying the different types of SCA now requires knowledge of the normal genetic code, and faults in this code, which is contained in a person’s DNA (Deoxyribonucleic acid). The “CAG” mentioned below is one of many three-letter sequences that makes up the genetic code, this specific one coding the amino acid glutamine. Thus, those ataxias with poly CAG expansions, along with several other neurodegenerative diseases resulting from a poly CAG expansion, are referred to as polyglutamine diseases.

Inheritance

The hereditary ataxias are categorized by mode of inheritance and causative gene or chromosomal locus. The hereditary ataxias can be inherited in an autosomal dominant, autosomal recessive, or X-linked manner.

Numerous types of autosomal dominant cerebella ataxias are now known for which specific genetic information is available. Synonyms for autosomal dominant cerebella ataxias (ADCA) used prior to the current understanding of the molecular genetics were Marie’s ataxia, inherited olivopontocerebellar atrophy, cerebello-olivary atrophy, or the more generic term “Spinocerebellar degeneration.” (Spinocerebellar degeneration is a rare inherited neurological disorder of the central nervous system characterized by the slow degeneration of certain areas of the brain. There are three forms of Spinocerebellar degeneration: Types 1, 2, 3. Symptoms begin during adulthood.)

There are five typical autosomal recessive disorders in which ataxia are a prominent feature: Friedreich ataxia, ataxia-telangiectasia, ataxia with vitamin E deficiency, ataxia with coulometer paraxial, spastic ataxia. Disorder Subdivisions: Friedreich’s ataxia, Marie’s ataxia, Ataxia telangiectasia, vasomotor ataxia, Vestibulo cerebellar, Ataxiadynamia, Ataxiophemia, Olivopontocerebellar atrophy, and Charcot-Marie-Tooth disease.

Medical

• Genes and Disease - Gives a concise description of SCA, along with a picture of shrunken degenerated cerebellum.
• Rehab Network web site - Detailed description of SCA.
• Cerebella Degenerations
• Hereditary ataxia overview
• NINDS machado_joseph
• DRPLA - Dentatorubropallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder characterised by myoclonus, epilepsy, cerebella ataxia, choreoathetosis and dementia.