View source for Spinocerebellar ataxia

{{Infobox_Disease |
  Name           = {{PAGENAME}} |
  Image          = brain-cerebellum.png |
  Caption        = Cerebellum (in blue) of the human brain |
  DiseasesDB     = 12339 |
  ICD10          = {{ICD10|G|11||g|10}} |
  ICD9           = {{ICD9|334}} |
  ICDO           = |
  OMIM           = |
  MedlinePlus    = |
  eMedicineSubj  = |
  eMedicineTopic = |
  MeshID         = D020754 |
}}
{{SI}}
{{CMG}}

==Overview==
'''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 (SCA) is one of a group of [[genetic disorder]]s characterized by slowly progressive incoordination of [[Gait (human)|gait]] and often associated with poor coordination of hands, speech, and eye movements. Frequently, [[atrophy]] of the [[cerebellum]] occurs. <ref>[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowSection&rid=gnd.section.218 Genes and Disease at nlm.nih.gov] - Gives a concise description of SCA, along with a picture of shrunken degenerated cerebellum.</ref>

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 [[symptom]]s.

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

==Treatment and prognosis==
There is no known cure for spinocerebellar ataxia, which is a progressive disease (it gets worse with time), although not all types cause equally severe disability.  

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 may need assistance to perform daily tasks. 

The treatment of incoordination or ataxia, then mostly involves the use of adaptive devices to allow the ataxic individual to maintain as much independence as possible. Such devices may include a cane, crutches, walker, or wheelchair for those with impaired gait; devices to assist with writing, feeding, and self care if hand and arm coordination are impaired; and communication devices for those with impaired speech.

Many patients with hereditary or idiopathic forms of ataxia have other symptoms in addition to ataxia. Medications or other therapies might be appropriate for some of these symptoms, which could include tremor, stiffness, depression, spasticity, and [[sleep disorder]]s, among others.

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 may lead to an earlier onset and a more radical progression of clinical symptoms.

==Diagnosis==
It can be easily misdiagnosed as another [[neurology|neurological]] condition, such as [[multiple sclerosis]] (MS). 

One means of identifying the disease is with an [[magnetic resonance imaging|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 29 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 are 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 disease]]s.

{| class="wikitable"
!SCA Type
!Average Onset<br>(Range in Years)
!Average Duration<br>(Range in Years)
!What the patient experiences
!Common origin
!Problems<br>with [[DNA]]
|-
|SCA1<ref>{{GeneTests|sca1}}</ref> ([[ATXN1]])
|4th decade<br>(<10 to >60)
|15 years<br>(10-28)
|Hypermetric [[saccades]], slow saccades, [[upper motor neuron]]<br>(note: saccades relates to eye movement)
|&nbsp; 
|CAG [[Repeated sequence (DNA)|repeat]], 6p ([[Ataxin 1]])
|-
|SCA2<ref>{{GeneTests|sca2}}</ref> ([[ATXN2]])
|3rd - 4th decade<br>(<10 to >60)
|10 years<br>(1-30)
|Diminished velocity saccades<br>'''areflexia''' (absence of [[neurologic]] [[reflexes]])
|Cuba 
|CAG [[Repeated sequence (DNA)|repeat]], 12q
|-
|SCA3<ref>{{GeneTests|sca3}}</ref> (MJD) ([[ATXN3]])
|4th decade<br>(10-70)
|10 years<br>(1-20)
|Also called [[Machado-Joseph disease]] (MJD)<ref>{{NINDS|machado_joseph}}</ref><br>Gaze-evoked [[nystagmus]] (a rapid, involuntary, [[oscillation|oscillatory]] [[motion (physics)| motion]] of the eyeball)<br>[[upper motor neuron]]<br>slow saccades
|Azores<br>(Portugal) 
|CAG [[Repeated sequence (DNA)|repeat]], 14q
|-
|SCA4 ([[PLEKHG4]])
|4th - 7th decade<br>(19-72)
|Decades
|'''areflexia''' (absence of [[neurologic]] [[reflexes]])
|&nbsp; 
|[[Chromosome]] 16q
|-
|SCA5 ([[SPTBN2]])
|3rd - 4th decade<br>(10-68)
|>25 years
|Pure [[Cerebellum|cerebellar]]
|&nbsp; 
|[[Chromosome]] 11
|-
|[[Spinocerebellar ataxia type-6|SCA6]]<ref>{{GeneTests|sca6}}</ref> ([[CACNA1A]])
|5th - 6th decade<br>(19-71)
|>25 years
|Downbeating [[nystagmus]], positional [[Vertigo_(medical)|vertigo]]<br>[[Symptoms]] can appear for the first time as late as 65 years old.
|&nbsp; 
|CAG [[Repeated sequence (DNA)|repeat]], 19p<br>[[Calcium]] channel [[gene]]
|-
|SCA7<ref>{{GeneTests|sca7}}</ref> ([[ATXN7]])
|3rd - 4th decade<br>(0.5 - 60)
|20 years<br>(1-45; early onset correlates with shorter duration)
|[[Macular degeneration]], [[upper motor neuron]], slow saccades
|&nbsp; 
|CAG [[Repeated sequence (DNA)|repeat]], 3p  ([[Ataxin 7]])
|-
|SCA8<ref>{{GeneTests|sca8}}</ref> ([[IOSCA]])
|39 yrs<br>(18-65)
|Normal lifespan
|Horizontal [[nystagmus]] (a rapid, involuntary, [[oscillation|oscillatory]] motion of the [[eyeball]])
|&nbsp; 
|CTG [[Repeated sequence (DNA)|repeat]], 13q
|-
|SCA10<ref>{{GeneTests|sca10}}</ref> ([[ATXN10]])
|36 years
|9 years
|[[ataxia]], [[seizure]]s
|Mexico 
|[[Chromosome]] 22q linked<br>pentanucleotide [[Repeated sequence (DNA)|repeat]]
|-
|[[SCA11]]
|30 yrs<br>(15-70)
|Normal lifespan
|Mild, remain [[Wiktionary:ambulatory|ambulatory]] (able to walk about on one's own)
|&nbsp;
|15q
|-
|SCA12<ref>{{GeneTests|sca12}}</ref> ([[PPP2R2B]])
|33 yrs<br>(8-55)
|&nbsp;
|[[Head]] and [[hand]] [[tremor]],<br>[[akinesia]] (loss of normal motor function, resulting in impaired [[muscle]] movement)
|&nbsp; 
|CAG [[Repeated sequence (DNA)|repeat]], 5q
|-
|[[Spinocerebellar ataxia type-13|SCA13]]
|Childhood or adulthood depending on mutation
|Depending on [[KCNC3]] (a kind of gene)
|[[Mental retardation]]
|&nbsp; 
|19q
|-
|SCA14<ref>{{GeneTests|sca14}}</ref> ([[PRKCG]])
|28 yrs<br>(12-42)
|Decades<br>(1-30)
|[[Myoclonus]] (a sudden [[muscle contraction|twitching]] of [[muscle]]s or parts of muscles, without any rhythm or pattern, occurring in various [[brain]] disorders)
|&nbsp; 
|19q
|-
|[[SCA16]]
|39 yrs<br>(20-66) 
|1-40 years 
|[[Head]] and [[hand]] [[tremor]]
|&nbsp; 
|8q
|-
|SCA17 ([[TATA binding protein|TBP]])
|&nbsp; 
|&nbsp; 
|&nbsp; 
|&nbsp; 
|CAG [[Repeated sequence (DNA)|repeat]], 6q (TATA-binding protein)
|-
|SCA19, SCA22
|&nbsp;
|&nbsp;
|Mild [[cerebellum|cerebellar]] [[syndrome]], [[dysarthria]]
|&nbsp;
|&nbsp;
|-
|SCA25
|1.5-39 yrs 
|Unknown 
|[[ataxia]] with [[sense|sensory]] [[neuropathy]], [[vomiting]] and [[gastrointestinal tract|gastrointestinal]] [[pain]].
|&nbsp; 
|2p
|}

Others include SCA18, SCA20, SCA21, SCA23, SCA26, SCA28, and SCA29.

Four X-linked types have been described ({{OMIM2|302500}}, {{OMIM2|302600}}, {{OMIM2|301790}}, {{OMIM2|301840}}), but only the first of these has so far been tied to a gene (SCAX1).

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

* Numerous types of ''autosomal dominant'' cerebellar ataxias are now known for which specific genetic information is available. Synonyms for autosomal dominant cerebellar 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 is a prominent feature: [[Friedreich ataxia]], [[ataxia-telangiectasia]], ataxia with vitamin E deficiency, ataxia with oculomotor apraxia (AOA), [[spastic ataxia]]. Disorder Subdivisions: Friedreich's ataxia, Spinocerebellar ataxia, Ataxia telangiectasia, Vasomotor ataxia, Vestibulocerebellar, Ataxiadynamia, Ataxiophemia, Olivopontocerebellar atrophy, and [[Charcot-Marie-Tooth disease]].

<gallery>
Image:Autodominant.jpg|There are numerous types of [[autosomal dominant]] cerebellar ataxias
Image:autorecessive.jpg|There are five typical [[Recessive gene|autosomal recessive]] disorders in which ataxia is a prominent feature
</gallery>

==References==
<references/>

==External links==
*http://www.ataxia.org - National Ataxia Foundation is dedicated to helping families with ataxia through research, education, and support.
*[http://www.tchain.com/otoneurology/disorders/central/cerebellar/sca.htm Cerebellar Degenerations at tchain.com]
* http://leedsdna.info/tests/DRPLA.htm 
* http://www.ataxiaforums.co.uk
*[http://wiki.d-addicts.com/Ichi_Rittoru_no_Namida Ichi Rittoru no Namida (One Litre of Tears)] - A Japanese drama based on the true story of a girl who suffered from Spinocerebellar ataxia.
*[http://www.cureataxia.org CureAtaxia.org] - One Chicago family's fight against SCA Type 1 Ataxia
<br/>
*{{OMIM3|183090}} {{RareDiseases|4071|Spinocerebellar ataxia 1}}
*{{OMIM3|164400}} {{RareDiseases|4072|Spinocerebellar ataxia 2}}
**{{NINDS|ataxia}}
**{{NINDS|msa}}
**{{NINDS|opca_doc}}
**{{MedlinePlus|000758|Olivopontocerebellar atrophy}}

*{{OMIM3|607317}} {{RareDiseases|4952|Spinocerebellar ataxia, autosomal recessive 4}}
*{{OMIM3|600224}} {{RareDiseases|4953|Spinocerebellar ataxia 5}}
*{{OMIM3|605259}} {{RareDiseases|9611|Spinocerebellar ataxia 13}}
*{{OMIM3|117360}} {{RareDiseases|9975|Spinocerebellar ataxia 30}}
*{{OMIM3|608703}} {{RareDiseases|9996|Spinocerebellar ataxia 25}}
*{{OMIM3|600223}} {{RareDiseases|9970|Spinocerebellar ataxia 4}}
*{{OMIM3|606002}} {{RareDiseases|4949|Spinocerebellar ataxia, autosomal recessive 1}}
*{{OMIM3|271250}} {{RareDiseases|9971|Spinocerebellar ataxia, autosomal recessive 3}}
*{{OMIM3|609306}} {{RareDiseases|9995|Spinocerebellar ataxia 26}}
*{{OMIM3|608029}} {{RareDiseases|4954|Spinocerebellar ataxia, autosomal recessive 6}}
*{{OMIM3|607346}} {{RareDiseases|9969|Spinocerebellar ataxia 19}}
*{{OMIM3|608687}} {{RareDiseases|9997|Spinocerebellar ataxia 20}}
*{{OMIM3|302600}} {{RareDiseases|9978|Spinocerebellar ataxia, X-linked, 2}}
*{{OMIM3|606937}} {{RareDiseases|9977|Spinocerebellar ataxia, autosomal recessive 5}}
*{{OMIM3|301840}} {{RareDiseases|9980|Spinocerebellar ataxia, X-linked, 4}}
*{{OMIM3|301790}} {{RareDiseases|9981|Spinocerebellar ataxia, X-linked, 3}}
*{{OMIM3|109150}} {{RareDiseases|6801|Spinocerebellar ataxia 3; Machado Joseph disease}}
**{{NINDS|machado_joseph/detail_machado_joseph.htm}}
*{{OMIM3|607458}} {{RareDiseases|9976|Spinocerebellar ataxia 18}}
*{{RareDiseases|9963|Spinocerebellar ataxia 27}}
*{{OMIM3|164500}} {{RareDiseases|4955|Spinocerebellar ataxia 7}}
*{{OMIM3|607454}} {{RareDiseases|9999|Spinocerebellar ataxia 99}}
*{{OMIM3|610245}} {{RareDiseases|9950|Spinocerebellar ataxia 23}}
*{{OMIM3|610246}} {{RareDiseases|9951|Spinocerebellar ataxia 28}}
*{{OMIM3|603680}} {{RareDiseases|4956|Spinocerebellar ataxia 8}}
*{{OMIM3|607250}} {{RareDiseases|10000|Spinocerebellar ataxia, autosomal recessive, with axonal neuropathy}}
*{{OMIM3|605361}} {{RareDiseases|4062|Infantile onset Spinocerebellar ataxia}}
*{{OMIM3|271245}} {{RareDiseases|4957|Spinocerebellar ataxia amyotrophy deafness}}
*{{RareDiseases|4958|Spinocerebellar ataxia dysmorphism}}
*{{OMIM3|301310}} {{RareDiseases|668|Anemia, sideroblastic spinocerebellar ataxia; Pagon Bird Detter syndrome}}
*{{OMIM3|229300}} {{RareDiseases|6468|Friedreich's ataxia; Spinocerebellar ataxia, Friedreich}}

{{Diseases of the nervous system}}
{{Trinucleotide repeat disorders}}


[[Category:Disability]]
[[Category:Genetic_disorders]]
[[Category:Neurological disorders]]

[[de:Spinozerebelläre Ataxie]]
[[fr:Ataxie spinocérébelleuse]]
[[it:Atassia spinocerebellare]]
[[ja:脊髄小脳変性症]]
[[pl:Ataksja rdzeniowo-móżdżkowa]]
[[pt:Degeneração Espinocerebelar]]
[[th:สไปโนซีรีเบลลาร์อะแท็กเซีย]]
[[zh:小腦萎縮症]]

{{WH}}
{{WS}}