Classification A few<unk> s remain unspecified and can not be precisely diagnosed, but in the last decade genetic testing has allowed precise identification of dozens of different<unk> s and more tests are being added each year. In 2008, a genetic ataxia blood test developed to test for 12 types of<unk> , Friedreich's ataxia, and several others. However, since not every<unk>  has been genetically identified some<unk> s are still diagnosed by neurological examination, which may include a physical exam, family history, MRI<unk> nning of the brain and spine, and spinal tap. Many<unk> s below fall under the category of polyglutamine diseases, which are caused when a disease-associated protein (i.e., ataxin-1, ataxin-3, etc.) contains a large number of repeats of glutamine residues, termed a polyQ sequence or a "CAG trinucleotide repeat" disease for either the one-letter designation or codon for glutamine respectively. The threshold for symptoms in most forms of<unk>  is around 35, though for<unk> 3 it extends beyond 50. Most polyglutamine diseases are dominant due to the interactions of resulting polyQ tail. The first ataxia gene was identified in 1993 and called<unk>  type 1" <unk> 1); later genes were called<unk> 2,<unk> 3, 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 that have been found. The following is a list of some of the many types of<unk> .<unk>  Type Average Onset(Range in Years) Average Duration(Range in Years) What the patient experiences Common origin Problemswith DNA<unk> 1 (ATXN1) 4th decade(60) 15 years(10–35) Hypermetric saccades, slow saccades, upper motor neuron(note: saccades relates to eye movement) CAG repeat, 6p (Ataxin 1)<unk> 2 (ATXN2) 3rd–4th decade(60) 10 years(1–30) Diminished velocity saccadesareflexia (absence of neurologic reflexes) Cuba CAG repeat, 12q<unk> 3 (MJD) (ATXN3) 4th decade(10–70) 10 years(1–20) Also called Machado-Joseph disease (MJD)Gaze-evoked nystagmus (a rapid, involuntary, oscillatory motion of the eyeball)upper motor neuronslow saccades Azores(Portugal) CAG repeat, 14q<unk> 4 (PLEKHG4) 4th–7th decade(19–72) Decades areflexia (absence of neurologic reflexes) Chromosome 16q<unk> 5 (SPTBN2) 3rd–4th decade(10–68) >25 years Pure cerebellar Chromosome 11<unk> 6 (CACNA1A) 5th–6th decade(19–71) >25 years Downbeating nystagmus, positional vertigoSymptoms can appear for the first time as late as 65 years old. CAG repeat, 19pCalcium channel gene<unk> 7 (ATXN7) 3rd–4th decade(0.5–60) 20 years(1–45; early onset correlates with shorter duration) Macular degeneration, upper motor neuron, slow saccades CAG repeat, 3p (Ataxin 7)<unk> 8 (IOSCA) 39 yrs(18–65) Normal lifespan Horizontal nystagmus (a rapid, involuntary, oscillatory motion of the eyeball), instability, lack of coordination CTG repeat, 13q<unk> 10 (ATXN10) 36 years 9 years ataxia, seizures Mexico Chromosome 22q linkedpentanucleotide repeat<unk> 11 (TTBK2) 30 yrs(15–70) Normal lifespan Mild, remain ambulatory (able to walk about on one's own) 15q<unk> 12 (PPP2R2B) 33 yrs(8–55) Head and hand tremor,akinesia (loss of normal motor function, resulting in impaired muscle movement) CAG repeat, 5q<unk> 13 (KCNC3) Childhood or adulthood depending on mutation Depending on KCNC3 (a kind of gene) Mental retardation 19q<unk> 14 (PRKCG) 28 yrs(12–42) Decades(1–30) Myoclonus (a sudden twitching of muscles or parts of muscles, without any rhythm or pattern, occurring in various brain disorders) 19q<unk> 16 (ITPR1) 39 yrs(20–66) 1–40 years Head and hand tremor 8q<unk> 17 (TBP) CAG repeat, 6q (TATA-binding protein)<unk> 19,<unk> 22 (KCND3) Mild cerebellar syndrome, dysarthria<unk> 25 1.5–39 yrs Unknown ataxia with sensory neuropathy, vomiting and gastrointestinal pain. 2p<unk> 27 (FGF14) 15–20 yrs Unknown ataxia with poor cognition, dyskinesias and tremor. FGF14 13q34<unk> 35 40–48 years Unknown gait and limb ataxia, dysarthria, ocular dysmetria, intention tremor, pseudobulbar palsy, spasmodic torticollis, extensor plantar responses, reduced proprioception and hyperreflexia China transglutaminase 6 (TGM6) located at chromosome 20p13 Others include<unk> 18,<unk> 20,<unk> 21,<unk> 23,<unk> 26,<unk> 28, and<unk> 29. Four X-linked types have been described (, , , ), but only the first of these has so far been tied to a gene <unk> X1). Name OMIM RareDiseases Other Anemia, sideroblastic<unk> ; Pagon Bird Detter syndrome Friedreich's ataxia;<unk> , Friedreich Infantile onset<unk> <unk>  1<unk>  2<unk>  3; Machado Joseph disease<unk>  4<unk>  5<unk>  7<unk>  8<unk>  13<unk>  18<unk>  19<unk>  20<unk>  21<unk>  23<unk>  25<unk>  26<unk>  28<unk>  30<unk>  35<unk>  amyotrophy deafness syndrome ORPHA:2074 at Orphanet<unk> , autosomal recessive 1<unk> , autosomal recessive 3<unk> , autosomal recessive 4<unk> , autosomal recessive 5<unk> , autosomal recessive 6<unk> , autosomal recessive 21 - mutation in SCYL1 ORPHA:466794<unk> , autosomal recessive, with axonal neuropathy<unk> , X-linked, 2<unk> , X-linked, 3<unk> , X-linked, 4
Spinocerebellar ataxia
Paroniria
Truncal ataxia
Non-progressive congenital ataxia
Benign hereditary chorea
Dysthanasia
Spinal and bulbar muscular atrophy
Ataxic cerebral palsy