What are the spinocerebellar ataxia (SCA) equivalents for olivopontocerebellar atrophy (OPCA)?

Updated: Dec 17, 2018
  • Author: Sombat Muengtaweepongsa, MD, MSc; Chief Editor: Selim R Benbadis, MD  more...
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Although Table 1 gives the SCA equivalent for the OPCAs, many neurology residents have asked to see a table showing how the OPCAs fit into the larger SCA category. Table 3 gives that framework and the OPCAs are identified in the larger context.

Table 1. Most Common OPCAs With Alternative Names (Open Table in a new window)


OPCA Names

Other Names

Genetic Pattern





Menzel type OPCA





Gene map locus 6p23 expanded (CAG)n trinucleotide repeat in the ataxin-1 gene (ATXN1; 601556); autosomal dominant; genetic test available

Onset 30-40 years; ataxia, spasticity, dysarthria, ophthalmoplegia, slow saccades, nystagmus, optic atrophy, pyramidal tract signs; rare extrapyramidal signs; some have dementia; neuropathy occurs late [19]




Gene map locus 12q24 expanded (CAG)n trinucleotide repeat in the gene encoding ataxin-2 (ATXN2; 601517); autosomal dominant; genetic test available

Onset in 30s; ataxia, dysarthria, muscle cramps; slow saccades; ophthalmoplegia; peripheral neuropathy; dementia (some); no pyramidal or extrapyramidal features [20]


OPCA-II, Fickler-Winkler type OPCA

Fickler-Winkler Syndrome

Gene/biochemistry not known; autosomal recessive

Adult-onset; cerebellar ataxia, albinism, impaired intellect; neurological impairments similar to OPCA-I but no involuntary movements or sensory loss [9, 21, 22]


OPCA-III, OPCA-3, OPCA with retinal degeneration

ADCA-II, SCA-7, OPCA with macular degeneration and external ophthalmoplegia

Gene locus 3p21.1-p12; expanded trinucleotide repeat in the gene encoding ataxin-7 (ATXN7; 607640); autosomal dominant; genetic test available

Onset in mid 20s; initially pigmentary retinal degeneration then ataxia, dysarthria, ophthalmoplegia, slow saccades, pyramidal tract signs [20]

^ 164600 Number now obsolete; considered the same as # 164400 (see first row above)

OPCA-IV, Schut-Haymaker type OPCA


Genetics unclear; glutamate dehydrogenase deficiency suspected in some; some cases may be linked to OPCA locus at chromosome 6p; may not be a pure genetic type; now thought to be same as OPCA-I (SCA-1)

Adult-onset ataxia with involvement of cranial nerves IX, X, and XII [23]


OPCA-V, OPCA-5, OPCA with dementia and extrapyramidal signs

This may be the same as SCA-17

Autosomal dominant; genetic test available for SCA-17, but unclear if this is the same

Cerebellar ataxia, rigidity, dementia; neuronal loss in cerebellum, basal ganglia, substantia nigra, olivary nuclei, cerebral cortex [24, 8]


OPCA-X, OPCA X-linked-1

SCA-X1 (do not confuse this with SAX-1, the locus for hereditary (autosomal dominant) spastic ataxia [%108600])

X-linked, some cases linked to Xp11.21-q21.3; not homogenous; gene(s) not known

Onset in first or second decade and often bedbound by 20s; loss of cerebellar Purkinje cells, inferior olivary cells, myelin loss in spinocerebellar tracts, posterior columns, and corticospinal tracts; gait and limb ataxia, intention tremor, dysmetria, dysdiadochokinesia, dysarthria, and nystagmus; some have peripheral neuropathy [25, 26]

Table 3. Dominant SCAs with OPCAs Identified (Open Table in a new window)

Disease OMIM #

Disease Names


GeneProduct (OMIM #)





ATXN1, 6p23

CAG expansion repeat in N-terminal coding region of Ataxin-1 (*601556);

Onset 30-40 years; ataxia, spasticity, dysarthria, ophthalmoplegia, slow saccades, nystagmus, optic atrophy, pyramidal tract signs; rare extrapyramidal; signs; some have dementia; neuropathy occurs late. Expansion repeat causes toxic gain of function via abnormally long ataxin-1. This worsens in subsequent generations.

Menzel, 1891 [37] ; Waggoner et al, 1938 [38] ; Schut, 1950 [39] ; Schut and Haymaker, 1951 [23] ; Orr et al, 1993 [40]

Donato et al. 2012 [41]



ATXN2, 12q24

Ataxin-2 (601517); genetic test available

Onset in 30s; ataxia, dysarthria, muscle cramps; slow saccades/ophthalmoplegia; peripheral neuropathy, hyporeflexia, dementia in some; no pyramidal or extrapyramidal features

Boller and Segarra, 1969 [42] ; Wadia and Swami, 1971 [43] ; Ueyama et al, 1998 [44]


SCA-3 or Machado-Joseph disease, ADCA-1

ATXN3, 14q24.3-q31

Machado-Joseph disease protein 1(ATXN3). (607047); genetic test available

All have ataxia, dysarthria, ophthalmoplegia; type I onset in mid 20s with facial-lingual myokymia, pyramidal and extrapyramidal features; type II onset in 40s; type III onset in mid 40s with peripheral neuropathy (weakness and atrophy)

Nakano et al, 1972 [45] ; Kawaguchi et al, 1994 [46]



Gene unknown, 16q22.1 (same region as #117210 below)


Onset average approximately 40 years (range, 19-72 y); pure ataxia in some cases, most have sensory axonal neuropathy; deafness in some

Gardner et al, 1994 [47] ; Hellenbroich et al, 2003 [48]


SCA, 16q22-linked ADCA-3

PLEKHG4, 16q22.1

Puratrophin-1 (609526)

Typically pure cerebellar ataxia with gait ataxia, cerebellar dysarthria, limb ataxia, decreased muscle tone, horizontal-gaze nystagmus; lacks other feature seen in SCA-4, ADCA-1 (but sometimes called SCA-4)

Ishikawa et al, 2005 [49]



SPTBN2, 11p13

Spectrin beta chain, brain 2 (604985)

Onset mid 30s; downbeat nystagmus; ataxia, dysarthria, impaired smooth pursuit, and gaze-evoked nystagmus; slow progression; both vermal and hemispheric cerebellar atrophy, normal life expectancy

Ikeda et al, 2006 [50]



CACNA1A, 19p13

Voltage-dependent P/Q-type Ca+2 channel alpha-1a subunit (601011); genetic test available

Onset 20-40 years; ataxia, dysarthria, nystagmus, distal sensory loss, normal life expectancy

Subramony et al, 1996 [51] ; Zhuchenko et al, 1997 [52]



ATXN7, 3p21.1-p12

Ataxin-7 (607640); genetic test available

Onset mid 20s; pigmentary retinal degeneration, ataxia, dysarthria, ophthalmoplegia, slow saccades, pyramidal tract signs

David et al, 1997 [53] ; Harding, 1982 [7]



KLHL1AS, 13q21

Genetic test available

Onset 20s to 70s; ataxia, dysarthria, nystagmus, impaired smooth pursuit

Koob et al, 1999 [54] ; Ikeda et al, 2000 [55] ; Factor et al, 2005 [56] (Factor et al case was actually consistent with MSA)



Unassigned category


Unassigned category

Unassigned category



ATXN10, 22q13

Ataxin-10; genetic test available

Onset in 20s; ataxia, dysarthria, nystagmus, epileptic seizures; to date only found in Mexican families

Grewal et al, 1998 [57] ; Zu et al, 1999 [58] ; Grewal et al, 2002 [59]



SCA11, 15q14-q21.3

Tau-tubulin kinase 2

Onset at 20-40 years; ataxia, dysarthria, nystagmus

Worth et al, 1999 [60]



PPP2R2B, 5q31-q33

Serine/threonine protein phosphatase 2A, 55-kd regulatory subunit B, beta isoform; genetic test available

Onset at 8-55 years, commonly 30s; upper extremity and head tremor, gait ataxia, ophthalmoplegia, hyperreflexia, bradykinesia, dementia

Holmes et al, 1999 [61] ; Fujigasaki et al, 2001 [62]



KCNC3, 19q13.3-q13.4

Voltage-gated K+ channel, subfamily C member 3

Onset in childhood; ataxia, dysarthria, mental retardation; slow progression

Waters et al, 2006 [63]



PRKCG, 19q13.4

Kinase C, gamma type; genetic test available

Onset mostly in most those older than 39 years; ataxia, dysarthria, nystagmus; younger patients (< 27 y) also had intermittent axial myoclonus prior to ataxia

Yamashita et al 2000 [64] ; Brkanac, Bylenok et al 2002 [65] ; Chen, Brkanac et al 2003 [66] ; Yabe et al 2003 [67]



Gene unknown, 3p26.1-p25.3

Inositol 1,4,5-triphosphate receptor type 1

Similar to SCA-6 and SCA-8; MRI-proven cerebellar atrophy; onset at 10-50 years; slowly progressive pure cerebellar ataxia, ataxic dysarthria, tremor; may have head titubation, nystagmus, oculovestibular reflex abnormalities, mild hyperreflexia (no spasticity or Babinski signs)

Storey et al, 2001 [68] ; Knight et al, 2003 [69] ; Hara et al, 2004 [70]



SCA16, 8q22.1-q24.1


MRI-proven cerebellar atrophy without brainstem involvement; onset at 20-66 years; pure cerebellar ataxia, some with head tremor, slow progression

Miyoshi et al, 2001 [71]


SCA-17, may be OPCA-5

TBP, 6q27

TATA-box–binding protein; genetic test available

Onset at 3-55 years; ataxia and involvement of pyramidal, extrapyramidal, and, possibly autonomic system; intellectual impairment, dementia, psychosis, chorea; presentation similar to Huntington disease; degeneration of caudate, putamen, thalamus, frontal cortex, temporal cortex, and cerebellum

Nakamura et al, 2001 [72] ; Rolfs et al, 2003 [73] ; Maltecca et al, 2003 [74]



SCA18 7q22-q32


Onset in teens, 20s, and 30s; sensorimotor neuropathy with ataxia; gait abnormality, dysmetria, hyporeflexia, muscle weakness and atrophy, axonal neuropathy, decreased vibratory and proprioceptive sense

Brkanac et al, 2002 [75]





Onset at 12-40 years; gait and limb ataxia, hyporeflexia, dysphagia, dysarthria, and gaze-evoked horizontal nystagmus; cerebellar atrophy on MRIs

Schelhaas et al, 2001 [76] ; Verbeek et al, 2002 [77] ; Chung et al, 2003 [78] ; Schelhaas et al, 2004 [79]



SCA20, 11p13-q11


Onset at 19-64 years; dysarthria, gait ataxia, upper limb, slow progression; more variable features are mild pyramidal signs, hypermetric saccades, nystagmus, palatal tremor, slow cognitive decline; CT scan shows dentate calcification

Knight et al, 2004 [80]



SCA21, 7p21-15


Onset at 6-30 years; cerebellar ataxia, limb ataxia and akinesia, dysarthria, dysgraphia, hyporeflexia, postural tremor, resting tremor, rigidity, cognitive impairment, cerebellar atrophy

Devos et al, 2001 [81] ; Vuillaume et al, 2002 [82]





Now believed to be identical to SCA-19 (Schelhaas et al, 2004 [79] ) though Chung et al (2004) [78] dispute this

Schelhaas et al, 2001 [76] ; Verbeek et al, 2002 [77] ; Chung et al, 2004 [78] ; Schelhaas et al, 2004 [79]





Onset at 40s and 50s; slow progression; gait and limb ataxia, dysarthria (varies), slow saccades and ocular dysmetria, decreased vibratory sense; severe cerebellar atrophy

Verbeek, et al, 2004 [83]



SCA25, 2p21-p13


Onset in childhood; invariable features are cerebellar ataxia; variable features are lower limb areflexia, peripheral sensory neuropathy, nystagmus, decreased visual acuity, facial tics, extensor plantar responses, urinary urgency, and gastrointestinal symptoms

Stevanin et al, 2004 [84]





Onset t 25-60 years; pure cerebellar signs, including ataxia of the trunk and limbs, dysarthria, and irregular visual pursuit movements; intelligence normal; MRI shows atrophy of cerebellum, sparing pons and medulla

Yu et al, 2005 [85]



FGF14, 13q34

Fibroblast growth factor 14 (601515)

Onset in childhood; cerebellar ataxia, tremor, low IQ, aggressive behavior, eye movement abnormalities are nystagmus, cerebellar dysarthria, head tremor, orofacial dyskinesias, cerebellar atrophy, pes cavus, axonal sensory neuropathy, neuronal loss in cerebral cortex, amygdala, and basal ganglia

van Swieten et al, 2003 [86]




AFG3-like protein 2

Onset at 19.5 years (range, 12-36 y); imbalance and mild gait incoordination; gaze-evoked nystagmus, slow saccades, ophthalmoparesis, and, often, ptosis; frequently lower limb hyporeflexia

Cagnoli et al, 2006 [87]


Dentatorubral-pallidoluysian atrophy (DRPLA)

DRPLA, 12p13.31

Atropin-1–related protein (607462); genetic test available

Onset in 20s to 30s; myoclonic epilepsy, dementia, ataxia, choreoathetosis, degeneration of dentatorubral and pallidoluysian systems

Naito and Oyanagi, 1982 [88] ; Koide et al, 1994 [89]


Episodic ataxia type 1, EA-1

KCNA1, 12p13

K+1 voltage-gated channel (A1) (600111); genetic test available on research basis

Onset usually in childhood; continuous muscle movement (myokymia) and periodic ataxia

Van Dyke et al, 1975 [90] ; Hanson et al, 1977 [91] ; Gancher and Nutt, 1986 [92] ; Browne et al, 1994 [93] ; Brandt and Strupp, 1997 [94] ; Eunson et al, 2000 [95]


Episodic ataxia type 2, EA-2

CACNA 1A, 19p13

Voltage-dependent P/Q-type Ca+2 channel alpha-1A subunit (601011); genetic test available on research basis

Onset in childhood; ataxia, downbeating nystagmus dizziness treated with acetazolamide; no progression after childhood; cerebellar atrophy

Parker, 1946 [96] ; White, 1969 [97] ; Subramony et al, 2003 [98] ; Spacey et al, 2005 [99] ; Imbrici et al, 2005 [100]


Episodic ataxia type 3, EA-3



Onset at 1-42 years; vestibular ataxia, vertigo, tinnitus, interictal myokymia

Steckley et al, 2001 [101] ; Cader et al, 2005 [102]


Episodic ataxia type 4, EA-4



Onset in third to sixth decade; recurrent attacks of vertigo, diplopia, and ataxia; slowly progressive cerebellar ataxia in some; periodic vestibulocerebellar ataxia in an autosomal dominant pedigree pattern, defective smooth pursuit, gaze-evoked nystagmus, ataxia, vertigo

Farmer and Mustian, 1963 [103] ; Vance et al, 1984 [104] ; Damji et al, 1996 [105]


Episodic ataxia type 5, EA-5

CACNB 4, 2q22-q23

Voltage-dependent L-type calcium beta-4 subunit (+601949)

Onset in third or fourth decade; mutation at C104F in French-Canadian family; ataxia similar to EA-2; severe episodic lasting hours to weeks; treatment with acetazolamide; interictal ataxia includes gait and truncal, mild dysarthria; nystagmus (downbeat, spontaneous, gaze evoked); seizures

Escayg et al, 1998 [106] ; Escayg et al, 2000 [107] ; Herrmann et al, 2005 [108]


Choreoathetosis spasticity, episodic, CSE

12p13 (close to potassium channel gene KCNA1 but not the same)


Onset at 2-15 years; paroxysmal choreoathetosis with episodic ataxia and spasticity

Auburger et al, 1996 [109] ; Müller et al, 1998 [110]


Hereditary (autosomal dominant) spastic ataxia

SAX1, 12p13


Onset at 10-20 years; lower limb spasticity, generalized ataxia with dysarthria, dysphagia, impaired ocular movements, gait abnormalities; brain and cord MRIs normal; neuropathology shows midbrain neuronal loss

Ferguson and Critchley, 1929 [111] ; Gayle and Williams, 1933 [112] ; Mahloudji, 1963 [113] ; Meijer et al, 2002 [114] ; Grewal et al, 2004 [115]

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