Table 1.

The spinocerebellar ataxias

SCA	Gene/locus	Mutation type	Key symptoms in addition to cerebellar ataxia	MRI characteristics (atrophy)
				Brainstem	Pons	Cerebellar hemispheres	Vermis	Basal ganglia	Cortical areas
1	ATXN1/6p22.3	CAG repeat	Dysphagia	++	++	++	++	++	+
2	ATXN2/12q24.12	CAG repeat	Oculomotor symptoms	++	+++	++	++	(+)	++
3	ATXN3/14q32.12	CAG repeat	Dystonia, parkinsonism, neuropathy	++	+	++	++	+
4	/16q21.1	Unknown	Sensory neuropathy			+	+
5	SPTBN2/11q13.2	Missense, n-frame deletion	Nystagmus	−	−	++	++	−	−
6	CACNA1A/19p13.2	CAG repeat		+	+	+++	+++	+	(+)
7	ATNX7/3p14.1	CAG repeat	Visual loss		+++	++	++		+
8	ATXN8OS/13q21	CTG repeat	Sensory neuropathy, spasticity	−	−	++	++		−
9	Unknown	Unknown	Ophthalmoplegia, pyramidal and extrapyramidal signs
10	ATXN10/22q13.31	ATTCT	Epilepsy	−		++	++
11	TTBK-2/15q15.2	Frameshift	Nystagmus			+	+
12	PPP2R2B/5q32	CAG repeat	Tremor	−	−	+	+	−	+
13	KCNC3/19q13.33	Point mutation	Mental retardation	+	+		+
14	PRKCG/19q13.42	Missense, deletion	Myoclonus		(+)	++	++	−	−
15/16	ITPR1/3p26.1	Missense, frameshift	Tremor	−	−	+	++
17	TBP/6q27	CAG repeat	Dementia, psychiatric disorders			+++	++	++	++
18	/7q22-32	Unknown	Sensory neuropathy, muscle atrophy			+	+		(+)
19/22	KCND3/1p21-q21	Unknown	Mental retardation			+	+		(+)
20a	/11q12	260 kb duplication	Dysphonia, myoclonus			++	++
21	/7p21.3-p15.1	Unknown	Mental retardation			+	+
23	PDYN/20p13	Missense mutation	Sensory neuropathy, pyramidal signs			+	+
24	/1p36	Unknown	Pyramidal signs, axonal polyneuropathy
25	/2p21-13	Unknown	Sensory neuropathy, gastrointestinal features	−	−	++	++
26	/19p13.3	Unknown		−	−	++	++
27	FGF14/13q33.1	Point mutation	Dyskinesia, metal retardation	−	−	++	++	−	−
28	AFG3L2/18p11.21	Missense mutation	Oculomotor symptoms	−	−	++	++		−
29	ITPR1/3p26	Missense mutation	Cognitive impairment
30	/4q34.3-q35.1	Unknown
31	TK2, BEAN/ 16q21	TGGAA repeat	Muscular hypotonia, auditory dysfunction
32	/7q32-q33	Unknown
34	/16p12.3-q16.2	Unknown	Cutaneous plaques
35	TGM6/20p13	Missense mutation	Oculomotor symptoms
36	NOP56/20q13	Repeat expansion	Mus spasticity, fasciculations, atrophy of tongue and skeletal muscles

AFG3L2 ATPase family gene 3 like 2, ATXN ataxin, BEAN brain expressed associated with NEDD-4, CACNA1A calcium channel voltage-dependent P/Q type alpha 1A subunit, FGF14 fibroblast growth factor 14, ITPR1 inositol triphosphate receptor type 1, KCNC3 potassium voltage-gated channel Shaw-related subfamily member 3, KCND3 potassium voltage-gated channel subfamily D member 3, NOP56 ribonucleoprotein, PDYN prodynorphin, PPP2R2B serine/threonine-protein phosphotase 2A, PRKCG protein kinase C gamma type, SPTBN2 beta-III-spectrin, TBP TATA-box binding protein, TK2 thymidine kinase 2, TGM6 transglutaminase 6, TTBK2 tau tubulin kinase 2, − no atrophy, (+) mild/inconsistently reported, + mild atrophy, ++ moderate atrophy, +++ severe atrophy, blank not reported/unknown

^aCalcifications of dentate nucleus