On-line Table 1: Degenerative pattern Disease Posterior Fossa MRI Finding Additional MRI Findings Confirmatory Test Friedrich ataxia Normal, mild cord atrophy CA (mild), T2 cord SC, iron Genetic testing deposition at DN AOA CA (Ͻvermis) Reduced NAA and elevated mIns Clinical and lab findings (albumin, cholesterol, on MRS ␣-fetoprotein)g Ataxia-telangiectasia CA (Ͻvermis) WM and BG lesions, spinal cord Clinical, lab findings (␣-fetoprotein), and atrophy molecular genetic testing Infantile-onset CA Brain stem and cord atrophy, Clinical and genetic testing spinocerebellar ataxia cerebellum SC X-linked congenital CA Variable Genetic testing ataxiaa Mitochondrial disordersb CA WM, BG, and cortex SC; restricted Clinical, neuroimaging, and genetic testing DWI; lactate on MRS Ataxia with vitamin E Normal or mild CA Posterior and lateral columns of Clinical, lab findings (vitamin E, lipoprotein, deficiency the cord SC and acanthocytosis)h Dentatorubral- CA and midbrain atrophy Cerebral WM and brain stem SC, Genetic testing pallidoluysian atrophy brain atrophy Cerebrotendinous CA and SC in the DN WM, CST, BG, and brain stem SC; Clinical and lab findings (cholestanol in xanthomatosis brain atrophy serum and tendons) Episodic ataxia (types I CA (Ͻvermis) None Clinical, neuroimaging, and genetic analysis to VII) Infantile refsum disease SC in the dentate nucleus Brain atrophy; WM, CC, CST, and Clinical and lab findings (phytanic and brain stem SC pristanic acid) Infantile neuroaxonal SC and atrophy in the cerebellar Brain, WM, and optic nerve Clinical, neuroimaging, and genetic testing dystrophy cortex atrophy; Low T2 signal at GP Adrenomyeloneuropathy SC in the cerebellar WM and CST Brain involvement is less common Clinical and lab findings (very long-chain fatty than classic ADL acids) Aminoacidurias and CA in some subtypes Variable Clinical, neuroimaging, and genetic testing organic aciduriasc HABC CA (Ͻvermis) Diffuse hypomyelinization; BG, Clinical and neuroimaging CST, and WM atrophy and SC Gangliosidosis GM2d CA (Ͼvermis) Reduced NAA at MRS in Clinical and lab findings (␤-hexosaminidase) cerebellum and WM Neuronal ceroid CA Brain atrophy, low T2 signal in the Clinical, genetic, and lab testing lipofuscinosese thalamus, lactate on MRS (lipopigments from the skin) AR ataxia of Charlevoix- CA (Ͻsuperior vermis), T2 pons SC Small CST and large Clinical and genetic testing Saguenay pontocerebellar fibers at DTI Marinesco-Sjögren CA (or hypoplasia) Agenesis CC, small pituitary gland, Clinical and genetic testing syndrome cortex SC 4H syndrome CA and WM lesions Cerebral hypomyelinization, thin Clinical findings CC Alexander diseasee SC brain stem with enhancement Frontal subcortical WM and BG SC Clinical, lab findings (glial fibrillary acidic protein 5), and genetic testing HCC SC cerebellar WM, pons hypoplastic Diffuse WM hypomyelinization at Genetic testing the periventricular WM PPCARP SC dorsal cord None Clinical, neuroimaging, and genetic testing Wilson diseasef SC dorsal midbrain, CP and SCP Signs of hepatic failure; BG, Clinical, neuroimaging, and lab testing thalamus, and WM SC (copper/ceruloplasmin) Note:—AOA indicates ataxia with oculomotor apraxia (types 1 and 2); ADL, adrenoleukodystrophy; CA, cerebellar atrophy; CC, corpus callosum; CP, cerebral peduncle; CST, corticospinal tract; DN, dentate nucleus; GP, globus pallidus; mIns, myo-inositol; HABC, hypomyelination with atrophy of the basal ganglia and cerebellum; GM2 ϭ ganglioside 2; HCC, hypomyelination with congenital cataracts; SCP, superior cerebellar peduncle; PPCARP, posterior column ataxia and retinitis pigmentosa; SC, T2 high signal changes; BG, basal ganglia. a Including X-linked sideroblastic anemia and ataxia. b Including coenzyme q10 and POLG mutations. c Ataxia can occur in some diseases, including urea cycle disorders and mevalonic aciduria. d Late-onset. e Infantile-onset. f Ataxic-onset in children. g Reduced albumin, elevated cholesterol and ␣-fetoprotein in the plasma. h Acanthocytosis in abetalipoproteinemia.

AJNR Am J Neuroradiol ͉͉www.ajnr.org 1 On-line Table 2: Malformative pattern Disease Posterior Fossa MRI Finding Additional Imaging Findings Confirmatory Test Joubert syndrome and Molar tooth malformation Abnormal foliation and fissuration of Clinical and neuroimaging related diseases CH, CC dysgenesis, migration disorders, ventriculomegaly PCHa PC hypoplasia, “dragon-fly” configuration Microcephaly, abnormal CC, Clinical, neuroimaging, and (ϾPCH I or II) polymicrogyria genetic testing Rhomboencephalossinapsis Agenesis of the CV, fusion of the CH CC dysgenesis, ventriculomegaly Clinical and neuroimaging and DN Congenital disorders of PC hypoplasia with atrophy Brain stem hypoplasia, WM Clinical, neuroimaging, lab, and glycosylation superimposed (ϾCV) hypoplasia or atrophy genetic testing X-linked nonprogressive PC hypoplasia with atrophy Not described Clinical, neuroimaging, and congenital ataxiab superimposed genetic testing Vermian and Abnormal folia orientation and cortical Variable according to the genetic Neuroimaging hemispheric dysplasia mutation (cerebral malformation, cerebellar dysplasia brain atrophy, and ventriculomegaly can occur) VLDLR-associated Vermis and CH hypoplasia (Ͼinferior Mild cortical gyral simplification Clinical, neuroimaging, and cerebellar hypoplasiac portion of the vermis) genetic testing Dandy-Walker Enlarged PF, agenesis vermis, and Hydrocephalus, CC anomalies, PMG, Neuroimaging malformation elevated torcula heterotopia, cephalocele Pontine tegmental cap Cap tegmental appearance Dysgenesis of the corpus callosum, Neuroimaging dysplasia small inner auditory canal and/or VII/VIII nerves, abnormal tegmentum transverse fibers (DTI) Cortex malformation Cerebellar hypoplasia Cerebellar cyst, brain stem Clinical, neuroimaging, and disordersd hypoplasia, and WM lesions; genetic testing cobblestone lissencephaly and hydrocephalus, usually with more severe types of CMD Brain stem malformation Short pons, short midbrain/long pons or Variable and includes narrow Clinical and neuroimaging. with abnormal thick medulla isthmus, brain stem clefts, large segmentation pattern CH, absent CC, ventriculomegaly Unertan syndrome Cerebellar hypoplasia (Ͼvermis) Not described Clinical and neuroimaging. Höyeraal-Hreidarsson Cerebellar hypoplasia Small pons, thin CC, Clinical, neuroimaging, and syndrome hypomyelinization, bone lesion genetic testing Revesz syndrome Cerebellar hypoplasia Multiple cerebral calcifications, Clinical, neuroimaging, and leukodystrophy genetic testing Note:—PCH indicates pontocerebellar hypoplasia; PF, posterior fossa; CMD, congenital muscular dystrophy; CC, corpus callosum; CH, cerebellar hemispheres; CV, cerebellar vermis; DN, dentate nucleus; PC, pontocerebellar; PMG, polymicrogyria; VLDLR, very low density lipoprotein receptor. a Types I-VII. b Including isolated and X-linked subtypes. c Dysequilibrium syndrome. d Four most common CMD groups (mild phenotype).

2 ͉ AJNR ͉͉www.ajnr.org