Rare diseases · Sign or symptom
Cerebellar hypoplasia
Small cerebellum
HP:0001321
What it means
Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time.
By prenatal ultrasound, cerebellar hypoplasia is diagnosed if the cerebellum measures more than two standard deviations below the mean. In adults, cerebellar hypoplasia is typically diagnosed by computer tomography or magnetic resonance imaging. Cerebellar hypoplasia can be diagnosed if there is a small cerebellum with fissures of normal size compared with the folia (this is a distinguishing characteristic compared with cerebellar atrophy). Cerebellar hypoplasia (CH) refers to an underdevelopment of the cerebellum. This category of cerebellar malformation is distinct from Dandy Walker malformation in that it does not involve a concurrent enlargement of the posterior fossa, and almost all individuals exhibit cognitive and motor impairments.
Rare diseases that can present with this103
Very common80–99%
20- 6q terminal deletion syndrome
- Autosomal recessive spastic ataxia with leukoencephalopathy
- Cerebellar-facial-dental syndrome
- Cerebellar hypoplasia-tapetoretinal degeneration syndrome
- Craniosynostosis-Dandy-Walker malformation-hydrocephalus syndrome
- Deafness-genital anomalies-metacarpal and metatarsal synostosis syndrome
- Hoyeraal-Hreidarsson syndrome
- Intellectual disability-obesity-brain malformations-facial dysmorphism syndrome
- Jung syndrome
- Lissencephaly type 3-metacarpal bone dysplasia syndrome
- Marinesco-Sjögren syndrome
- Microlissencephaly-micromelia syndrome
- Oculocerebrocutaneous syndrome
- Permanent neonatal diabetes mellitus-pancreatic and cerebellar agenesis syndrome
- Pontocerebellar hypoplasia type 2
- Port-wine nevi-mega cisterna magna-hydrocephalus syndrome
- Tetrasomy 5p syndrome
- Walker-Warburg syndrome
- X-linked intellectual disability-cerebellar hypoplasia syndrome
- X-linked intellectual disability, Najm type
Common30–79%
35- 7q11.23microduplication syndrome
- Alpha-N-acetylgalactosaminidase deficiency
- Autosomal recessive cutis laxa type 2, classic type
- Autosomal recessive spastic paraplegia type 66
- Brain malformation-congenital heart disease-postaxial polydactyly syndrome
- Cerebellar ataxia, Cayman type
- Cobblestone lissencephaly without muscular or ocular involvement
- Combined oxidative phosphorylation defect type 39
- Congenital muscular dystrophy with cerebellar involvement
- Congenital muscular dystrophy with intellectual disability and severe epilepsy
- Cortical dysgenesis with pontocerebellar hypoplasia due to TUBB3 mutation
- Craniotelencephalic dysplasia
- Crouzon syndrome
- Early-onset epilepsy-intellectual disability-brain anomalies syndrome
- Early-onset progressive leukoencephalopathy-central nervous system calcification-deafness-visual impairment syndrome
- Early-onset spastic ataxia-myoclonic epilepsy-neuropathy syndrome
- Isolated Dandy-Walker malformation
- Joubert syndrome with Jeune asphyxiating thoracic dystrophy
- Microcephaly-polymicrogyria-corpus callosum agenesis syndrome
- Mitochondrial myopathy-cerebellar ataxia-pigmentary retinopathy syndrome
- Mosaic trisomy 17 syndrome
- Neu-Laxova syndrome
- Neurodevelopmental delay-seizures-ophthalmic anomalies-osteopenia-cerebellar atrophy syndrome
- Non-progressive cerebellar ataxia with intellectual disability
- Otopalatodigital syndrome type 2
- PMM2-CDG
- Revesz syndrome
- S-adenosylhomocysteine hydrolase deficiency
- Spondylometaphyseal dysplasia, Sedaghatian type
- Tremor-ataxia-central hypomyelination syndrome
- Vici syndrome
- X-linked complicated corpus callosum dysgenesis
- X-linked intellectual disability-cerebellar hypoplasia-spondylo-epiphyseal dysplasia syndrome
- X-linked non progressive cerebellar ataxia
- Xq25microduplication syndrome
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions, and Orphanet separately records 1 disease where this sign is specifically absent. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Congenital cerebellar hypoplasia · Hypoplasia of cerebellum · Hypoplastic cerebellum · Underdeveloped cerebellum
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.