Cerebellar Hypoplasia (CH) has been described in the context of various clinical entities: chromosomal anomalies, in utero exposure to toxins and infectious agents, metabolic disorders and a wide variety of rare genetic neurological diseases. Cerebellar maldevelopment can involve the vermis and/or the cerebellar hemispheres from partial to total agenesis. It can be confined to the cerebellum (Norman type of granular cell hypoplasia, Dandy Walker malformation (see this term)), or affect other CNS structures: the midbrain (molar tooth syndromes MTS), pons and medulla (ponto-cerebellar hypoplasia PCH), cerebral cortex (lissencephaly cerebellar hypoplasia syndromes LCH (see this term)). The distinction between cerebellar hypoplasia and cerebellar atrophy is not always clear, as phenomena of secondary atrophy may occur in a hypoplastic cerebellum. A relevant number of rare cerebellar syndromes with CH and associated renal, ocular, hepatic or cardiac malformations have been described to date: Gillespie, Ritscher-Schinzel, Oro-facio-digital type II, Hoyeraal-Hreidarsson (see these terms). Inheritance can be autosomal recessive, autosomal dominant or X-linked. Gene mutations have been identified in LCH (reelin), PCH (PMM2), X-linked cerebellar hypoplasia (OPHN1, DCK1) and several loci have been mapped for autosomal recessive ataxias (see this term). Mutations of a pancreatic transcription factor (PTF1A) have been identified in a family with pancreatic and cerebellar agenesis. Heterozygous loss of ZIC1 and ZIC 4 genes has been involved in Dandy Walker Malformation. The clinical spectrum associated with cerebellar hypoplasia is variable, depending on the etiology. The most common findings are developmental and speech delay, hypotonia, ataxia and abnormal ocular movements. The clinical diagnosis must be confirmed by cerebellum and brain imaging with a long term follow-up, careful metabolic and developmental work-up. Mental status is an important element of prognosis. In most cases no specific treatment is available.
Last update: February 2005