Genetic aspects of congenital cerebellar ataxia

Congenital cerebellar ataxia comprises a heterogeneous group of birth defects involving brain stem and cerebellum, characterised by ataxia, spasticity, choreoathetoid movements and mental retardation. Three children with congenital cerebellar malformations are described. The presenting features were benign enlargement of head, myoclonic jerks, episodes of hypernoia, nystagmus, ataxia, motor delay and mental retardation. Computerised tomography revealed Dandy-Walker cyst in one case and in two cases cerebellar vermis agenesis was associated with a variable degree of brain stem involvement. Retinal dysplasia and post-axial polydactyly were associated abnormalities in one case as reported in Joubert's syndrome, an autosomal recessive type of familial cerebellar vermis dysgenesis. Genetic factors in the pathogenesis of congenital cerebellar ataxia are reviewed. The relevance of computerised tomography, electroretinography and prenatal diagnosis by fetal ultrasound is discussed. Genetic counselling in congenital cerebellar ataxia presenting in the first year of life is important because of the high risk of recurrence.