Non-progressive congenital ataxias.

Congenital ataxias (CA) are rare, predominantly non-progressive syndromes characterized by marked hypotonia, developmental delay followed by the appearance of ataxia. Most children show marked speech and cognitive developmental problems. Non- progressive CA (NPCA) can be divided into pure CA without additional symptoms and syndromes with CA. Pure CA can be due to cerebellar malformations as (hereditary or non-hereditary) cerebellar hypoplasia, Dandy Walker syndrome, or occasionally supratentorial abnormalities. Ataxic syndromes are less frequent, but more distinctive. There are syndromes (e.g. Joubert syndrome) where ataxia is a cardinal feature and others where ataxia is only an occasional symptom. Acquired ataxias, due to congenital cytomegalovirus infection or perinatal problems, form a small third group. In about half of all cases with NPCA, aetiology and inheritance are still unknown. Diagnosis of NPCA is made by a typical history and careful clinical examination. Diagnosis of a more distinctive ataxic syndrome may be possible on clinical grounds. Neuroimaging with special attention to the posterior fossa will aid accurate clinical classification. Early progressive ataxias require careful differentiation from other types.