Midbrain disconnection: an aetiology of severe central neonatal hypotonia.

A full term girl exhibited massive hypotonia related to severe posterior fossa abnormalities consisting of pontocerebellar hypoplasia with midbrain disconnection. The latter was due to lack of one and marked hypoplasia of the other cerebral peduncles. In addition, there was mild vermian and cerebellar hypoplasia. Compared to usual pontocerebellar hypoplasia, the midbrain disconnection is a distinctive feature of our case. It is a rare malformation only three similar cases have previously been described.