[A neonate with developmental retardation].

An 6-month-old boy was admitted to the hospital with hypotonia, hyperpnoeic and apnoeic episodes, and abnormal eye movements. Cranial MRI revealed prominent superior cerebellar peduncles with dysgenesis of the vermis and a deep interpeduncular fossa, resulting in the characteristic image of a 'molar tooth' malformation of the brainstem. This is a classical sign of Joubert syndrome.