Teaching Case

Psychomotor retardation. Dystonia, ataxia. Respiratory disturbance. Abnormal eye movements.

Presented with marked psychomotor retardation. Dystonia, ataxia, and vertical nystagmus were evident. It was noted that she had episodes of hyperpnea and apnea, and abnormal eye movements during the neonatal period. On an MR imaging examination at 1.5 Tesla, FLAIR (fluid attenuated inversion recovery), turbo spin-echo T2-weighted, and turbo inversion recovery T1-weighted images were obtained. An anisotropic diffusion imaging sequence, PSIF (reverse fisp=fast imaging in steady state precession) was added to the imaging protocol.

Joubert's syndrome is a rare condition representing one of the developmental defects of the cerebellar vermis. The principal clinical signs of Joubert's syndrome include respiratory disturbances, and abnormal eye movements during the neonatal period, and mental retardation as the child ages. The prognosis is usually poor. Associated findings may include unsegmented midbrain tectum, occipital meningoencephalocele, callosal dysgenesis, chorioretinal coloboma, sacral dermal sinus, polydactyly, and cystic kidney disease. The most consistent radiological change of the syndrome is dysgenesis of the vermis, which results in a "bat-wing" and "triangular" shaped fourth ventricle, and a prominent appearance of the superior cerebellar peduncles. In Joubert's syndrome, there is a characteristic vermian cleft, although recently a number of cases with vermian clefts unassociated with the clinical findings of the syndrome have been reported. From radiological point of view, Joubert's syndrome is anatomically opposite of rhombencephalosynapsis in which there is fusion of cerebellar hemispheres through the dentate nuclei, and associated vermian dysgenesis. Meanwhile, it may be noteworthy to mention that the only supratentorial condition associated with fusion of the cerebral hemispheres and thalami, is holoprosencephaly. On the other hand, the entities associated with cerebral clefts include schizencephaly, and porencephaly.