Imaging Findings In Joubert Syndrome

Joubert syndrome is a rare autosomal recessive disorder characterized by abnormal respiratory pattern and eye movements, hypotonia, ataxia, developmental retardation with neuropathologic abnormalities of cerebellum and brainstem including inherited hypoplasia or aplasia of vermis. The reported prevalence is less than 1 in 100,000. Cross-sectional axial imaging demonstrates isolated abnormality of the cerebellum, consisting of: • small dysplastic or aplastic cerebellar vermis • absence of fibre decussation in the superior cerebellar peduncles and pyramidal tracts , which can be assessed by diffusion tensor imaging • abnormal inferior olivary nucleus • dysplasia and heterotopia of cerebellar nuclei The posterior fossa typically shows a bat wing 4th ventricle and prominent thickened elongated superior cerebellar peduncles giving characteristic molar tooth sign like appearance. In a minority of cases minor lateral ventriculomegaly (6 - 20% of cases), and corpuscallosal dysgenesis (6-10% of cases) is also present.