The 'molar tooth sign' in Joubert syndrome.

The molar tooth sign is seen in very few conditions and is a very rare paediatric central nervous system congenital anomaly. Molar tooth sign is the result of cerebellar vermis hypoplasia, thick and maloriented superior cerebellar peduncles, and an abnormally deep interpeduncular fossa. In Joubert syndrome this is seen in about 85% of patients. We present a case of 13 months old baby boy with recurrent episodes of fits and hyperpnoea, regression of milestones and developmental delay. MRI examination showed the characteristic molar tooth sign with apposition of cerebellar hemispheres, batwing-shaped fourth ventricle communicating through a thin fissure with foramen of Magendie, cerebellar vermis agenesis and deep interpeduncular fossa consistent with diagnosis of Joubert syndrome.