Joubert syndrome

  • total aplasia of cerebellar vermis
  • failure of formation of decussation of superior cerebellar peduncles
  • lack of pyramidal decussations
  • other anomalies of midbrain crossing tracts and their nuclei
  • associated anomalies: renal cysts, ocular abnormalities, liver fibrosis, hypothalamic hamartomas, polymicrogyria
clinical presentation
  • tachypnea
  • abnormal eye movements
  • ataxia
  • occasionally clinically normal
  • cleft within vermis
  • small midbrain
  • superior peduncles enlarged
  • molar tooth appearance: seen on axial images, due to lack of superior cerebellar decussation
  • batwing appearance: due to enlarged 4th ventricle with cerebellar hypoplasia, midline vermian cleft and dysplastic small vermis