Brain malformations

Q.All are true regarding  brain malformations except

a. The posterior fossa is of normal size in cerebellar hypoplasia

b. Torcular–lambdoid inversion on MRI is seen in Dandy –Walker

syndrome

c.  ‘batwing appearance’ of the fourth ventricle  is seen in Joubert's

 syndrome

d.The ‘Molar   tooth’ appearance is noted  in

rhombencephalosynapsis

 

e. a nonenhancing mass with diffusely enlarged cerebellar folia is 

feature of  L'Hermitte-Duclos
ANS.---d

Joubert's syndrome  is  considered  as generalized developmental disorder of the midbrain and hindbrain. The imaging findings reflect a failure of formation of the decussation of the superior cerebellar peduncles, lack of the pyramidal decussations and other anomalies of the midbrain crossing tracts and their nuclei. On cross-sectional imaging the fourth ventricle is enlarged with a ‘batwing appearance’ and there is a cleft in the vermis. The midbrain is small. The ‘molar tooth’ appearance seen on axial images arises from the lack of the superior cerebellar decussation and the superior peduncles also appear enlarged.