Bat wing 4th ventricle

Bat wing 4^th ventricle sign refers to the morphology of the fourth ventricle in the Joubert anomaly and related syndromes. The absence of a vermis with apposed cerebellar hemispheres gives the fourth ventricle an appearance reminiscent of a bat with its wings outstretched.

It is best demonstrated on an axial imaging plane and could be easily missed on sagittal and coronal images ³.