Our work thus clarifies the etiology of the cerebral phenotype associated to CRB2 variants, revealing that unlike Sylvius Aqueduct stenosis where the third ventricle is usually enlarged, in CRB2 mutated cases, only the lateral ventricles are dilated, the downstream tract being atretic from the third ventricle to the medulla. Here, CRB2 is linked to Aqueductal stenosis.