Fig. 1

a, Sagittal, b, Axial, and c, Coronal T2-weighted MR images of a 2-day-old term male newborn with Oral-Facial-Digital syndrome type VI (a phenotype of Joubert syndrome) show severe hypoplasia of the cerebellar vermis and both cerebellar hemispheres, the characteristic molar tooth sign including thickened and elongated superior cerebellar peduncles and a deepened interpeduncular fossa, and a hypothalamic hamartoma (arrows)(reprinted with permission from Poretti A et al., AJNR Am J Neuroradiol, 2008;29:1090–91). d, Sagittal, e, Axial, and f, Coronal T2-weighted MR images of a 5-day-old term male neonate with rhombencephalosynapsis reveal continuity of the cerebellar hemispheres, dentate nuclei, and superior cerebellar peduncles without a midline intervening vermis. On the sagittal image, no primary fissure is seen. In addition, dysplasia of the tectal plate, obstruction of the Sylvian aqueduct at the level of the inferior colliculi, and marked supratentorial hydrocephalus. Note that the dentate nucleus is visible on a midsagittal image, while in normal anatomy the vermis separates the dentate nuclei in the midline