Sagittal Perspective of Cerebellar Lobules, Fourth Ventricle, and Brainstem. The cerebellum is divided into 10 lobules. Lobules I-III are contained within the anterior lobe. Lobule X is more commonly referred to as the flocculonodular lobe. The remainder of the lobules span both the cerebellar vermis and the cerebellar hemisphere. The regional association between the middle cerebellar peduncle and the fourth ventricle is apparent in this image and highlights nicely the challenge in achieving fourth ventricular floor exposure from a Telovelar approach given the cerebellar hemispheres are pedicled closely to this region. The foramen of Luschka and lateral wall of the fourth ventricle are demonstrated. (Image courtesy of AL Rhoton, Jr.)