The Anatomy of the Posterior Cranial Fossa

Abstract

The posterior cranial fossa contains the most complex intracranial anatomy. Posterior fossa is strategically important situated at the outlet of the cerebrospinal fluid flow from the ventricular system. The posterior fossa extends from the tentorial incisura, through which it communicates with the supratentorial space, to the foramen magnum, through which it communicates with the spinal canal. It is bounded in front by dorsum sellae, the posterior part of sphenoid body, and clival part of the occipital bone; behind by the lower portion of the squamosal port of the occipital bone; and on each side by the petrous and mastoid parts of the temporal bone, the lateral part of occipital bone, and above and behind by a small part of mastoid angle of the parietal bone. The cerebellum consists of three anatomical parts; a median vermis and two lateral hemispheres. The central vermis is elevated above the level of the hemispheres on the upper surface of the cerebellum, contrary to its deep depression on the suboccipital surface. The cerebellum has fissures that divide the organ into series of layers or leaves. The largest and deepest fissure is the horizontal sulcus. The horizontal sulcus divides the semilunar lobule into inferior and superior semilunar lobules. The vermis is positioned between the two hemispheres and is an important structure in the transvermian approach as it connects both hemispheres. Culmen represents the most apical part of the vermis at the tentorial surface. From posterior to anterior, the subdivisions of superior vermis are represented by lingula, central lobule, monticulus, and folium vermis. Vermal parts of the posterior lobe are, in the following order, the declive, folium, tuber, pyramid, and uvula. The folium vermis is a short, narrow, and concealed band-like structure at the posterior extremity of the vermis. The superior semilunar lobule occupies the posterior third of the upper surface of the hemisphere and connected below by the horizontal sulcus. The superior semilunar lobule receives fibers mainly from middle cerebellar peduncles that are referred to as pontinecerebellar and corticocerebellar fibers.