Central nervous system disorders

II/1.3: The brain’s medial surface

Along with medially facing gyri and sulci, in wider medical sense, the 3rd ventricle and the commissural pathways which appear when we cut the brain into half, also belong here, however, we are not going to describe them here.

On the medial surface of the frontal lobe is the superior frontal gyrus, behind it is the turn of the precentral gyrus, and most inferiorly is the straight gyrus. The area under the genu of the corpus callosum is called subcallosal area, while the convolution part in front of the terminal lamina is called paraterminal gyrus.

The fissure of Rolando and the paracentral lobule which lays behind it in the continuation of the postcentral gyrus, turn onto the medial surface of the parietal lobe. The precuneus is seen behind itand it is bordered by the upward bending marginal branch of the cingulate sulcus from the front and the subparietal sulcus from below.

Its posterior border is the parietooccipital sulcus, and behind it is the wedge-shaped cuneus which is separated from the lingual gyrus by the calcarine sulcus.

In a functional point of view, the precentral and postcentral gyri need to be emphasized, because their medial superficial parts represent the distal parts of the lower limb according to Penfield and Rasmussen’s homonculus. The calcarine sulcus and the surrounding cortical parts correspond to the primary, secondary and tertiary visual areas (Br.17, 18, 19). The primary area is called striate area, the secondary is the parastriate, and the tertiary is the peristriate area.