Surgical Anatomy of Supratentorial Midline Lesions

diameter of the pericallosal artery at its origin was similar on both the right (average, 2.6 mm) and left (average, 2.5 mm) sides. The A2 segment
of the pericallosal artery coursed in the subcallosal area, generally in an S-shaped configuration. The A3 through A5 segments coursed in the
callosal sulcus in 60% of the hemispheres. In a further 32.5% of the hemispheres, they followed an irregular course, and at least one of the
segments coursed in the cingulate sulcus. In the remaining 7.5% of the hemispheres, the A3 through A5 segments coursed in the cingulate sulcus
and were never involved with the corpus callosum (Fig. 4, A-C). Furthermore, in 10% of the hemispheres, the A4 segment crossed the midline
and supplied portions of the opposite hemisphere.
FIGURE 4. Anatomic variations in the course pattern of the pericallosal artery. A, in 60% of the hemispheres, the A3 through A5 segments
course in the callosal sulcus( CS). B, in an additional 32.5% of the hemispheres, they follow an irregular course, and at least one of the
segments runs in the cingulate sulcus (figure shows three variations[ I-III]). C, in the remaining 7.5% of the hemispheres, the A3 through A5
segments course in the cingulate sulcus( CS) and are never involved with the corpus callosum .
In the instances where the A5 segment coursed in the callosal sulcus (65%), its posterior extension followed a cork-screw-like tortuousity,
anastomosed with the posterior pericallosal artery in the splenial region, and formed the dense portion of the pericallosal pial plexus within the
callosal sulcus (Figs. 5D, 10, and 11). Usually, some of the branches arising from this network circled around the splenium and joined the tela
choroidea of the third ventricle, where they anastomosed with branches of the medial posterior choroidal arteries. In 5% of the hemispheres, this
extension continued anteriorly as far as the foramen of Monro.