Anterior Cerebral Artery

The anterior cerebral(Fig. 31) passes forward and inward over the anterior perforated space, between the olfactory and optic nerves, to the median fissure. It gives off the anterior communicating artery at this point, which joins the anterior cerebral of the opposite side. The main trunk then runs upward in the longitudinal fissure on the corpus callosum, giving branches to the frontal and parietal lobes, and finally anastomoses at the posterior end of the corpus callosum with the posterior cerebral. This shows the wide extent of brain tissue on the medial surface of the brain which would be affected by the blocking of this vessel by an embolus.

The terminal branches of the anterior cerebral spread laterally over the surface of the brain (Fig. 32) outward from the longitudinal fissure for a short distance, about 2 cm. As it crosses the anterior perforated space, it gives off the anteromedian perforating (ganglionic) arteries which pierce the lamina cinerea to supply the anterior portion of the caudate nucleus above.

Middle Cerebral Artery

The middle cerebral artery passes upward and outward in the fissure of Sylvius, dividing, when opposite the island of Reil, into the branches which supply the cortex of the brain (see Fig. 32). On its way toward the island of Reil, at the commencement of the fissure of Sylvius, many small straight branches enter the brain substance to supply the basal ganglia. Two or three supply the caudate nucleus, others, called the anterolateral perforating (ganglionic), enter the anterior perforated space to supply the lenticulostriate ganglion and the anterior portion of the thalamus. One of the largest of these arteries, the lenticulostriate, has been called the artery of cerebral hemorrhage, by Charcot, on account of the frequency with which it is found ruptured in cases of apoplexy (Fig. 33).

Fig. 34.   Showing the degenerative and apoplectic areas of the brain and the course pursued by the motor fibres from the cortex, through the internal capsule, crura, pons, and medulla to the decussation, where they cross the median line to supply the opposite side of the body.

Fig. 34. - Showing the degenerative and apoplectic areas of the brain and the course pursued by the motor fibres from the cortex, through the internal capsule, crura, pons, and medulla to the decussation, where they cross the median line to supply the opposite side of the body.

Anterior Choroid

The anterior choroid artery comes sometimes from the internal carotid and sometimes from the middle cerebral. It passes backward and outward on the optic tract and crus cerebri and enters the transverse fissure at the descending horn of the lateral ventricle. It ends in the choroid plexus (see Fig. 33).

Posterior Cerebral Artery

The posterior cerebral artery passes outward over the crus cerebri, just above the pons, to the under surface of the posterior portion of the cerebral hemisphere. Before it receives the posterior communicating artery it gives off the posteromedian perforating (ganglionic) arteries, which enter the posterior perforated space to supply the thalamus and third ventricle. Just beyond the posterior communicating artery it gives off the posterolateral perforating (ganglionic; arteries, which supply the posterior portion of the optic thalamus, crus cerebri, and corpora quadrigemina. The branches to the cortex supply a small portion of the inferior surface of the temporosphenoidal lobe and the occipital lobe as seen in Figs. 31 and 32.

Fig. 35.  Medial section of the brain.

Fig. 35. -Medial section of the brain.

Fig. 36.   Horizontal section of brain; the corpus callosum and fornix have been removed, exposing the lateral ventricles, with the caudate nuclei projecting into them anteriorly and the velum interpositum farther back, with the choroid plexus at the sides and the veins of Galen nearer the middle line. The lateral ventricles in this brain are somewhat larger than usual.

Fig. 36. - Horizontal section of brain; the corpus callosum and fornix have been removed, exposing the lateral ventricles, with the caudate nuclei projecting into them anteriorly and the velum interpositum farther back, with the choroid plexus at the sides and the veins of Galen nearer the middle line. The lateral ventricles in this brain are somewhat larger than usual.