Origin of the perforating arteries of the interpeduncular fossa in relation to the termination of the basilar artery.

We studied the perforating arteries of the interpeduncular fossa in 100 human brains which had previously been embalmed and injected with coloured intravascular neoprene latex. Three groups of perforating arteries were observed: the short interpeduncular arteries, a group of very fine arteries which can originate on every artery in the interpeduncular fossa and are destined to the cerebral peduncles and the oculomotor nerves (III); the diencephalic arteries, larger in diameter, most of which supply the mamillary bodies; only a few of them (one or two) penetrate the diencephalic floor and reach the posterior limb of the internal capsule and the anterior and medial thalamus; the diencephalic arteries are either individual branches of the PI segment of the posterior cerebral arteries (PCA) or stem from the same segment of the PCA via a trunk common to the mesencephalic arteries; the latter supply the mesencephalic area medial to the pars reticularis of the black substance. Our study focusses on where the diencephalic and mesencephalic arteries originate, based on how both anterior longitudinal neural arteries merged into a basilar artery in the embryo. When merging was symmetrical, whether in the early stages or later, the origins are more or less equally distributed; however, when merging was asymmetrical, the great majority of the perforating diencephalic and mesencephalic arteries stem from the P1 segment on the side that merged earliest (cranially).