Basilar bifurcation: a comparison of prenatal and postnatal cases

Study investigates and compares the reliability, of basilar bifurcation geometry obtained by microdissection, conventional geometrical models of the fetal cerebral arterial circles (CACs) and, the results of current angiographic and experimental studies on adult humans present in the accessible literature. Hundred CACs were selected from 200 fetal brains. All fetuses were free from any macroscopically visible malformations. The lengths and outer diameters of precommunicating parts of the posterior cerebral arteries (P1s), as well as D1, D2 and D3 distances in each of the CACs were measured with an ocular micrometer. The construction of CAC models and measurement of basilar bifurcation angle were performed on the paper with conventional instruments. Basilar bifurcation angle ranged from 35 to 175 degrees. Almost two thirds of the cases had the angle larger than 90 degrees. The P1 length did not influence on average basilar bifurcation angle. Perforating branches originated from basilar bifurcation in 7.3% of the cases; the oculomotor nerve had direct contact with the basilar bifurcation in 2.9% of 68 fetuses. It may be freely concluded that there is ‘copying’ of fetal basilar bifurcation vascular geometry into the adult pattern and, vice versa. Basilar bifurcation angle represents predominant form of bifurcation, and this led us to assume that it represents as a marker of optimal vascular geometry, and the presence of aneurysms might lead to the basilar bifurcation angle deformation more frequently in cases having an acute basilar bifurcation angle.