Anatomical analysis of the developing cerebral vasculature in premature neonates: absence of precapillary arteriole-to-venous shunts.

Germinal matrix hemorrhage-intraventricular hemorrhage (GMH-IVH) commonly affects premature neonates. The gravity of the consequences associated with GMH-IVH makes it a major concern in their care. GMH-IVH begins in the germinal matrix tissue and is, most commonly, the result of venous rupture. Arteriole-to-venous precapillary shunts in the cerebrum of premature neonates could, if present, lead to elevated venous pressure in the germinal matrix and, thus, would be an important etiological factor. We report an autopsy study, involving 33 cases of premature neonates, designed to determine whether precapillary arteriole-to-venous shunts are present in the cerebral vasculature. Brain tissue was embedded in celloidin, sectioned into 100- micro m-thick slices and stained using alkaline phosphatase enzyme histochemistry, a method that distinguishes afferent from efferent vessels. Our sections, which are ideal for tracing vessels over long distances and for displaying patterns of branching and connections with other vessels, indicate that precapillary arteriole-to-venous shunts are not a major influence on cerebral blood flow in babies born at 23 wk gestation or later. The cerebral vasculature in one baby, who died at 24 wk postconception, included shunt-like connections, whereas in 34 babies shunts were not identified. We conclude that precapillary arteriole-to-venous shunts are not a significant factor leading to GMH.