Origin of intraventricular haemorrhage in the preterm infant.

A technique has been developed for the injection and stereomicroscopic examination of blood vessels in the preterm newborn brain. Using this technique it can be seen that in the immature brain there is a rich capillary bed in the germinal layer region supplied mainly by Heubner's artery. Capillary channels drain directly into the terminal vein and its main branches. Study of 19 cases with spontaneous germinal layer haemorrhage (GLH) with or without intraventricular haemorrhage (IVH) failed to show rupture of the terminal vein or germinal layer infarction. In babies of up to 28 weeks' gestation GLH developed most frequently over the body of the caudate nucleus, whereas in babies of 29 weeks' gestation or more the haemorrhages were usually over the head of the caudate nucleus. Histological study of 10 cases of GLH failed to show rupture either of arteries or veins, though evidence of rupture at a capillary-vein junction was seen in one case and masses of fibrin adjacent to the vein wall in 2 others. Injection through the carotid artery caused prominent leaks of injection mass within the germinal layer capillary bed, often adjacent to the veins. Injection through the jugular veins in 2 cases failed to rupture the terminal vein but caused multiple vein ruptures at the junction of deep and cortical venous systems. Additional small ruptures in the germinal layer occurred in one of the cases only. It is suggested that the capillaries within the germinal layer may be ruptured by a rise in arterial pressure, particularly in conditions of hypercapnia and hypoxia.