The vascular architecture of the human cerebral deep white matter was studied using soft X-ray and diaphanized specimens, achieved by intra-arterial injection of barium and vascular stain respectively, and also by electron microscopic examination of the corrosion cast of arteries in normal adult brains. The deep white matter arteries passed through the cerebral cortex with a few branches to the cortex and ran straight through the white matter. The arteries concentrated ventriculopetally to the white matter around the lateral ventricle. Anastomoses were noted around the ventricular wall at the terminals of the deep white matter arteries. No centrifugal branches irrigating the periventricular white matter from the lenticulo-striate arteries were observed in the present study. The presence of anastomoses among the terminal branches of deep white matter arteries protects against ischemic change or infarction in this area from an occlusion of a single deep white matter artery. This may lead to development of terminal zone infarction from ischemia or vascular diseases, affecting multiple deep white matter arteries. The subcortical and deep white matter arteries had thick adventitial sheaths and large adventitial spaces in the white matter but not in the cortex. The presence or absence of the adventitial space is regarded as another characteristic difference between the arteries in the white matter and cortex. This difference may influence pathological changes in vascular lesions in these respective areas.

The microvascular architecture of the human cerebral subcortical white matter was studied. Most of the subcortical arteries ran straight through the cortex, but upon entering the white matter, they began to coil, loop, and spiral. Vascular stains showed wide spaces between the adventitial sheaths and blood vessels. The blood vessels coiled, looped, and spiraled within these wide adventitial spaces. This phenomenon was observed in the brains from persons ranging from the first to ninth decades of life and there were no statistically significant age-related correlations. Furthermore, there was no evidence of a reduction in the volume of white matter after fixation. Therefore, the observed tortuosity does not appear to be the result of shrinkage of brain tissue following fixation. While the mechanisms responsible for the subcortical arteries circuitry remain undetermined, this coiling architecture may serve as a trap for tumor cells and microorganisms passing through the blood stream, suggesting that these coiling arterial blood vessels may play a significant role in the pathogenesis of tumor metastasis and the brain abscess that frequently occurs in the gray-white matter junction.

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In the present study, the human cerebral meninges were rich in blood vessels, but no capillaries were noted. The meningeal arteries ran over the veins where they crossed. Several arterial anastomoses existed on the cortical surface. The meningeal arteries were classified into four parts; the conducting artery approximately 700 microm in diameter, distributing artery approximately 200 microm in diameter, precortical artery approximately 60 microm in diameter and cortical artery approximately 30-40 microm in diameter. A single distributing artery supplied the area of approximately 3.5 x 2.0 mm on the brain surface. They further ramified into precortical arteries which stemmed cortical arteries. These precortical arteries had the distributing area of 1 mm2 and this distributing area was the same size as the width of human ocular dominant column of the visual cortex. Constriction, like a sphincter, was observed at the bifurcation of the distributing arteries. The cerebral blood vessels, which regulated the blood flow and reacted to autonomic nerve stimuli, seemed to correspond to the distributing arteries.

The microvascular architecture of the basal ganglia of human brains was studied on diaphanized specimens after intravascular barium injection and vascular stains. Observation by scanning electron microscope was also performed. The putamen and caudate nucleus showed dense capillary networks. Less dense capillary networks were noted in the capsula interna. The capillary network in the globus pallidus was less dense than that in the striatum but denser than that in the capsula interna. The lenticulostriate arteries ran through the putamen, across the internal capsule and reached the caudate nucleus. Though the arterial branches running within the putamen had many small branches, branching was minimal while crossing the capsula interna and began showing rich ramification again when they reached the caudate nucleus. There were retrograde ramifications in the putamen and caudate nucleus. They appeared to play a signiscant role in the regulation of blood pressure and are considered to play some role in the occurrence of circulatory disturbances which are prone to involve these structures. The fountainlike ramifications were seen in the putamen and caudate nucleus, but their function is not clear. In the brains of senile patients, intertwining of the arterial blood vessels was noted in the fountain-like rami. This structure began to appear in the patients over the age of 50. While the etiology of the intertwining of the arteries remains unknown, its increasing frequency with age supports a hypothesis that this represents a phenomenon correlated with aging or concomitant brain atrophy.