Ove Hassler

Angiographic and Histologic Changes in Infundibular Widening of the Posterior Communicating Artery

The proximal part of the posterior communicating artery is often funnelshaped at its origin from the carotid siphon and may vary considerably in size and outline (ref. 4, Fig. I). In some cases in which the posterior communicating artery has not been filled, a broad-based varying bulge in the wall of the carotid siphon may be evident at the site where the posterior communicating artery arises (ref. 4, Fig. 2). A survey ofa normal material of 1020 angiographies (angiographies without evidence of other vascular changes) revealed bulging of the vessel wall at the typical site in 67 cases (SALTZMAN). Approximately the same incidence was established in a material comprising 223 cases of intracranial expansive processes and 118 cases of arterial aneurysm in the carotid region. The figures correspond to ten per cent of the carotid angiographies in which the posterior cerebral artery was not demonstrated. The appearance of the bulge corresponded in many cases with the funnel-shaped proximal part of the posterior com-

The windows of the internal elastic lamella of the cerebral arteries.

The large cerebral arteries have a relatively thick, compact internal elastic lamella in which small windows occur. The nutrition of the tunica media takes place by diffusion from the lumen, because the normal cerebral arterial wall generally has no vasa vasorum. The main part of the nutritional transport probably goes through the windows because the compact portions of the elastic lamella are less permeable. The windows may thus constitute narrow gateways facilitating the passage of nourishment to the media. With increasing age the windows get smaller and less frequent at the same time as the elastic lamella increases in thickness. In the largest cerebral arteries these windows were also found to be smaller than in the cerebral arteries with a finer calibre. With increasing age the nutritional supply to the media may therefore be endangered in the largest cerebral arteries, expecially since the media of these arteries needs a greater supply than that of the smaller ones. When the nutritional transport is insufficient media fibrosis and atheromatosis may develop. These lesions are actually most common in the largest arteries. Die großen Hirnarterien haben eine relativ dicke, kompakte Lamina elastica interna, in der kleine Fenster vorhanden sind. Die Ernährung der Tunica media geschieht durch Diffusion vom Lumen aus, da die normalen Hirnarterien gewöhnlich keine Vasa vasorum besitzen. Der größte Teil des Stofftransportes geht wahrscheinlich durch die Fenster, da die kompakten Teile der Lamina weniger durchlässig sind. Die Fenster stellen also einen Zugang dar, der den Transport zur Media erleichtert. Mit zunehmendem Alter werden die Fenster kleiner, ihre Anzahl verringert sich, gleichzeitig wird die Lamina dicker. Die Fenster der großen Hirnarterien sind kleiner als diejenigen der Arterien kleineren Kalibers. Mit zunehmendem Alter kann deshalb der Stofftransport zur Media in den großen Arterien gefährdet sein, besonders da die Media in diesen Arterien eine größere Stoffzufuhr verlangt als die Media in den kleineren Arterien. Bei nicht ausreichendem Stofftransport kann sich Mediafibrose oder Atheromatose entwickeln, Veränderungen, die tatsächlich häufig in den großen Arterien vorkommen.

Elastic tissue contents of the medial layer of the cerebral arteries. Differences between young and adult individuals.

In contrast to previous reports, a high content of elastic fibrils in the media of the cerebral arteries was found in children relative to that in the middle-aged individuals examined. The highest contents were found in subjects between 1 month and 2 years of age. More elastic fibrils were found per volume of media in the internal carotid and basilar artery than in the middle cerebral artery. Im Gegensatz zu früheren Untersuchungen konnte der Verfasser in den Gehirnarterien von Kindern vermehrt elastische Fasern nachweisen gegenüber den Gehirnarterien von Erwachsenen. Die meisten elastischen Fasern wurden bei 1 Monat bis 2 Jahre alten Kindern nachgewiesen. In der A. carotis interna und basilaris waren pro Volumeneinheit mehr elastische Fasern zu finden als in der A. cerebri media.

Functional anatomy of contraction of the large cerebral artery. A preliminary report.

Spastic contraction of the cerebral arteries has acquired increasing interest in clinical literature during the last decades, although many authors continue to doubt its existence (Naess, 1958) . The massive neurosurgical and roentgenological evidence of spasm in the large cerebral arteries within the first weeks following rupture of a saccular aneurysm proves its existence beyond question (Ecker & Riemenschneider, 1951). It is most likely that intense meningeal irritation induces the spasm which operates as a protective mechanism to prevent further haemorrhage. Spasm in connection with ruptured aneurysm is regarded as having great practical importance in that it probably prevents early surgical intervention on bleeding aneurysms (Nor1Cn & Olivecrona, 1952; Pool, Jacobson & Fletcher, 1958). Several recent authors (Krayenbiihl, 1960; Corddy, Rothenberg & Irving, 1961) have maintained that apoplectic insults may be caused by spasin in the large cerebral arteries. Krayenbiihl reports three cases with angiographically demonstrated spasm causing haemipegia and aphasia.

MEDIA DEFECTS IN INTRACEREBRAL ARTERIES

Brains obtained from 20 necropsies were used. The individuals were chosen at random from a number aged between 20 and 50 years and examined within 18 hours of death in the Department of Pathology of Uppsala University Hospital. The brains were carefully removed in entirety. Fifteen brains were fixed by injection of formalin into the internal carotid and vertebral arteries. The remaining five brains with the arteries intact were placed for one week in a large jar containing Bouin’s fixative. After fixation the brains were divided into small pieces which were placed in a low jar containing water under a stereomicroscope. The largest intracerebral arteries within each piece were then carefully dissected free from the brain parenchyma. The arteries were embedded in paraffin, serially sectioned, and stained with various elastin and general stains.

Media defects in the cerebral arteries differences in microscopical structure between neonates and adults

SummaryIntracranial, saccular aneurysms are formed at the site of congenital media defects. A possible factor contributing to the late development in life of aneurysms is that the arterial wall is much thinned out over media defects in adults, whereas in neonates the total thickness of the arterial wall is not very much decreased at the site of media defects.ZusammenfassungDie sackförmigen Aneurysmen der Hirnarterien entstehen an jenen Stellen, an denen sich für gewöhnlich kongenitale Mediadefekte finden. Ein Umstand, der dazu beiträgt, daß sich Aneurysmen erst im späteren Leben entwickeln, ist die starke Verdünnung der Arterienwände oberhalb der Mediadefekte bei Erwachsenen; bei Kindern sind die Arterienwände an diesen Stellen nicht so stark verdünnt.