SUBDURAL HEMATOMA (Experimental Investigation of Membrane Formation) by M. Gueramy, M.D. A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Master of Science. Department of Neurology and Neurosurgery, McGill University, Montreal. April 1964 TABLE OF CONTENTS Page I. INTRODUCTION II. HISTORICAL REVIEW A. Anatomy of Dura and Subdural Space l B. Pathology and Mechanism of Chronic Subdural Hematoma 7 C. Radio-isotope Studies 13 D. Experimental Studies 17 III. EXPERIMENTAL STUDIES A. Experimental Design 24 B. Morpho1ogical Studies 28 a) Methods and Materials 28 b) Results 29 C. Radio-isotope Experiments - Cats 31 a) Methods and Materials 31 b} Results 35 D. Radio-isotope Studies - Human 40 a) Methods and Materials 40 b) Results 49 IV. DISCUSSION 53 V • SUMI'v1AR Y 59 VI. BIBLIOGRAPHY 61 VII. ACKNOWLEDGEMENTS 65 I. INTRODUCTION Subdural haematoma was one of the first neurological lesions to be treated by man. Prehistoric man performed trepanation. Later, Hippocrates and Galen described cases with recovery after evacuation of clot which were probably subdural haematomas. As the science of medicine evolved over the centuries, investigators have argued about the etiology of this lesion. Up to now many questions have been answered. But in spite of modern knowledge of anatomy and physiology, the mechanism of chronic subdural haematoma remains obscure. This study was undertaken to add more basic knowledge to this essential question. Attempts were made to produce experimental subdural haematomas in animals. Radio-isotopes were used to trace the route of absorption of haematoma in animals and as a diagnostic aid in detecting lesions in human cases. 1. II. HISTORICAL REVIEVJ A. Anatomy of the Dura and Subdural Space In 1875 Key and Retzius presented a comprehensive and thorough work on the macroscopic and microscopie structure of all three meninges, which may be summarized as follows: The dura mater of the brain consists of two layers of connective tissue fibrils with intermediate cells, most of which are filiform, lying parallel with the longitudinal direction of the fibrils, and arranged in rows in the tissue spaces between the bundles of fibrils. In the inner layer the main direction of the connective tissue fibrils on the convex side is anteromedial-posterolateral. In the outer layer the bundles are more interwoven, but their main dir­ ection is perpendicular on the inner layer. The two·layers are connected mutually with bundles of fibrils, crossing from one layer to another. Between these collagen fibrils, sorne elastic fibres are seen, most at the base of the skull, least on the convexity. These two membranes cannot always be separated. The blood supply of the dura is described very precisely. The outermost fibrillary layer of the dura contains arteries as well as veins; the arteries run in looping streaks, accompanied by two veins which open into 2. the superior sagittal sinus. The arteries as well as the veins form anastomoses, the vessels branching dichotomously. Fine capilleries and arteries run obliquely through the dural tissue to the inner side where a pattern of long­ meshed capillary net is found, the junctions of which form ampullary blood-filled dilatations; and these ampullary dilatations constitute the connecting link between the capillary and venous systems. On the outer aspect a more open capillary network is seen; and at the transition between the two capillary layers a few tiny vessels are seen. The separation between the capillary nets is most distinct in the parietal region, which also has the richest blood supply. By injection into the dural tissue, Key and Retzius succeeded in filling a rather dense-packed tubular system running parallel with the fibrils. But they found no endothelial lining of these spaces, on which account they did not regard them as lymphatics proper but merely as a system oÏ "juice channels". They further mentioned that the inside of the dura on both sides of the various sinuses, especially around the superior sagittal sinus, is equipped with a system of traveculae. In man, but not in dog or ether animal species, they demonstrated the so-called lacunae, differing in form and size, but without any parti­ cular lining outside the elastic membranes. In spite of repeated attempts they were only able to fill the lacunae by injections into the "juice channel nsystem and into the circulatory system. Huguenin in 1877 thought the blood supply was far more abundant in the outer leaf of the dura than in the inner, but otherwise he agreed with Key and Retzius. In 1914 Weed stated that endothelial-lined lymph ' spaces were entirely absent from the entire central nervous system, including the meninges. In 1924 Jacobi, and later Zehnder arrived at the opposite result; the dura contained lymph spaces communicating with a subdural space, the peri­ vascular lymph spaces and the venous ampullae. These findings have been contested by Pfeifer in 1928, who states that the vascular walls of the venous ampullae are very thin and friable, on which account he considered the demon­ strated communications artefact. He also denied the presence of endothelial-lined lymph spaces, whereas he recognized a ffjuice channel" system between the dural fibrils. An exhaustive description of the vascularisation of the dura was given by Pfeifer (1930) who injected the blood vessels as soon as possible after death, simultaneously with fixation of the brain and meninges in situ. The injected vascular apparatus was examined under a stereo­ scopie microscope, so that mistakes concerning the relative depth of the location of the vessels could be avoided. In the most superficial layer, as demonstrated previously, there is a capillary network with wide elongated meshes and vessels of fine caliber which are anastomosing with the diploic vessels but otherwise are provided with blood from the meningeal arteries, and many of them open directly into the underlying venous-capillary system. Then, at a deeper plane, come the large, markedly winding, menin­ geal arteries, each with two concomitant veins of quite irregular width and form, which - without any sharp border - continue in the thin-walled venous sinuses. Like several previous investigators, Pfeifer observed on the inside of the dura another, superficial, extensive capillary network, curly and necklace-like in appearance, which undoubtedly has contributed to their interpretation by earlier investigators as lymphatics (when the blood was evacuated). The thinness of the vascular wall is suggestive of great capacity for transudation and absorption on the inside of the dura, and the irregular calibre must have consequences in the circulatory regulation of the dural vessels. Erna Christensen (1941) investigated the thickness and vascularisation of the dura and her findings were similar to previous investigators. In the external layer layer of the dura, besides the larger vessels she found a polygonal capillary net in which the meshes average half a milimetre in width, and most of the capillaries measure 5u in diameter, though a lumen of lOu is encoun­ tered here and there. Sections from the middle of the dura present a few vessels. In the inner layer the capillaries again are numerous, forming a network with long meshes and most of the capillaries are running parallel with the fibrils with a few oblique anastomosis. The subdural space had been accepted as a potential space till Penfield in 1924 performed some experimenta in order to settle the question whether the subdural space is a truly potential space or normally contains fluid. In his experimenta anaesthetized dogs were given an injection of ten percent Formalin into the interna! carotid at a pressure of two hundred centimetres. The animals were at once placed in a refrigerator at a temperature of zero centigrade. After five to fifteen days the head was divided into frontal sections with a saw. The total bulk of the brain could then be pushed out of the sections together with the pia and arachnoid, as well as a coat of ice, clear as water in the subarachnoid space. The dura was left on the inside of the skull and on the inner 6. surface of the dura a la of clear yellow ice was spread over both hemispheres, varying in thickness from one half to one millimetre thinnest over the There was sorne individual variation in the thickness of this layer of ice in the dogs examined. Thus it was proved that normally, at any rate in dogs, there is a smdll amount of fluid in the subdural space, and that it is not id cal with the fluid found in the subarachnoid space. e findings prove that normally there is a 1 amount of fluid in the subdural sp::J.ce, that the com­ position of this fluid differs from that of the cerebro­ spinal fluid in the subarachnoid space. B. Pathologx and Mechanism of Chronic Subdural Hematoma Early investigators agreed on the microscopie de- s ption of the subdural hematoma, but held wid di- vergent opinion r ing the iology and pathogenesis of this condition. Before 1855 the disease was regarded as resulting from hemorrhage betvJeen the meninges. 1''1organgi (1765), Abercrombie ( 1829), and Raki tans ky ( 1844) thou~~ht the lesion was a result of hemorrha c cysts between the dura and arachnoid, whereas Bayle (1826) claimed that the hem- arase between the dura and a pseudomembrane on the de of the dura. Rokitansky scribed the lesion as a ing spindle s~aped unila structure, localized to the parietal re on, and consisting of rust colored, vascularized membrcmes which had fused with the external of the arachnoid_and with the dura. The structure of the membrane corresponded to blood undergoing organ­ ization. Literature from 1817-1854 reflects the on of many authors that the membranes originated from the clot- t and organization of the accumulations of blood in the 11 arachnoid sac." In 1855 Heschl disagreed with previous viewpoints and said that blood shed into the subdural space over the convexity would sink to the base of the skull, thus could not be the cause of the usual fo~m of the chronic subdural hematom0 over the convexity of brain.