ees ate Meeenne sectetetebete’ ce Het ne chet HH oe ait : : “ é : ‘ : Be i a ‘ Sy Ss 5 i etek i fen §; a i elutes ne : ‘ : e y feeiela e r 5 Bee ; H : i ete mode t ; ; an i ‘ sh ee i aaa pera i ; : fas rate tt * ret eteta et + th ate Z 3 a % ‘i : se i : : pernas eae ne fate Ht ance tehat ae Be 3 Hr ected fete et 2 ; 5 i e f : : : ate a : i ae : Ba a : ia ee : f fea stich fu tt ets} che tote spetee srs git SERS : sutetalennheteh fie : a debe : maser aticen : co ss} An Atlas of Pathology of the Brain E.E. Payne, M.D. The Welsh National School of Medicine Department of Pathology Cardiff/ Wales Published by SANDOZ 1969 Contents Page Preface i The Normal Brain 2 Hydrocephalus 8 Cerebral Oedema 12 Intracranial Space-Occupying Lesions and Cerebral Herniations 14 Intracranial Vascular Disease 16 Intracranial Neoplasms 30 Intracranial Infections 42 Demyelinating Diseases 48 Degenerative and Metabolic Diseases 50 Congenital Malformations 56 Index of Illustrations 61 Preface This atlas has been designed to present the gross pathological appearance of the brain in a number of disorders which affect this organ. The illustrations have been selected to demon- strate the common and a few of the less common pathological conditions. The legends to the illustrations indicate the general nature of the pathological process shown in each specimen. A detailed explanatory text on each case has been purposely omitted; it was felt that the written word would distract the observer’s attention from the basic pathological features which are self-evident in the illustrations. The nervous system forms the central core of our actions, reactions and responses and as such we are all concerned to learn more about the disturbances which affect it. The delicate mechanism of the brain may be upset by either physiological disturbances, by disorders of the viscera or by disease of the brain itself. On frequent occasions the medical practitioner is cognizant that some temporary derangement of cerebral function is present in his patient, but in many cases he is unaware of the precise pathological process that is being enacted within the nervous system. The com- plexity of the anatomical connections, the physiological proc- esses and the pathological disturbances of the central nervous system make its study something of a speciality. Much detailed research work will be necesssary before many of the common pathological conditions are completely understood. In the meantime this atlas will serve as a reminder of the pathological appearance of the brain in a number of conditions. Most of the disorders illustrated are commonly met in clinical and pathological practice. The few uncommon or rare conditions shown will be of interest to the physician, surgeon or pa- thologist who specializes in the study of neurological dis- orders. Some of the illustrations are of fresh tissue while others are of formalin fixed tissue. The colour of the large thin sections is that seen by the pathologist when he examines a fixed spec- imen; the sections have not been stained. The large thin sections have been reproduced in this atlas at their natural size, allowing the reader to make direct measurements of the dimensions of the lesions. The technique for the preparation of large thin sections of brain mounted on paper The brain is fixed by suspending it from the basilar artery in 6000 ml of 4°/o formaldehyde in water. About one week later the brain is examined and cut into slices in some convenient plane; one slice, between 2 and 5 cm thick, is selected for processing for large thin sections. The selected slice should contain part of the main pathological lesion that is to be studied. If necessary this slice can be placed in fresh fixative for another 5-6 days to ensure complete fixation. When convenient the slice is washed in running water for two days to remove any unbound formalin. The washed slice is em- bedded in warm 25°/o gelatin solution; the gelatin block containing the specimen is affixed by gelatin to the specimen plate of a modified “sledge” large section microtome. The block and plate are placed in a deep-freeze overnight. The specimen plate is bolted to the microtome, the upper surface of the block is painted with warm 7° gelatin solution and large sections of brain are cut at 500 microns thickness. The sections, each separated by a piece of cellophane, are stored in 4°/o formaldehyde solution. When it is convenient to mount the sections they are washed in running water for 3—4 hours. Each large thin section of brain is then mounted between layers of cellophane and backed with a layer of absorbent paper. The layers are built up on a perspex plate and between each layer there is a thin film of mounting solution (7°/o gelatin and 7°/o glycerol in equal parts). Any air bubbles present are removed and the section enveloped in cellophane on the perspex plate is allowed to set for half an hour. The plate is hung in a drying cabinet at 27°C for about 18 hours and then the sections can be peeled off the perspex plate. Serial sections are labelled and can be examined at leisure. The sections provide an accurate record for research pur- poses and a useful aid in teaching. The Normal Brain The appearance of the brain alters between birth and the senilium. In the newborn the brain is soft and grey in colour, the differentiation between the grey and white matter is not distinct. As myelination of nerve fibres proceeds the brain takes on a firmer consistency and the white matter stands out clearly. The main tracts in the brain acquire their myelin by the end of the second year of life, thereafter the myelination process proceeds more slowly. An intact myelin sheath appears to be essential for the proper function of the nerve fibres. The whole process of myelination is completed about the end of the second decade of life wnen some of the associ- ation tracts receive their myelin coat. The brain is fully formed in the young adult and at that stage the weight should be between 1250-1450 g. for the male and 1200-1400 g. for the female. As middle age passes and senescence appears the brain shows slight general reduction in its volume; this is thought to be due to a diminution of its water content. A study of large thin sections of the brain of various age groups shows that in general the brain substance atrophies with increasing age. While the consistency, colour and functional ability of the normal brain alter during life, there is no change in the general shape of the brain structures. The gyral pattern on the external surface of the normal brain shows a slight variation from one case to another. Marked deviation from the normal size and shape of the cerebral convolutions are occasionally seen as a feature of congenital brain anomalies: the gyri may be exceptionally large and smooth with few sulci (lissencephaly) or at the other extreme the convolutional surfaces may be tracered with multiple shallow sulci (micropolygyria). There is very little space between the normal brain and the inner surface of the cranium (Fig. 1). Some common neuro- pathological conditions such as cerebral atrophy and cerebral oedema are most evident when the brain is examined in situ after removal of the skull-cap for it is only at this time that a true comparison can be made between the size of the brain and the capacity of the cranial cavity. The membranes which cover the external surface of the central nervous system help to protect and support the deli- cate nervous tissues. The outermost membrane, the dura, is thick, strong and pliable; it conceals the venous sinuses between its fibrous lamelae at the points where the processes 2 of the membrane project into the skull cavity to form the tentorium cerebellum and the falx cerebrum. The normal arachnoid mater is a thin homogeneous transparent mem- brane; slight thickening of this membrane is a common finding in advanced life. The pia mater, also a thin membrane, is adherent to the brain tissue; the pia with the arachnoid con- stitute the leptomeninges which form the boundaries of the cerebrospinal fluid space. The brain receives its nutriments by way of the carotid and vertrebral arteries; the interconnection of these vessels on the basal surface of the brain forms the Circle of Willis. Three main arteries (the anterior, middle and posterior cere- bral arteries) leave the circle on each side and supply the respective areas of brain tissue. At the peripheral part of their distribution the arteries on each hemisphere form an anastomotic network with each other, producing the so-called “boundary zones” or “watershed areas”. The boundary zone areas of brain tissue are particularly susceptible to haemor- rhagic infarction in hypotensive states. The cut surface of the brain reveals something of the complex architecture of cerebral tissues. The over-folding of the corti- cal ribbon produces the convolutions which tend to be rounded in outline and are separated by narrow sulci. The grey matter of the cortical ribbon and the basal ganglia stand out clearly from the myelinated nerve fibres which constitute the centrum ovale and capsular systems. A sagittal section through the median plane of the brain (Fig. 4) shows the septum pellucidum and parts of the ventri- cular system. For most routine examinations, the brain is cut in the coronal plane (Fig. 5): this plane of section provides the observer with an adequate view of the basal ganglia, ventricular system and the general characteristics of the hemispheres. The cavities of the normal ventricular system are little more than slit-like spaces; in the normal young adult the corners of the ventricles are pointed and the ventricular volume is of the order of 15 to 20 ml. As age advances, the ventricular volume increases to compensate for the slowly progressive reduction in the amount of brain tissue. Transverse section of the brain (Fig. 7) cut through the level of the basal ganglia clearly shows the relative positions of the central masses of grey matter and the slight irregularity in the size of the cerebral hemispheres, the dominant hemisphere (commonly the left) being usually slightly larger than the right. Fig. 1. Vertex of the brain in situ. There is very little space between the normal brain and the cut edge of the skull. When the dura mater is removed the brain sinks downwards and consequently leaves a small space between the brain and the frontal bones. Fig. 2. The base of the brain. The normal arachnoid membrane is transparent and as such does not interfere with the view of the structures at the base of the brain. This view of the brain allows for the examination of the cranial nerves, the major blood vessels, the brain stem and the inferior surfaces of the cerebrum and cerebellum. Fig. 3. Lateral aspect of the brain. The normal brain has rounded contours, the gyri are wide and the sulci are narrow. _. Fig. 4. Medial aspect of the brain. Note that the posterior end of the septum pellucidum tapers to a point (arrowed). Fig. 5. Oblique coronal section. The section passes through the red nuclei which are situated just above the substantia nigra in the mid-brain. Fig. 6. Sagittal section. The large thin section of the brain is cut in the sagittal plane to one side of the mid-line. The cerebral convolutions and cerebellum are clearly shown. The head of the caudate nucleus is prominent. The _ thalamus and substantia nigra can be distinguished. Fig. 7. Transverse section. This cut is through the basal ganglia and the thalamus. The normal ventricular system is seen to be little more than a slit in the brain substance. eee |