ATROPHY AND HYPERTROPHY OF THE BRAIN.
BY H. D. SCHMIDT, M.D.
ATROPHY OF THE BRAIN.
INTRODUCTION AND DEFINITION.—Atrophy of the brain may originate during intra-uterine life or by defective development during the early periods of childhood, or it may occur during adult life, when the organ is fully developed. The atrophy is characterized by a diminution of the normal bulk of the brain-substance, in consequence of which the latter does not entirely fill the cavity of the cranium, but leaves a greater or less space to be occupied by a serous fluid. Generally, the atrophy affects, in a symmetrical or asymmetrical manner, larger or smaller portions of the brain; an atrophy symmetrically affecting all parts of the brain has never been observed, even in microcephalia. Nevertheless, when the atrophy affects both hemispheres of the cerebrum, it is generally called total, whilst it is designated partial when it is limited to only one hemisphere or to other individual parts of the brain, such as the cerebellum, the large cerebral ganglia, etc.
For the sake of convenience we shall treat the atrophy of the brain occurring during childhood, when the organ is still developing, separately from that of the fully-developed brain of the adult.
1. Atrophy of the Brain during Childhood.
When congenital or originating during infancy the atrophy is either primarily due to certain pathological processes taking place in the substance of the brain, or secondary, being due to lesions of the skull, such as premature ossification of the sutures. Total atrophy of the brain at this period of life leads to an early death, while children affected with partial atrophy may continue to live, though almost always in a state of idiocy. The forms mostly observed in children are unilateral or bilateral atrophy of the cerebrum, partial or almost entire absence of the cerebellum, imperfect development of the large cerebral ganglia, and slight partial atrophy of the medulla oblongata. The large commissures as well as the crura cerebri are very seldom found atrophied.
The most frequent and, from a practical point of view, the most important of these forms is the unilateral atrophy of the cerebrum, for the reason that in a mild form it is to a certain degree consistent with the mental and physical development of the child. It is mostly found on the left side. In some cases the atrophy extends evenly throughout the hemisphere, while in others it affects more or less one or the other lobe. The loss in the bulk of the hemisphere may amount to only a slight diminution, or to as much as to one-half of the normal size. Its thickness above the ventricle may be reduced to a few millimeters; in some cases even the membranes of the brain may lie in contact with the ependyma. The ventricle of the atrophied hemisphere is almost always enlarged. The convolutions of the cerebrum are very narrow, sometimes quite indistinct. One or both of the corpora striata also are generally found atrophied. In many cases even the atrophy extends to one of the crura cerebri and to the pyramid of the same side, and to the anterior and lateral columns of the spinal cord on the opposite side. Frequently, one or the other lateral half of the cerebellum also is found affected. The condition of the substance of the cerebrum is nearly the same as in the senile atrophy of the brain to be described hereafter. The skull is mostly thickened on the side of the atrophy, and frequently asymmetrical.
SYMPTOMS.—In most cases the mental capacity is below the normal standard, and frequently borders on or represents a state of idiocy. The temperament of the patient is generally irritable and very excitable. The most prominent symptom is an incomplete paralysis on the side opposite to the atrophied hemisphere, which is the more pronounced the more the corpus striatum, thalamus opticus, and crus cerebri are involved. Frequently, there are contractures of the flexor and pronator muscles of both extremities, particularly of the upper; the muscles of the trunk remain free; sometimes one or the other half of the face is also paralyzed. Epileptic convulsions also are frequently present. Blindness and deafness, with a defective sense of smell and a blunted sensibility of the paralyzed limbs, as well as neuralgia of the latter, and headache, have also been observed.
CAUSES.—Besides the causes already mentioned, atrophy of the brain occurring in children after birth may be induced by injuries of the head, inflammation of the enveloping membranes, of the ependyma, or of the substance of the brain itself.
TREATMENT.—Atrophy of the brain in children is perhaps, in the majority of cases, incurable; it is therefore only in the milder cases that the patient may be benefited by treatment. Electricity and gymnastic exercises have been recommended. At any rate, it must be pursued in a very systematic manner, and based upon the principles established and practised by the late E. Seguin of New York in his Physiological School for Weak-minded Children, consisting in improving the mind, first by training the child to the use of his limbs by means of light mechanical work, etc.
2. Atrophy of the Fully-developed Brain.
In the brain of the adult the atrophy may be partial or total, symmetrical or asymmetrical, in the same sense as before used in connection with the atrophy of the brain of children. It may, further, be stationary, when the atrophying process remains limited to the part where it originated; or, progressive, when it extends to other parts of the brain. Generally, partial, asymmetrical, and stationary atrophy is due to certain accidental pathological processes, producing a destruction or loss of portions of the substance of the brain, such as apoplexy, softening, etc., by which the nutrition of the neighboring parts becomes disturbed. Total, symmetrical, and progressive atrophy, on the other hand, actually depends upon certain constitutional disturbances of the nutritive process in general, such as chronic alcoholic intoxication, etc.
CAUSES.—As already mentioned, the causes of atrophy of the brain in the adult may be direct or indirect. The former are generally represented by certain pathological processes which directly affect the substance of the brain, as, for instance, apoplectic hemorrhagic effusions into the brain-substance, thrombosis or embolism of the cerebral arteries, encephalitis, chronic serous effusions into the ventricles, inflammation and œdema of the pia mater, etc. To the latter or indirect causes, which affect the organ by disturbing or lowering the nutrition of its substance, belong the retrogressive processes of old age or of insanity; the introduction into the system of certain noxious substances, such as lead or alcohol; furthermore, certain wasting diseases, such as phthisis, Bright's disease, etc.
PATHOLOGICAL ANATOMY.—The cerebrum particularly is found diminished in volume. While the convolutions are thinner than normal, their intervening sulci are broader. The white substance presents a dirty-white color, and is abnormally dense and tough, especially near the ventricles. The latter are enlarged and filled with serum; their ependyma is thickened and frequently covered with granulations. The cortical layer appears of a dirty, rusty-brown or yellow color, is pale, soft, or hard, and frequently is found to adhere to the pia mater. In very pronounced cases the white substance is almost as tough as leather, and contracts upon section, especially in the convolutions; its cut surface is rendered concave. Sometimes the surface of the convolutions, after the removal of the pia mater, appears finely shrivelled. The dura mater is often found thickened and adhering to the skull. The space created in the cavity of the cranium by the atrophy of the brain is filled by serous effusions into the tissue of the pia mater, the subarachnoidal space, arachnoid sac, and ventricles.
The histological changes associated with atrophy of the brain differ in the different forms. In cases of partial atrophy caused by hemorrhages, etc. the destructive process generally embraces all the tissues at first, while the secondary degenerations particularly affect the nervous elements. In total atrophy the pathological process appears to commence in the connective tissue, and to involve the nervous elements subsequently; though in a number of cases, especially of senile atrophy, the nervous elements appear to be primarily affected. The blood-vessels also undergo certain changes, giving rise to the contraction of the brain-substance.
SYMPTOMS.—In partial atrophy of the brain the primary symptoms resemble those which characterize the particular destructive process to which the atrophy is due. The most prominent are the symptoms of motor disturbance, which are always semilateral and correspond to the extent and seat of the lesion; frequently they remain stationary. The sensibility of the paralyzed parts is but slightly diminished, and the mind generally undisturbed. But when the effects of the original lesion extend, in the form of a secondary degeneration of the nervous elements, to neighboring parts, or even to the other hemisphere, the cerebral functions may become secondarily disturbed.
In senile atrophy of the brain, which represents the most simple form of total atrophy of this organ, the first symptoms frequently appear toward the end of some intercurrent disease. They consist in a very slow and gradually increasing derangement of the cerebral functions, associated with a general loss of innervation, manifesting itself by talkative wanderings of the mind, restless sleep, hallucinations, foolish activity, attacks of tremor senilis, etc. The intellectual functions diminish and the memory is lost. The physical forces also gradually sink, the tremor senilis increases, and the patient, no more able to walk, becomes confined to bed. Finally, a relaxation of the sphincters takes place, and death is produced by the disturbance of the automatic functions of deglutition and respiration.
Total atrophy of the brain, when due to an extensive meningitis or to a general disturbance of the nutrition, as is met with in drunkards, may finally lead to a condition known as general paralysis of the insane. This disease, however, will be found treated elsewhere in this work.
TREATMENT.—There is no special treatment for atrophy of the brain; all that can be done is to palliate and combat the symptoms as they arise.
HYPERTROPHY OF THE BRAIN.
INTRODUCTION.—Notwithstanding the numerous measurings and weighings of human brains made in the course of time by different investigators, no absolute standard measure or weight has as yet been established by which we can accurately determine a pathological increase or decrease in the size and weight of this organ. The want of such a standard is principally due to the difference generally existing in the dimensions and weights of even a certain number of brains taken from individuals belonging to the same race or nation. The same difficulties are met with in the attempt at establishing a rule by which to measure the mental capacity of a certain brain, for the question has as yet not been solved whether this capacity depends upon the quantity or quality of the brain-substance. In speaking of hypertrophy of the brain, therefore, we must keep in mind that a large brain must not be considered hypertrophied unless there exists a disproportion between its size and that of the cavity from which it was removed; in other words, when its growth or hypertrophy meets a resistance at the inner walls of the cranial cavity. According to Virchow, a further distinction must be made between the increase (hyperplasia) of the nervous elements themselves and that of the supporting connective tissue, the neuroglia. To the latter condition particularly corresponds the peculiar doughy consistence of the white substance of hypertrophied brains.
ETIOLOGY.—Hypertrophy of the brain is sometimes congenital, and then associated with dwarfishness and a defective development of the cranium. Generally, however, it is an extra-uterine affection, originating mostly during infancy and childhood, though it is also met with at the age of puberty, and even in adult life. The male sex is more predisposed to the affection than the female. When hypertrophy of the brain occurs during infancy, it is almost always associated with an excessive development of the lymphatic glands, with a defective involution of the thymus gland, and with rachitis, but generally without cachexia. No special exciting cause can be assigned to the affection during youth or adult age, though it has been stated that during these periods of life the disease may supervene upon tubercle or carcinoma of the brain. Repeated active or passive congestion (Rokitanski, Andral), as well as the introduction of lead into the system, has also been supposed to incite the disease.
PATHOLOGICAL ANATOMY.—Directly after the removal of the vault of the cranium, and on cutting through the dura mater, the brain, as if liberated from pressure, is observed to swell out to such a degree as to render the replacement of the removed skull-cap impossible. The enveloping membranes are found closely adapted to one another and to the brain; they are very thin, bloodless, and dry, and their vessels are empty and pressed flat. The hemispheres of the cerebrum are large, and their convolutions, mutually pressing against one another, are flattened at their surfaces, so that the intervening sulci are hardly recognizable. After the removal of the brain from the skull the abnormal dimensions of the cerebrum present a remarkable contrast to the normal size of the cerebellum, pons, and medulla oblongata, which also appear flat and broad from pressure. When a horizontal section is made through the hemispheres of the cerebrum and a little above the corpus callosum, the centrum ovale appears unusually large. The cavities of the ventricles are very narrow, their walls touching one another. There is no serum in the pia mater or in the ventricles. The substance of the brain is pale, bloodless, and dry. The white substance, upon which the hypertrophy particularly depends, is of a doughy consistence, comparable to the boiled white of an egg or cheese, whilst the gray substance is so pale as to be hardly distinguishable from the former.
The condition of the skull is, according to Rokitanski,1 as follows: In cases in which the hypertrophy of the brain has advanced to a high degree, and in which the sutures of the skull are united, the bones of the cranium are found thinner and their inner table roughened by absorption. This is especially the case in the bones which form the vault of the cranium. The holes or other deficiencies found at the base of the cranium in the plates of the frontal, ethmoid, and sphenoid bones are not entirely due to the absorbing process, but rather to the thinness of these bones. In infants the cavity of the cranium enlarges in proportion to the hypertrophy of its contents; the head then resembles in form so much that of hydrocephalus that it may lead to errors in diagnosis. In some cases in which the disease rapidly develops to a high degree there is observed on the infant's skull a loosening and separation of the sutures of the cranial vault, with red coloration and suffusion of their cartilages.
1 Lehrbuch der Pathologischen Anatomie, 3d ed., 1855, vol. ii. p. 431.
SYMPTOMS.—There is a gradually increasing muscular weakness, manifesting itself especially in the lower extremities, and giving rise to an unsteady, stumbling gait and frequent falling, caused perhaps by the excessive weight of the head, and also an inability of securely grasping objects. Besides these disturbances of motion, epileptic spasms appear, at first light in degree and at long intervals, but becoming later on in the course of the disease more frequent and severe. Continuous or intermittent attacks of headache almost always accompany the disease, and, furthermore, vertigo, tinnitus aurium, photophobia, and dimness of sight with dilatation of the pupil; general sensation also becomes blunted, but without ever amounting to anæsthesia. In a number of cases there is no disturbance of the psychical functions, though in others symptoms of mental excitement amounting even to delirium have been observed. Most frequently the intelligence sinks from the beginning of the disease, to end in complete idiocy. The pulse also has been observed to fall considerably during the last stage.
The COURSE of the disease is, according to Andral and Hasse,2 almost always chronic, and if an acute development of the affection has been spoken of, it may be supposed that the latter has commenced a considerable time previous to the manifestation of the symptoms during the last stage. Andral divides the disease into two stages, of which the first is chronic and frequently latent, whilst the other is more acute and leads to a rapid fatal termination. In most cases death is caused by such intercurrent affections as give rise to irritation and hyperæmia of the brain, and thus increase the already abnormal pressure upon this organ.
2 “Krankheiten des Nervensystems,” 2d ed., 1869, in Handbuch der Speciellen Pathologie und Therapie, edited by R. Virchow, vol. iv. 1st div., p. 578.
DIAGNOSIS, PROGNOSIS, AND TREATMENT.—It has already been mentioned that errors in diagnosis may very easily be committed on account of the great resemblance in the form of the head in cases of hypertrophy of the brain and of hydrocephalus, though it has been stated that in the former affection convulsions, in the form of epileptic spasms, predominate, to be followed during the last stage by symptoms of depression; whilst in hydrocephalus the symptoms of depression manifest themselves from the beginning of the disease, and, moreover, the rachitic deformities are more prominently shown in the form of a chicken-breast. A positive diagnosis can only be made by the autopsy.
There are no remarks to be made on the prognosis and treatment of hypertrophy of the brain.