Chapter LXIV: 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 {994} 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, {995} 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 {996} 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.