BY FRANCIS MINOT, M.D.
SYNONYMS.—Dropsy of the brain, Dropsy of the head.
DEFINITION.—A gradual accumulation of serous fluid in the brain, occupying either the ventricles or the cavity of the arachnoid, or both, occurring chiefly in infants or very young children.
The term hydrocephalus, which was applied by the older writers to accumulations of serous fluid both within and also without the cranium, termed distinctively internal and external hydrocephalus, is now restricted to dropsical effusions either between the meninges or within the ventricular cavities. These may be acute or chronic, and they arise from the same conditions which are followed by the effusion of serum in other parts of the body; that is to say, from an alteration in the serous membrane lining a cavity, from an obstruction in the capillary circulation with increased tension in the larger vessels, from an altered condition of the blood, etc.
Chronic hydrocephalus is almost entirely confined to young children, and is probably due to an arrested development of the brain, as shown by its being usually congenital, by the dwarfed intellectual condition of the patient, and by its frequent association with spina bifida. The pathogeny of the disease is, however, still obscure. Whether the abnormal accumulation of serous fluid is to be ascribed to a chronic alteration of the ventricular walls or of the choroid plexuses, allied to inflammation, such as occurs in the pleura, for example, causing an increased secretion, or to a closure of the communication between the ventricles and the spinal cavity, as suggested by the late John Hilton, resulting in dropsy by retention, or to some other cause, is not yet determined. Hilton says:1 “In almost every case of internal hydrocephalus which I have examined after death I found that this cerebro-spinal opening [between the fourth ventricle and the spinal canal] was so completely closed that no cerebro-spinal fluid could escape from the interior of the brain; and, as the fluid was being constantly secreted, it necessarily accumulated there, and the occlusion formed, to my mind, the essential pathological element of internal hydrocephalus.” Sieveking, commenting upon Hilton's theory, says:2 “While giving these facts due weight, it must be pointed out that we are yet far from understanding either how the fluid is poured into the cerebral cavities or how it is removed, and that we do not positively know that the spinal canal has any better means of getting rid of an excess of fluid than the cerebral cavities have.” An arrest of the growth of the brain is supposed by some pathologists to account for ventricular as well as arachnoidal dropsy by the creation of a vacuum in the cavity of the cranium, which is filled by exudation of the more fluid portion of the blood from the vessels or of lymph from the lymphatics.
1 John Hilton, Lectures on Rest and Pain, etc., 2d ed., New York, 1879, p. 22.
2 Jones and Sieveking's Pathological Anatomy, 2d ed., London, 1875, p. 248.
ETIOLOGY.—That chronic hydrocephalus in young children is in a large proportion of cases an hereditary disease is shown by the fact that it is frequently congenital, that more than one child in a family is occasionally affected by it, and that while one child is hydrocephalic others may be idiotic. A scrofulous taint in the family history is noticeable in many cases, the evil effect of which is frequently enhanced by unfavorable sanitary conditions of life, especially by residence in dark, damp, ill-ventilated, and badly-drained apartments and by insufficient or unwholesome food. Hence the disease is more frequently met with among the poor than in the well-to-do classes of society. There is a difference of opinion as to whether it ever arises in consequence of external violence, such as a blow on the head, or of some strong impression, like fright or grief, acting on the mother of the child during pregnancy. The probability is that such causes would not be efficient except in cases where a predisposition to hydrocephalus had already existed. West3 mentions the case of a healthy child five months old who fell out of the arms of her nurse, and was taken with a fit the same day. She apparently recovered, but when a year old had frequent returns of convulsions. At the age of fifteen months the head began to enlarge, and it continued to increase in size until she was three years old, when she was attacked by measles, and died in a few days with convulsions and coma. The symptoms, both bodily and mental, were typical of hydrocephalus, and the diagnosis was fully confirmed by the autopsy.
3 Op. cit., p. 127.