The rapidity of the enlargement dif fers very much in different cases, and the clinical history depends largely upon this fact. In cases in which the increase of fluid is very slow the brain seems to accommodate itself to the pressure, and the symptoms of intracerebral pressure may be very few or almost entirely lack ing until the case is far advanced. When chronic hydrocephalus is secondary, and arises after ossification of the cranial bones is firmly established, the symptoms of increased cerebral tension are earlier and more markedly seen, although the amount of fluid in the ventricles is rela tively very small in comparison to the primary cases. A well-developed case of internal hydrocephalus presents quite a striking and characteristic appearance. The face is small and overshadowed by the enlarged cranium, the forehead is prominent and bulging, the eyes are directed down and formed so that the white of the eye is always more or less uncovered by the upper lids, the child is often restless, and there is frequently twitching of the extremities; a short, sharp cry is often given, and, taken in connection with the emaciated body, the picture presented is almost pathogno monic of the disease. The head is often rather flat behind, with bulging sides and greatly-rounded frontal regions.
Etiology.— Chronic hydrocephalus arises often, especially the congenital cases, without any demonstrable lesion of the brain. In many cases it is due to meningitis, or to other organic disease of the brain, such as tumor. Some au thorities attribute a large proportion of the cases to syphilis, which certainly does appear often in the family histories.
Observations made upon IS cases of hydrocephalus. Of thee. 3 had well marked symptoms or signs of congenital syphilis. Among the remaining 15, 13 V, per cent. presented signs of enlarged liver and spleen, and which the writer believes were cases of hereditary syphilis, the result of an attenuated virus. It was noted that the apparently-healthy mothers of hydrocephalic children aborted more frequently than mothers who had borne healthy children. H. Elsner (Jahrbuch. f. Kinderheilk., B. 43, II. 4).
Other authors ascribe the congenital defect to rickets, but this connection is not by any means clearly proved, for much confusion has arisen from the fact that, clinically, rickets and hydroceph alus have frequently been confounded, but they are sometimes associated. Pri mary hydrocephalus has also been caus atively referred to tuberculosis, but there is lack of positive evidence. The influ ence of heredity is probably an important factor; often two or more children in the same family have been affected.
Extreme overwork and worry in the mother is, I believe, an important factor in determining the occurrence of pri mary hydrocephalus. It must be ad mitted, however, that we are still in the dark regarding the essential causative factor of primary hydrocephalus. In some cases of secondary hydrocephalus the cause can be clearly traced to an an tecedent mild attack of basilar menin gitis, or to a basal tumor, or to some mechanical cause producing venous stasis in the vessels supplying the ventricles.
The most frequent causes of obstruc tion in eases of chronic hydrocephalus are simple fibrous closure of the foramen of Alagendie, adhesion of the surfaces of the tonsils of the eerebellmn to each other and to the margin of the fourth ventricle, and the presence of cysts be tween the arachnnid and pia, at the pos terior inferior aspect of the cerebellum. A. Bruce and IL.). Stiles (Scottish sled. and Sing. Jour.. Al Pathology.—The lesions found post mortem are caused by the enormous dila tation of the ventricular cavities in which the effusion usually accumulates. Thus in very marked cases all the walls of the ventricles are extremely thin, the septum lucidum is obliterated, and sometimes the brain-substance forms a mere envel ope for a large central cavity formed by the gradual expansion of the ventricles. In more extreme cases nearly all of the brain-substance may have disappeared through the effect of the great pressure, and the brain resembles a cystic tumor, with only the basal ganglion and cere bellum and portions of the temporo sphenoidal remaining, as in a case of Peterson's, referred to by Holt. The fluid found in cases of chronic hydro cephalus is slightly alkaline, translucent, specific gravity about 1005, and contains a trace of albumin and sometimes sugar. It also contains traces of alkaline chlo rides and phosphates. The fluid in cases arising from meningitis is usually more turbid and contains a larger percentage of albumin. The quantity of fluid varies from a few ounces, in secondary cases, to six pints or more in primary cases.
Hydrocephalic fluid is sterile and faintly alkaline and of a specific gravity varying from 1005 to 1010, having no toxic action upon animals. The propor tion of albumin remains constant (about 0.25 per cent.), despite repeated punct ures. Glucose has never been found, nor has peptone, urea, mercury, or potas sium iodide. Salts are present in small quantity. It has the same chemical coin position as physiological eerebro-spinal Iluid, and consequently is not an exudate or transudate, but a true secretion. Con cetti (Wiener kith. Woeh., No. 42, S. 034, '97).