AN EXPERIMENTAL AND CLINICAL STUDY OF INTERNAL HYDROCEPHALUS
Journal of the American Medical Association (JAMA)
Numerous methods have been suggested for the treatment of internal hydrocephalus, none of which have been productive of satisfactory results. So long as the etiology of this condition remains obscure, the treatment must necessarily be only symptomatic. In the hope of clarifying its etiology and thus affording a rational working basis for its relief, we have undertaken this investigation. The present communication, which is presented as a preliminary report, includes observations on dogs after
... ons on dogs after the production of experimental hydrocephalus, together with observations on patients suffering from the disease. We have also considered the manner and the place of formation and of absorption of the normal cerebrospinal fluid and the relation of these factors in the production of this pathologic condition. HYDROCEPHALUS EXPERIMENTALLY PRODUCED From a survey of the literature we have been unable to find any record of hydrocephalus having been produced experimentally. In our experiments an obstruction has been placed in the aqueduct of Sylvius, and thus the only way of exit for the cerebrospinal fluid from the third and the lateral ventricles has been occluded. An internal hydrocephaius has invariably resulted. . The following is the procedure: A bilateral suboccipital decompression is made through an occipital midline incision. After exposure of the cerebellum it is retracted upward, and the foramen of Magendie' carefully enlarged by incising the .membrane joining the cerebellum and medulla. A piece of cotton in a small gelatin capsule, placed on the end of a gradu-. aled carrier, is inserted through this enlarged foramen of Magendie and gently passed along the floor.of the fourth ventricle into the aqueduct of Sylvius, where it is deposited by withdrawal of the carrier. The symptoms which are observed following the operation are principally lethargy and vomiting (general pressure symptoms) dating from the time of operation. When carefully performed there are no irritative or destructive symptoms from the operation. This hydrocephalus therefore is due to a purely mechanical obstruction in the aqueduct, as there is no interference with the veins of Galen. Since the venous obstruction is considered a possible cause of hydrocephalus, a scries of experiments was conducted in which the vein of Galen and the straight sinus were ligated. In none of these cases did hydrocephalus result. ABSORPTION OP THE CETÍERROSPINAL FLUID There are many theories concerning the place and manner of the absorption of cerebrospinal lluid. In the study of absorption in the experimental and clinical work we have used almost exclusively phenolsulphonepbthalein. This inert colored solution, first introduced into practical medicine as a renal test by Rowntrce and Geraghty, has since been shown to be an accurate index of fluid absorption when the renal function is normal. It is very stable, is excreted in the urine with groat * From the Departments of Surgery and Pediatrics of the Johns Hopkins University. rapidity, is easily detected in minute traces and is readily adapted to' accurate quantitative estimation.1 Since an internal hydrocephalus can be experimentally produced by occluding the aqueduct of Sylvius, it. is evi-Vlent that absorption of fluid from the ventricles is less rapid than its production. In the studies of the absorption from the ventricles of patients with an internal hydrocephalus due to obstruction in the aqueduct, after the introduction of phenolsulphonephthalein in the lateral ventricles, there is excreted in the urine from. 0.35 to 1 per cent, during a period of two hours; but when it is injected into the sttbarachnoid space of the same patient there is an excretion of from 35 to CO per cent, in the urine in the same period of time. This demonstrates that the absorption of cerebrospinal fluid takes place almost entirely in the subarachnoid space. It is evident that the fluid must be absorbed, either into the blood or lymph-vessels. When phenolsulphonephllialein or other inert colored solutions are injected into the subarachnoid space, they appear in Ihe lymph of the thoracic and right lymphatic ducts only after an interval.of from thirty to fifty minutes, and only a faint trace is present even after two hours, whereas, they appear in the blood in three minutes and in the urine in six minutes and, as mentioned above, from '! "> to GO per cent, is excreted in the urine at the end of two hours. These fads indicate that the cerebrospinal (luid passes directly into the blood and that tbe lymph-vessels are not concerned in its absorption. There are three principal views regarding the manner in which the cerebrospinal fluid passes into the blood: (1) by means of stomata arranged along the venous sinuses; (2) through the pacchionian granulations, and (3) by a general process of osmosis. When a suspension of fine granules is injected into the subarachnoid space the granules tîo not' pass into the blood except in very minute quantities and after a long interval of time. Consequently the assumption of special openings (stomata) from the subarachnoid space into the venous sinuses seems unlikely. This applies to granules injected into the subarachnoid space under normal conditions of pressure. If pressure is used, especially on young tissues, foreign materials can easily be forced into the veins. In adult animals this requires a very high pressure. It should be noted that stomata were formerly believed to exist in the peritoneum to explain the absorption from this cavity, but this has been shown not to be the case. That the pacchionian granulations do not plav any special rôle in absorption can, we think, also be shown. These granulations arc absent in many species of animals, are always variable in number and size and develop principally in adult life. After fine granules are injected'into the subarachnoid space, local collections are deposited along the sinuses especially Ihe superior long i tnilinal sinus-in the interstices of the fibrous meshwork which forms the walls of the sinuses. These deposits are in all essentials similar to those in the pacchionian granulations. There is always a layer of dura and arachnoid separating these masses of granules from the blood in the veins. This is a much greater mechanical barrier to absorption than is present in the exposed capillaries of the pia-arachnoid. After the injection of phenolsulphonephthalein into the spinal subarachnoid space (the communication with 1. It should be emphasized, however, that ordinary solutions of phenolsulphonephthalein are made up in alkali, which is sufficient to militate against its use in the central nervous system. To overcome this defect we use a neutral solution specially prepared for us by Hynson, Westcott & Co.