By more or less abundant admixture of cells the exudate, which in a pure state is clear, is often tinged gray or yellowish green, at times even resembling pus. The bands of exudate enveloping the vessels often extend from the base to the convexity, and the sheaths of the cranial nerves also appear already macroscopically infiltrated.
We shall return later to the cellular elements of the exudate and cerebrospinal fluid, which are important in relation to clinical diagnosis.
A6 evidence of the participation of the cerebral ventricles in the inflammatory process we find granular ependymitis (apparently pos sessing no physiologic significance), the chorioid plexus infected with miliary tubercles and exudate, and—most important—internal hydro cephalus.
Its development may show decidedly different degrees if we take as a criterion, on the one hand flattening of the cerebral convolutions, on tbe other, size of the ventricular cavities. While cotnpression phe nomena, like the symptoms of cerebral pressure, never fail to appear in tuberculous meningitis, the hydrocephalus may in one case be slight, in another case so considerable as to justify the suspicion that an abnor mally large ventricular system already existed previous to the meningitis.
The sig,nificance of this symptomless stationary internal hydro cephalus, since it is so frequently combined with tuberculous meningitis, would probably be that it represents the cause of or indicates a patho logical condition of the central nervous system which facilitates the infection.* A critical study of the circulatory and nutritive relations of the central organs might afford a deeidedly interesting explanation of this complicated matter.
Clinical Discussion of Tuberculous Meningilis.—Tuberculcals menin gitis, as we have already stated, presents a secondary localization of the tuberculous infection. The few observations in which the primary focus could not be discovered do not invalidate this fact. As will be shown later, however, the clinical manifestations of the disease are often influenced by the association with advanced tuberculosis of other organs. It is iinportant to consider the relationship of tuberculous meningitis to other tuberculous diseases. The available statistics (Brandenburg, IIaushalter and Fruhinsholz, and others) based upon post-mortem material, supply no perfectly satisfactory picture, and we accordingly refrain from discussing them. Our own clinical experience allows us to state thc following:— In the course of widespread pulmonary tuberculosis in children we observed tuberculous meningitis supervene just as infrequently as is the rule in adults, even if, as often happens, a recent miliary tuberculosis which had caused no independent clinical symptoms was found at the autopsy.
Tuberculosis of the peritoneum, abdomen, genitalia or bones, leads to meningitis almost as infrequently, except indirectly through miliary processes widely distributed and clinically plainly recognizable. The experience, repeatedly corroborated in the literature, that meningitis very often succeeds operative interference with tuberculous lymph nodes, joints, or bones, agrees with this observation. IIere the exciting of a quiescent focus leads to numerous metastases, which involve also the meninges, exactly as occurs in other cases through the agency of acute fevers, traumatism, etc.
The younger the meningitis patients are, the more frequently are cases met with in which there was suspicion of latent tuberculosis before the appearance of the prodromal symptoms. These children may be attacked by the disease while in perfect health, indeed many of them appear exceptionally' robust. Henoch's dictum that tuberculous men ingitis is a terminal localization of tuberculosis should not lead to the error of awaiting meningitis only in severely tuberculous individuals.
The diagnosis of tuberculous meningitis, like that of all internal tuberculous infections, is facilitated by the knowledge of a hereditary taint. Tuberculosis of brothers and sisters or the statement that a parent belongs to a tuberculous family and has shown positive or proba ble symptonis of this disease is often of decided significance. 11-e can literally subscribe to the statement of Lederer: "Tuberculous meningitis is often a subtle reagent upon a tuberculous taint in a parent, like hereditary syphilis upon a former syphilis in an ancestor. In both cases a descendant betrays thc hitherto concealed history. There are certain families in which one or both parents when young positively had even advanced tuberculosis, and in whom the proces.s was cured or arrested, so that afterwards they became so robust and vigorous as to surprise former acquaintances. Not these qualities are transmitted to their offspring, but the predisposition to tuberculosis with its manifestations in childhood." It is our impression (which it is difficult to prove statistically) that those parents with reported former tuberculosis or with a latent tuber culosis more frequently lose one of their children through tuberculous meningitis; while tuberculosis of a child of parents afflicted with florid plithisis appears in the majority of cases as pulmonary tuberculosis also, and terminates fatally without meningeal sequelte. Perhaps the magni tude of the infection is the decisive feature in these cases.