TUBERCULOUS MENINGITIS Tuberculous meningitis is invariably caused by Koch's tubercle bacillus.
The insignificant pyogenic faculty of the tubercle bacillus is recog nized; hence the probability of a mixed infection is suggested whenever, as not infrequently occurs, considerable pus is encountered in a case of tuberculous rneningitis. Mixed infection may be caused by a number of microorganisms, most frequently the meningococcus and the pneu mococeus. It apparently does not have much influence on the course of the disease; its effect on the pathologic process and especially the cellular constituents of the cerebrospinal fluid is greater.
While clinically, tuberculous meningitis often produces the impres sion of an absolutely independent disease, since it attacks children who have hitherto been healthy, nevertheless it must be maintained that it is always a secondary disease.
The primary tuberculous focus may be situated in the immediate vicinity of the meninges, in the nasal cavity ;Demme), in the bones of the spine or skull, in the middle ear and in the mastoid cells. The tubercle bacillus forces its way- along the lymph channels to the meninges, and if the conditions are favorable remains there and multiplies. Occa sionally also the bacillus can reach the cerebrospinal canal by way of the lymphatic investments of the nerves, a mode of infection to which Striimpell and Leube particularly have directed attention.
As a rule infection by extension appears to be of much rarer occur rence than by metastasis through the circulation of the blood.
An argument in favor of this is the arrangement of miliary tubercles along the vessels of the pia mater, sometimes in such a manner that the terminal expansions of only a single branch or of 60MC rather diminu tive branches are attacked. The primary foci, corresponding to the prevailing character of tuberculosis in childhood, are situated chiefly in the lymph-nodes. Of these the cervical and submaxillary nodes, which receive the lymph from the mouth and pharnyx, and especially the bronchial and mediastinal nodes are probably the most frequent sources of infection, indirectly however by way of the blood vessels.
The breach through which the tuberculous virus enters the circulation is by no means always discoverable in the cadaver; but it has been found so often (by Huguenin before Weigert's work hacl directed atten tion to this point, and later by others) that this method of infection is positively established.
Besides the lymph-nodes, of course pulmonary or osseous or uro genital tuberculosis can furnish the primary focus. Almost always miliary tuberculosis of the liver, spleen, etc. (often however so slightly developed as to preclude clinical diagnosis) is found at the autopsy. Just as miliary tuberculosis in other non-nervous organs in cases of meningitis is almost invariably found, so there are, on the other hand, numerous cases in which, notwithstanding widely disseminated miliary tuberculosis of the entire organism, the pia mater has remained intact. This fact presents one of the most interesting problems of the patho genesis of meningitis.
The dissemination of tuberculosis in the body proceeds so irregu larly that it is impossible to await or predict its seizure upon the meninges at a definite stage. For this reason, search for an exciting cause for this event is the more justifiable—even if we do not reach a positive result.
Etiology.—Here WC may place in the front rank the infectious fevers, especially measles and whooping-cough. They, like all exciting causec, act by stimulating a localized, 1110IT or less dormant tuberculous process. But in regard to whooping-cough it must be observed that it is often a question whether the spasmodic coughing spells have not indeed been the expression of advanced tuberculosis of the bronchial glands. It appears more certain that measles may incite a hitherto latent glandular tuberculosis to a more rapid miliary dissemination which may involve the meninges.