INFECTIOUS DISEASES AND THE BRAIN

INFECTIOUS DISEASES AND THE BRAIN

799 THE LANCET LONDON :SATURDAY, .APRIL 14, 1934 INFECTIOUS DISEASES AND THE BRAIN IT sometimes happens in science, and especially in medical scienc...

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799

THE LANCET LONDON :SATURDAY, .APRIL 14, 1934

INFECTIOUS DISEASES AND THE BRAIN IT sometimes happens in science, and especially in medical science, that what has been regarded as an

axiom turns out to have been

a

hasty generalisa-

tion. For example, it has long been assumed that the symptoms characteristic of all feverssuch as apathy, insomnia, raised temperature, metabolic disturbances, vasomotor collapse, and eventually death-are due to disturbances of the brain centres produced directly by bacterial toxins. Prof. FRIEDEMANN and Dr. ELKELES, in the paper concluded in our present issue, throw doubt on the validity of this assumption. Whether bacteria] toxins do or do not act on the nerve-cells of the brain must obviously depend in the first place on whether they are able to reach these cells, although other factors such as chemical affinity will play a secondary part. The problem is bound up, therefore, with the problem of the exchange of substances between blood and brain. The work of the last few years has shown that this exchange is regulated by a selective mechanism, described by continental writers as the " barriere "

"

hemato-encephalique or Bluthirnschranke," or in English as the " blood-brain barrier," or B.B.B. In the brain, as in other organs, the selective mechanism is localised in the walls of the capillaries ; in this case it is in the cerebral capillaries, and not, as was formerly thought, in the choroid plexus and the meningeal vessels. FBIBDBMANN and ELKELES have devised new methods of testing the permeability of this barrier for various toxins, and their results show clearly that the toxins differ among themselves in the facility with which they pass through it. Those of the botulinus, diphtheria, and tetanus organisms, for instance, do not pass the blood-brain barrier at all (tetanus is, of course, exceptional in reaching the brain by another route, through the peripheral nerves). On the other hand, there are some, such as lamb-dysentery toxins and cobra venom, which definitely do go through the barrier. The two groups differ also in another respect : those that are able to pass the B.B.B. produce their lethal effect rapidly, whereas those that cannot pass the B.B.B. require a period of incubation. If this tentative generalisation should be found to hold good for all toxins, it will mean that few bacterial toxins act on the brain ; for we know that most of them require a period of incubation. On further inquiry into the property of the toxins which govern their ability to pass the blood-brain barrier, it was found that those that could not pass the barrier carry a negative charge, while those that could pass it are either neutral or positively charged. It follows from this that differences in the length of the incubation

period characteristic of different toxins depend on their electrical charge. The subject is highly technical and may at first sight seem somewhat remote from practice. Prof. FRIEDEMANN, however,

is not

only

a

laboratory

worker but also a clinical authority on the treatment of infectious diseases, and his investigation has clearly arisen as an attempt to account for the clinical features of these diseases and also for failures in their treatment. The handling of diphtheria, for example, is to some extent based on the assumption that the toxin has a direct localised action on the brain and also on the heart muscle, and FniBDEMANN’s treatment of it has been profoundly influenced by the results of his laboratory studies. Since vasomotor collapse, which is an outstanding feature of diphtheria, has been ascribed in the past to a paralysis of the vasomotor centre, it has been treated by drugs expected to stimulate the centre ; though FRIEDEMANN says he has never seen any good come from such remedies. But if diphtheria toxin does not reach the brain, the vasomotor collapse must be of peripheral origin and must be treated accordingly. With this in view he instituted in Berlin its management by means of hot baths, and he claims that " the effects of this treatment are striking even in the most severe cases, and not to be compared with those of drugs. Symptoms are improved at once and remain so for hours." According to his new conception of the pathogenesis of infectious diseases the toxins of many other infections should produce their effects peripherally and not centrally, and it may be expected that a better understanding of their action will lead to further improve ment in their treatment. The Medical Research Council is to be congratulated on having enabled Prof. FsiEDEMANN to continue his work by providing him with laboratory facilities in

London; A GENERAL MEDICAL SERVICE THE official report of the annual meeting in Llandudno last September of the National Conference of Friendly Societies contains a scheme for a general medical service submitted by its executive committee. The services proposed were compre-

hensive, covering treatment by a family doctor, medicines, nursing in the home, provision of consultants, specialists and auxiliary means of diagnosis (presumably pathological) through the general practitioner, home hospitals in which general practitioners would treat their own patients and meet one another in friendly consultation, residential accommodation in hospitals, sanatoria, and convalescent homes, and such other medical and allied services as may from time to time be arranged. In addition to insured persons as defined in the National Health Insurance Acts, persons who would be insured but for the fact that they are following excepted employments would become compulsory contributors, and voluntary participation would be extended to all members of friendly societies. Further, dependants of all such persons would be brought into the scheme and an arrange-