Brain

In his classificationof brain abscessesDr. Eagletonhas adopted a nomenclature which is unlikely to meet with general acceptance . According to the mode of entry of infection he uses the terms adjacent or secondary and intercurrent or tertiary. The terms used do not seem to be well chosenand do not correspondwith their more generally accepted meanings in pathological terminology. The chapterson the general diagnosisof brain abscess are well planned. The author attaches much importance to the initial vague rigor followed by a subnormal temperature and by repeatedfailure to recoverbacteria from the blood. The localization of brain abscessesis also fUlly ais· cussed. He is of opinion that these occur in situations more or less d'efinitely corresponding to the extra-cranial focus . As valuable localizing signs much importance is attached to "naming aphasia" and transient or incomplete hemianopsia, especia lly for colours in temporo-sphenoidallobe abscesses . The latter is said to be due tothe involvement of the fibres of Meyer's tract in their course from the cuneusto the pulvinar region. The importance of the presence of a capsule in brain abscessill indicated and the mechanical difficulties of draining acuteabscesses without a capsule in an adequate manner are fully dealt with. The author illustrates his encephaloscope for viewing the interior of an abscess. It is a hollow tube of similar pattern to a Kelly's speculum illuminated by a head lamp and fitted over a hollow metal searcher to be inserted into the abscess.It is not clearly disclosed in the text that by the use of the encephaloscopean acute abscess can be more effectively drained. As a record of the author's personalexperienceswith full notesot his operation cases and autopsy findings the, volume will repay careful study. The mortality of brain abs cess is still approximately 75%, but the author is of opinion that with earlier diagnosis and earlier operation his operative resultsin recentyearshave greatly improved.

We are here dealing with an involvement of the most highly specialized body tissue with destruction and subsequent damage to the body welfare. Possibly the worst feature is the fact that actual nerve tissue will not regenerate, so as a !'Jlle there must be Some residual left.
It is a relatively new subject, not from the standpoint of recognition, for it was recognized years ago, but from that of early symptoms, early diagnosis and treatment. It is still confused with meningitis, "At this time he has no pain in the heRd Rlthough he has been subject to headaches. He is a man of very temperate habits, but any occasional indulgence in stimuli would affect the brain so much as to cause a temporary insanity. His pulse is regular, tongue clean.
fl8th. Had two paroxysmal attacks yesterday and one of long duration in the evening. There is no loss of consciousness.
tt9th. Two paroxysms yesterday; these are less violent. The right arm is becoming paralytiC. A diffused dark-coloured inflammation is appearing upon the right leg.
"lOth. Patient is now hemiplegic but rational. "13th. Sensorium affected, starts suddenly when spoken to, answers questions in a sharp, petulant manner, disposed to sleep.
U15th. Lies in a state 'of stupor, pulse slow.
The sore on the leg appears gangrenous.
17th. Breathing anxious, pupils not obedient to light, laboring under symptoms of effUSion; in the brain, has remained the same for four days. Death on the 25th. "Post mortem. No fracture line noted. . On lifting the dura, large quantities of greenish coloured pus was poured out of the posterior part of cerebrum, the right hemisphere. The cerebellum appeared free from clisease". This description impresses one as being exceedingly good in describing the symptoms present. These medical men had quite a good understanding of the nervous system and its affliction. Previous to 1800 abscess was not generally recognized.
Wernicke's Lerbuche d. Gehunkiankheiten (2) in 1883 outlined a division which was ultimately to become marks of infectious and non-infectious abscesses.
During 1883 another London physician reported an abscess at post mortem and remarked to the effect that an abscess was an occurrence of once in the course of a lifetime. This report was observed in Lancet, London, May 1883. by William Macewen, a Scottish surgeon, who did not quite agree to the statement and who decided that brain abscess was far more common than sus- Korner's studies (1902 -1908)

ETIOLOGICAL SURVEY
Absc.ess of the brain is secondary to a primary focus elsewhere in the body. In general, conditions which may lead to brain abscess are direct extensions of trauma to head, infective conditions of the ear, eye, nose and its accessory sinuses, and infection of the face and scalp. Metastatic abscesses ma.y develop from endocarditis, osteomyelitiS, bronchiectasis, abscess of lung, pneumonia, empyema, streptothrix origin, puerperal infection, liver abscess and cerebro-spinal meningitis. Septic diseases of the ear are the most common causes. of brain abscess and are responsible for I 33 to 50 percent of the cases. Chronic aural diseases cause more brFin abscesses than acute conditions. Otitis -~ --6disease may extend into the brain along thrombosed vessels or lymphatics. Sequestra in the temporal bone may be regarded as exciting causes (7).
Trauma of the head is a rather frequent cause.
The basis for this is trauma to the part causing lowering of tissue resistance plus a primary focus in the body. Trauma probably plays a more important part in the production of frontal lobe abscess than abscess in any other part of the brain (1). Trauma followed by increased intracranial pressure due to edema suggests the possibility of abscess. The brain is attached to the dura by blood vessels and nerves, the dura to the bone by fibrous connective tissue. Direct or contrecoup violence may produce tearing of the vessels with hemorrhage and edema, and with this sort of pa,thology laid down plus lowered resistance, a potential abscess In a number of post mortem analyses , it htts been found tha.t an abscess primarily situated in the piarachnoid will remain localized but by pressure effect may cause brain necrosis at this area, but never resulting in actual abscess. An extension abscess or a so-called temporosphenoidal abscess with a tt stalk ft is located in the second convolution of the temporosphenoidal lobe, directly above the tegmen (11).
Another group which must be differentiated from the adjacent type already discussed are the metastatic abscesses, purely hematogenous in origin. An adjacent abscess is adjacent to the primary focus, such as extension from the middle ear into the cerebral tissue (10). An infected embolic particle circulating in the blood stream with later occlusion of the vessel with tissue death is the beginning of an abscess. A metastatic affair may be so sudden as to produce apoplectiform symptoms whereas adjacent abscesses are always slow in producing symptoms (7). Abscesses of metastatic origin from the ear are not common. Eagleton reports only one case. It is believed that about 12 per cent are due to suppurative disease elsewhere.
Two cases with primary origin of amebic dysentery of the liver have been reported.
In cerebellar abscess the larger number of them originated from aural infection. In 117 post mortems (12), 99 were of otitic origin, 2 from sphenoid sinus suppuration, 2 from metastasis, 2 traumatic and 2 tuberculous, 1 c8,rcinoma and 1 syphilis. Acute exacerbation in chronic suppuration is generally the immediate cause while trauma during mastoidectomy may also be a factor.
The accompanying chart is worked out on the principle of metastatic and direct extension forms. Histolytica.
The following Considered on a histological basis, cerebral tissue is composed of neurons, the functioning cells of the brain and the most highly specialized tissue in the body. Lying between the neurons is the supporting tissue of the brain, the neuroglia, glial cells and the fibres. The neuroglia plays an entirely inactive part in the nervous mechanism in that along with the small amount of connective tissue from the pia and alongside -12-the blood channels it forms a framework in which the nerve cells functionate.
Under pathological conditions certain cells of the neuroglia take on ameboid activity and are ins tNmental in the removal of waste products of the brain.
The more highly specialized the cell, the more it depends upon nutrition for its life, and the less able it is to regenerate itself. Nerve cells thus die easily and do not regenerate; glial tissue itself, not brain tissue proper, regenerates. This regeneration, however, plays no active part in restoration of nerve function. Thus in any pathological condition which is not relieved at an early date there is a proliferation of glial tissue which replaces the active neurologic tissue.

PATHOLOGY OF CHRONIC BRAIN ABSCESS
The pathological process in chroniC brain abscess is the same as in abscess formation in other parts of the body; that is tissue death and changes due to the tissues' protective reaction, the latter being governed by the specia,l tissue involved.
A microscopic examination of a chronic brain abscess with a capsule shows it to be composed of: (1) a varying sized cavity filled with pus and detritus, the final result of complete death of tissue from bacterial action and nutritional disturbances, (2)  The connective tissue reaction of the body is simply the attempt of the organism to limit the extent of the inflammatory process. In most parts of the body a low virulent infection is usually encapsulated by connective tissue because connective tissue is easily available, is a low order of cell and proliferates rapidly. In the brain, however, the tissue is so highly speciallized, so compact, that connective tissue formation takes a longer time; also because practically all of the new cells making up the capsule must be brought to it by the newly formed blood vessels. These The opposite may hold true in which the cerebellar abscess may be primary and not secondary to sinus thrombosis •. ·Wa1bach (13) found that with increased intracranial pressure the sinuses were obliterated and small areas of brain tissue are herniated into the yielding pOints of the entrance of the arachnoid villi within the sinuses. The herniation may be followed by occluding thrombus which may undergo septin degeneration.
Traumatic and metastatic abscess similar to cerebral abscess has already been discussed, Courville and Nielsen (28) have found that in the cases of 10,000 autopsies, 76 cases of brain abscess were found. The sources of these abscesses are given in the following  (2) Owing to multiple thrombosis of the cerebellar veins; (3) Owing to multiple pOints of invasion from a diffuse exudate about the peduncles.

PROOF OF CEREBRAL SUPPURATION
An initial vague chill indicates the beginning of an intradural suppurative process (26). Macewen (3) does not consider this factor in his early diagnosis, This mild symptom was not utilized until the 1900s.
Since that time, textbooks dealing with nose and throat Convulsions may be more frequent in the metastatic type although no meningitis may be present. Con-vulSion may occur in intradural abscess, probably expressed as cortical instability or as in a metastatic type of abscess (15).
There has never been an adequate explanation for the cause of subnormal temperature in cerebral abscess, This fact is of the greatest diagnostic importance. Our theory to explain this is that the normal temperature is disturbed because of the interference with the heRt regulatory center by cerebral sup~uration.
It is believed th8"t the brain possesses two sets of cells which cause an increase or a loss of heat according as one or the other is stimulated (16).
This idea is possibly erroneous and is not believed in by the physiologists as being the factor. Experiments have shown that the heat regulatory centers are located in the nesencephalon and that by removal of the cerebral hemisphere and the thalamus the mechanism for regulating body temperature is d.estroyed (16,17).
Other theories are those of an endocrine hookup, the brain itself possessing endocrine substance which helps to add tonus to the heat regulatory center.
There may be a distant relptionship between the brain and other endocrine centers which has some connection with the heat regulatory center (17).
In a comparison between meningitis and brain abscess we find that the meningitis temperature curve is exceedingly high, this being due to the microorganisms passing into the blood stream and the irritation to the meninges. When there is no suppuration near the meninges in abscess plus thrombosis of vessels and autolysis in the region of the abscess, the temperature findings may be accounted for (18).
Papilloedema may occur in abscess, but never with the frequency and intensity as found in brain tumor. Frontal lobe abscess may never show any degree of papilloedema but cerebellar abscess may. This is due to a disturbance in the cerebrospinal circulation (19).
The abscess, when once proven to be present, must next be loca.lized. A determination has to be mEde whether it is present in the frontal, temporo-sphenoid;:>l or the cerebellar lobes. A definite history of prime.ry suppuration is of importance, whether there has been a chronic discharging eRr, mastOid, frontal sinusitis, empyema, etc. If the labyrinth is involved, the abscess is liable to be cerebellar; if not involved, it is more apt to be temporo-sphenoidal. In ear disease as the primary focus, the absence of nystagmus and negative cold caloric test aid the early diagnosis of temporosphenoidal lobe abscess (20).
In temporo-sphenoidal abscess, two pRthogonornic signs mRy be found, aphaSia (naming) and hemianopsia. The aphasia in the early stages is apt to be transient. The trl=msverse temporal gyri contain the primary centers for the reception and analyses of the auditory stimuli (31). Pressure by abscess here may well give rise to an:~aphasia, 1. e., word deafness (21).
A hemianopSia may occur due to an involvement of the association fibers running from the cortical optical center in the cuneus to the geniculate bodies, the cuneopulvinar tract. It has been found that tumors as well as abscesses will affect this tract (22).
Facial paresis of the opposite side may be found At times. This is a cortical type of involvement.
Other signs which may be elicited are ( Barany (24) believes that the cortex of the cerebellum contains areas, the destruction of which c~uses alterations in the ability to execute certain voluntary movements properly.
The yawning may be due to disturbance of reflex.
Loss of weight may be due to disturbance in metabolism.
Loss of knee jerks would not hold true unless pyramidal tract involvement was present. According to Eagleton, The inflammatory process appeared to be localized to cerebral fossae.
Case IX. B. S.

Autopsy:
A -30 -38 Centrally located abscess in right temporal 10be~ Case X. S. V. Age 45 Autopsy: A -31 -115 Removing the dura, the leptomeninges were congested. Right temporal region was greatly softened. Central abscess found in right temporal region.

Autopsy:
A - 29 -40 The meninges showed marked inflammation with purulent exudate scattered throughout. Section of brain showed large frontal lobe abscess.
Diagnosis: brain abscess and meningitis. These have all been very interesting cases and should have been gone into more thoroughly but space would not permit.
-39-CONCLUSIONS Brain abscesses show a wide variation as to location, but some abscess areas are far more common than others. The temporo-sphenoidal lobe is the most commonly affected, due of course to the relation to the ear. This abscess may be more readily recognized thA.n those of other locations.
The symptom; complex of brain abscess is difficult to interpret. No case seems to be absolutely typical of textbook symptoms and it seems that the experienced eye with inherent good judgment is responsible for diagnosis. These abscesses seem to simulate other intracranial complications so readily thllt diagnosis just can not be made, In the future earlier signs and symptoms may be discovered which will aid in a differential diagnosis. Spinal puncture, blood counts, and temperature taking have been tremendous new aids in. diagnosis.
Treatment has not been discussed here. It is a huge subject in itself, entirely a surgical meesure with the outcome, as yet, far from perfection.
The exciting organism has not been discussed but well known are the members of the pus-forming groups. A few cases present an unusua,l organism as the exciting agent.
The cases selected from the University Hospital