Chapter VIII (1)

THE INFECTIVE DISEASES OF THE BRAIN AND MENINGES: ABSCESS OF THE BRAIN, MENINGITIS, LATERAL AND CAVERNOUS SINUS THROMBOSIS, HERNIA CEREBRI

ABSCESS OF THE BRAIN

Abscess of the brain may be considered under the following headings:--

Multiple abscess.

Acute traumatic abscess.

Chronic abscess.

=Multiple abscess.= Multiple abscess results from the lodgement of infected emboli which, derived from an acute infective osteomyelitis, endocarditis, gangrene of the lung, &c., are carried by the blood-stream to the brain. Multiple abscess of the brain may therefore be considered as part of a general infection. On account of the symptoms dependent on the primary infection and on the secondary pyæmic developments, a diagnosis can seldom be determined, and, even in those rather hypothetical cases in which suspicion may be aroused, surgical interference is quite useless and the prognosis hopeless. It is, therefore, quite unnecessary to discuss the matter further.

=Acute traumatic abscess.= Acute traumatic abscess of the brain most commonly arises in connexion with an infected compound fracture of the skull. In the event of laceration of the dura mater, infective organisms have a ready means of access both to the meninges and to the brain itself, meningitis or cerebritis resulting. This liability to meningeal and brain infection is increased when hair, portions of clothing, bullets, or other foreign bodies are embedded amongst the comminuted fragments of bone, or driven into the brain substance. In the event of the dura mater remaining intact, meningitis or cerebritis may still develop if, as the result of scalp suppuration, the diploic vessels become thrombosed and plugged with bacteria, some of which may be carried inwards by the reversed blood-stream, and perhaps by lymphatic connexions.

The infection may remain localized to the adjacent brain substance, an acute traumatic cerebral abscess resulting, or may become more widely diffused--diffuse cerebritis--a condition usually associated with general meningeal infection.

An acute traumatic cerebral abscess is almost necessarily situated immediately beneath the site of osseous and membranous lesion, being, in fact, more a meningo-cortical abscess than a brain abscess proper. The boundaries are but ill-defined, the walls ragged, and the contents of a brown-red colour. The surrounding brain is in a condition of red softening, that is to say, extensively infiltrated with leucocytes, the vessels thrombosed and teeming with bacteria, whilst minute extravasations of blood lead to the characteristic colour both of the contents of the abscess and of the surrounding tissue.

In the more chronic cases, the surrounding area shows some attempt at repair, dense armies of leucocytes barring the way to the spread of the infection, and, in the more favourable cases, allowing of the formation of a definite fibrous barrier.

=Symptomatology.= The symptoms resulting from an acute traumatic cerebral abscess are largely dependent on the site of the abscess. In the earlier stages of development suspicion may be aroused by the presence of persistent headache--frequently localized to the region primarily affected--by mental and bodily irritability, restlessness, and pyrexia. All these symptoms may, however, be produced by the unhealthy condition of the scalp-wound--free suppuration, bare bone, and extra-dural suppuration.

On or about the third day, the condition of the patient becomes more grave, the change for the worse being usually of rapid development, and preceded by severe rigors and general convulsions. The patient shows further signs of mental irritation, being delirious, restless, and occasionally actually maniacal.

The temperature is high and rigors are frequent. The pulse is small and rapid, the respiration increased in frequency, irregular, and often partaking of the Cheyne-Stokes type. The face is livid, the skin hot and burning. Vaso-motor disturbance is evidenced by profuse sweating and well-marked _tache cérébrale_.

=Prognosis and treatment.= The prognosis is almost hopeless unless radical measures are adopted in the early stages. The scalp-wound should be enlarged and comminuted fragments of bone removed, or the skull trephined over the region of the suspected abscess. The lacerated dura mater is freely opened up and the surface of the brain exposed. Purulent material is gently removed, and the wound closed in such a manner as to allow of free drainage.

Even under the most favourable local conditions the prognosis is bad.

=Chronic abscess.= As a preliminary statement it must be pointed out that breaking down new growths, softening gummata, caseating tuberculous masses, actinomycotic and hydatid cysts, are regarded in the light of tumour formation and are discussed elsewhere.

Of 52 cases of brain abscess admitted of recent years into St. Bartholomew’s Hospital, 41 partook of the chronic type, 30 being dependent on otitic disease, 3 on frontal sinus suppuration, 5 resulting from lung disease, and 2 of uncertain origin. The 11 acute cases were either traumatic or pyæmic.

From these and other statistics it may be regarded as generally accepted that the majority of brain abscesses are secondary to chronic disease of neighbouring bone, and more especially middle ear disease. This being the case, it might naturally be inferred--on anatomical grounds--that the temporo-sphenoidal lobe of the cerebrum and the cerebellum are more liable to infection than any other part of the brain. From 100 cases treated at my hospital the temporo-sphenoidal lobe and cerebellum were involved in the proportion of about 2 to 1. Körner,[52] reporting on another 100 cases, gives the following data:--

Abscess of the cerebrum 62 cases
„ „ cerebellum 32 „
„ in both situations 6 „

Hunter Tod,[53] reporting on 100 cases treated at the London Hospital, found that in children under 10 years of age temporo-sphenoidal abscess occurred in 87 per cent. cases, and cerebellar in 13 per cent., whereas in adults cerebral abscess occurred in 65 per cent. and cerebellar in 35 per cent. The development of temporo-sphenoidal and cerebellar abscesses in the same case was observed in 5 per cent. cases.

=Pathology.= Insomuch as chronic middle ear disease forms the main predisposing factor in the development of abscess of the brain, the pathology of brain abscess in general may be considered by discussing the main features peculiar to otitic abscess in particular.

As the result of chronic middle ear disease, the mucous lining of the middle ear and its accessory cavities becomes destroyed, the antrum filled with cholesteatomata, and the middle and external ears with granulations. The discharge of pus, previously free, is obstructed, partial or complete blockage occurring. The destruction of the mucous lining allows of invasion of the surrounding bone, the veins become thrombosed and filled with bacteria, and the cancellous spaces blocked with granulations. Further erosion of the bone results, both in the upward direction towards the tegmen tympani and in the backward towards the lateral sinus groove and cerebellum. The veins of the tegmen communicate freely with those of the temporo-sphenoidal lobe, whilst those ramifying in the mastoid region either communicate with the lateral sinus itself or with the anterior cerebellar venous system. Infection may therefore spread (1) _upwards_ to the temporo-sphenoidal lobe, or (2) _backwards_ to the lateral sinus and cerebellum. In the former case, meningitis or temporo-sphenoidal abscess develops: in the latter instance, meningitis, lateral sinus thrombosis, or cerebellar abscess.

For the formation of a brain abscess it is, of course, essential that the brain membranes overlying the main site of osseous erosion should be sealed off in such a manner as to prevent a general infection of the meningeal region, the dura becoming adherent to the eroded tegmen, &c. It is œdematous and throws out granulations, both on its parietal and visceral aspects. The parietal granulations aid in the further erosion of the bone, whilst the visceral may, according to Macewen,[54] even indent the brain. By means of thrombosed veins, perivascular lymphatics, and minute arterioles, a channel of infection is now opened up between the site of osseous erosion and the temporo-sphenoidal and cerebellar lobes.

In any case the abscess usually develops in the white substance of the brain, just beneath the grey matter, and in close relation to the primary source of infection.

_The wall of the abscess._ In an abscess of rapid development the walls are ragged and but ill-defined from the surrounding brain substance. In the more chronic cases the cavity is shut off from the brain by a capsule of varying density--usually not more than one-sixteenth of an inch in thickness, but occasionally of much greater development (see Fig. 86A). Sometimes--more especially in cerebellar cases--two cavities may be superimposed, the two abscesses communicating with one another by means of a narrow, and often tortuous, channel. Successful drainage of the one cavity may be inadequate to drain its companion. This two-saced abscess will be again alluded to at a later period.

_Contents of the abscess._ The pus is usually of a greenish hue, odourless, and acid in reaction. Though often sterile the following bacteria may be cultivated--_staphylococcus pyogenes aureus_ and _albus_, _pneumococcus_, _bacillus pyocyaneus_, and the _streptococcus pyogenes_. The pus is usually of such viscidity that it cannot be evacuated through the lumen of an ordinary aspirating needle.

_The size of the abscess._ In size the abscess varies greatly, seldom, however, containing more than 5 or 6 drachms of pus.

_The neck of the abscess._ It was first pointed out by Ballance[55] that most brain abscesses secondary to disease of the bones of the skull are ‘mushroom-shaped’, the narrow portion or stem being attached to the dura mater at the original site of infection. The stalked form of abscess is ‘quite comparable, as to its mode of formation, to the superficial cervical abscess connected by a narrow track to a focus of disease beneath the deep fascia’.

_Course pursued by an untreated brain abscess._ The abscess enlarges at the expense of the surrounding tissues, either bursting into the ventricles of the brain or coming to the surface, there rupturing and leading to a diffuse meningeal infection. Some few cases have been reported in which the abscess has established a more or less efficient natural means of drainage, either along the ‘stalk’ of the abscess or by means of a new channel to the exterior. In one or two cases, spontaneous recovery has apparently taken place.

_Mode of healing after successful operation._ Previous to successful evacuation, the brain immediately surrounding the abscess cavity is compressed and anæmic. As soon as drainage is supplied, it swells out like a sponge, more or less obliterating the cavity. The closure of a cavity by means of the formation of granulation tissue probably never occurs, and, if the falling together of the surrounding brain is insufficient to obliterate the cavity, final closure is completed by the in-dragging of the overlying tissues--scalp, membranes, and brain becoming intimately fused together.

=Symptomatology.= The symptoms must be considered under the following headings:--

The symptoms peculiar to the INITIAL stage of the abscess
„ „ „ „ LATENT „ „ „
„ „ „ „ MANIFEST „ „ „
„ „ „ „ TERMINAL „ „ „

=The INITIAL stage.= If a patient suffering from brain abscess is capable of answering questions, it will usually be found that he dates his illness from some particular day when he was sick, experienced a shivering attack, or suffered from a severe attack of headache. Further inquiry, however, will almost always elucidate the fact that, for some days or weeks previously, he was not feeling well, suffering from insomnia and loss of appetite, and experiencing occasional attacks of headache. Friends and relatives may volunteer information as to general irritability, alteration of manner, incapability of mental concentration, and worry over family and financial matters.

At this stage the headache is commonly referred to the frontal region, less frequently localized to the region of the brain involved. The patient sleeps badly, and there is often a slight rise of temperature towards the evening. Occasionally he may vomit, independently of the ingestion of food.

=The LATENT stage.= Mental depression becomes more marked, headache is more persistent and now shows a definite tendency to localization, food is distasteful, and bodily wasting becomes evident. The evening rise of temperature becomes more constant, sickness more frequent, and vertigo and giddiness may be noticeable features.

=The MANIFEST stage.= The symptoms arising during the manifest stage must be considered as follows:--

(_a_) Symptoms dependent on the general increase in the intracranial pressure.

(_b_) Symptoms dependent on the localization of the abscess.

_Symptoms pointing to a general increase of intracranial pressure_

=General mental condition.= In the latent and early manifest stages the patient will answer questions more or less correctly, but with hesitation--as if from delayed comprehension and from prolongation of the latent period. Answers are often inappropriate to the question, and given with some confusion of mind and thought--the state of ‘slow-cerebration’.

The patient either lies listless and apathetic--mentally dulled--or exhibits general irritability, lying curled up in bed, intolerant of all interrogation and examination. More rarely, cerebral irritation progresses to actual mania, the patient tossing about in bed, muttering and delirious. Forcible restraint is often required. In the later manifest stages the patient lies comatose.

=Headache.= Headache is an almost constant feature, varying greatly in intensity, but often so severe that the patient is incapacitated from all attempts at conversation and movement. Exacerbations are frequent, the sufferer crying out in his agony. The pain may be localized or diffuse. Localization of the pain to some special region is of considerable aid to the regional diagnosis of the abscess--more especially so when it is accentuated by palpation and percussion over the suspected region.

=Vomiting.= Vomiting is another frequent symptom, probably dependent on stimulation of the medullary vomiting centre. It is of the so-called ‘cerebral’ type, bearing no relation to the ingestion of food and unaccompanied by previous nausea and retching. The vomited material is propelled outwards with considerable force. There appears to be some relation between the exacerbations of headache and the time at which vomiting occurs. Vomiting is most constantly observed when the abscess is subtentorial in position.

=Optic neuritis.= It is exceedingly difficult to determine the frequency with which optic neuritis develops in cases of brain abscess. Much depends on the site of the abscess and the duration of its existence. Optic neuritis is seldom absent in the more chronic cases and is most constant when the purulent collection is subtentorial in position. The non-appearance of optic neuritis--even in chronic cases--does not confute a diagnosis of abscess formation.

When once present, the swelling of the disk may increase rapidly. In a case of cerebellar abscess recently under my care the swelling reached 6D. in three days. Whatever the localizing value of unilateral neuritis in tumour formation (see p. 216), I am strongly of opinion that in the cases under discussion, optic neuritis, when confined to or more marked on the one side, implies that the abscess is situated on that side.

=The pulse and temperature.= It is commonly stated that, in typical cases of brain abscess, the pulse-rate is slowed--40 to 60 per minute--and that the temperature is subnormal. Slowing of the pulse results from stimulation of the medullary centre, the lowering of temperature to less determinate causes. In the consideration of pulse and temperature--and the two must invariably be considered together--it will, however, frequently be found that the temperature is raised and the pulse-rate but little altered. Thus, in one case the pulse was 88 and the temperature 103·4 degrees, in another the pulse was 74 and the temperature 102, in a third case the pulse was 89 and the temperature 102·8 degrees. These cases are very significant, and show that the greatest attention should be paid to a comparison between pulse-rate and temperature, a _relative_ slowing of the pulse being more constant than an actual retardation.

The elevation of temperature results from the fact that the great majority of cases of brain abscess are secondary to some highly infective purulent collection, as, for instance, a mastoid empyema. In such a case, if the mastoid region be cleared out, the temperature will fall and the typical clinical picture of subnormal temperature and slowed pulse-rate will be depicted.

=The respiration.= The increase of intracranial pressure may lead to some slowing and deepening of respiration. Irregularity is, however, the more common condition, deepening, in the later stages, to definite Cheyne-Stokes respiration. Under anæsthesia--more especially in cerebellar cases--there is considerable risk of respiratory failure (see foot-note, p. 238).

=Vaso-motor changes.= Vaso-motor changes are fairly constant, evidenced by sweats and flushings, _tache cérébrale_, &c.

=Reflexes.= In the earlier stages of the trouble the reflexes may be increased and Babinski’s sign present. In the later stages, all reflexes are abolished.

=Other more general symptoms.= Obstinate constipation, foul tongue and breath, anorexia, deficient urine, loss of bladder and rectal control, are all noticeable features. A well-marked leucocytosis is generally to be observed.

_Symptoms dependent on the localization of the abscess_

(_a_) =Temporo-sphenoidal abscess.= The abscess occupies one of the so-called ‘silent’ areas of the brain, an area merely exercising a word-hearing faculty (see p. 163). Insomuch, however, as auditory power is already impaired or lost from the disease existent in the middle ear, it follows that a temporo-sphenoidal abscess may not give rise to any localizing symptoms whatever. Definite motor symptoms will only be observed when an abscess of considerable size exercises an upward pressure on the lower motor areas, or an inward pressure on the internal capsule. Thus, (1) when the pressure effects are exercised in the _upward_ direction the lower motor areas will suffer with resultant paresis or paralysis of the muscles of the contra-lateral face and upper extremity, and, if the abscess be situated on the left side, aphasia may also be present. And (2) when the pressure is exerted mainly in the _inward_ direction so as to interfere with the internal capsule the motor areas are affected in the reverse order, lower extremity first and face last.

_Aphasia_ will partake of the motor or sensory type according to the situation of the abscess. Thus, motor aphasia indicates pressure on Broca’s area, sensory points to the involvement of the region of the angular gyrus (see p. 163). According to Schmiegelow, some type of aphasia was present in 23 out of 54 cases of otitic temporo-sphenoidal abscess.

_Facial paralysis_, whether due to inward or upward pressure, is of the incomplete or cortical type, the upper face-muscles escaping or being but slightly affected. No difficulty need be experienced in differentiating between the ipso-lateral paralysis which results from destruction of the facial nerve in the aqueductus Fallopii and the contra-lateral palsy dependent on the cortical lesion.

Pressure may also be exercised on the post-Rolandic sensory areas and on the tracts that evolve therefrom, but the general condition of the patient seldom allows of any accurate diagnosis with respect to sensory involvement in general.

When the abscess is of considerable size, both _third_ and _sixth_ nerves may be involved. For instance, the third nerve, emerging from the brain at the anterior border of the pons, and passing along the inner border of the temporo-sphenoidal lobe, is liable to irritation or pressure paralysis. In the former case, the pupil on the affected side will be contracted, in the latter instance dilated. When _ipso-lateral_ third nerve paralysis coexists with paralysis of the opposite face and upper extremity, a condition of crossed paralysis results.

When the sixth nerve is involved the external rectus on the side of the lesion is paralyzed with resultant internal squint. Conjugate deviation of the eyes towards the side opposite to the lesion and secondary lateral nystagmus have both been observed.

Further assistance in the localization may be obtained by careful observation as to the position of the headache, by palpation and percussion of the skull, and by a comparison of the intensity of optic neuritis in the two disks.

(_b_) =Cerebellar abscess.= Many of the symptoms previously described when dealing with brain abscess in general are intensified when the focus of suppuration is situated in the confined space beneath the tentorium cerebelli. Thus, headache is exceptionally severe and more or less localized to the occipital and cerebellar regions. Again, optic neuritis may develop rapidly and reach a high grade of intensity, vomiting is early in onset and of frequent occurrence, whilst certain other symptoms dependent on the increased intracranial pressure--slowing of the pulse, alterations in respiratory rhythm--are correspondingly accentuated.

The more typical _localizing_ symptoms are as follows:--

_Vertigo_ is a prominent symptom, most evident on sudden alteration of position on the part of the patient. He complains, for instance, of great giddiness on sitting up in bed. The sensation of movement may be of self or of objects.

When standing, he tends, when unsupported, to fall or lurch in some particular direction, more commonly, in my experience, towards that side on which the abscess is situated. On this point, however, there is some difference of opinion and, by itself, it cannot be accepted as having any great localizing value.

In some rare cases Dana’s symptom may be noticed--a sudden unexpected attack of vertigo, roaring in the head, relaxation of limbs, and falling to the ground in an unconscious state. This symptom is said to be almost pathognomonic of an abscess (or tumour) situated in the region of the cerebello-pontine angle.

The _cerebellar gait_ can of course only be demonstrated when the patient is in a fit condition to walk. He shows, by the position of the feet, a desire to obtain a wide base of support and staggers on, in his desire to carry out his instructions, usually inclining towards the side on which the lesion is situated. This inclination is probably dependent on the weakness of the muscles of the ipso-lateral side (see below). Another important feature may be observed in the tendency on the part of the patient to turn the head in such a way that he faces somewhat in the opposite direction, the chin being directed towards the opposite shoulder.

_Disturbances of co-ordination_ may be demonstrated by telling the patient to touch the tip of his nose with his finger, or to strike at an object held a foot or two in front of him. Such attempts are characterized by uncertainty and irregularity of movement, accompanied by considerable tremor.

_Paresis or paralysis of the limbs on the ipso-lateral side._ The abscess usually occupies the antero-external aspect of the lateral lobe of the cerebellum, and is so situated that no direct pressure is exercised on the pyramidal fibres. Some weakness--perhaps paralysis--of the muscles of the extremities on the same side as the lesion can, however, usually be demonstrated. According to Luciani, this is explained in the following manner:--between the cortex of the one side and the cerebellum of the other there are certain ‘associated’ fibres, the strength of the impulses sent out from the cortex depending in part on the integrity of these reinforcing cerebellar fibres. In cases of cerebellar abscess these reinforcements are cut off with consequent paresis, or even paralysis, of the muscles of the face, arm, and leg on the same side as the lesion. Associated with this muscular weakness there is usually some increase in the deep reflexes. Some of the pyramidal fibres do not decussate, and, consequently, an ipso-lateral paralysis may be associated with a contra-lateral paresis.

The same lessening of cortical impulses accounts for a weakening in the external rectus of the same side, which muscle, acting with the internal rectus of the sound side, allows of a conjugate deviation of the eyes towards the opposite side, with well-marked _nystagmus_--of a coarse type--on attempting to correct this deviation.

_Retraction of the head and neck._ Retraction of the head and neck, stiffness of the nuchal muscles, and even opisthotonos, may be observed. The existence of these symptoms is always suggestive of meningeal infection, but an abscess of considerable size, even when situated in the anterior part of the lateral lobe of the cerebellum, may so exercise pressure in the downward direction as to cork up that part of the cerebellum which normally extends into the mouth of the foramen magnum. The neighbouring upper cervical nerves may then be irritated or compressed.

_Yawning._ Frequent purposeless yawning is said to be pathognomonic of cerebellar disease (see p. 165).

_Attitude in bed._ More commonly the patient lies curled up in bed in the position of cerebral irritation, perhaps more frequently with the sound side upwards.

(_c_) =Frontal abscess.= The abscess is usually dependent on long-continued suppuration in the frontal sinus, with deficient drainage and spread of disease to the surrounding bone. The abscess may be situated in close relation to the focus of the disease, but, more commonly, it occupies a more posterior position, so much so that direct pressure is exercised on the corona radiata proceeding from the pre-Rolandic or motor area. It would appear also that definite localizing symptoms do not arise until the abscess has attained considerable size. The _general symptoms_ peculiar to all cases of brain abscess are perhaps less definite when the abscess is frontal in position. Thus, although headache may be localized to the frontal region, and although optic neuritis may be present, yet vomiting, alterations in pulse-rate and in respiratory rhythm are less marked than usual.

The _localizing symptoms_ are often reasonably definite, so much so that but little difficulty may be experienced in arriving at a diagnosis.

In the earlier stages of the abscess formation motor irritation may predominate, with the development of _fits of the Jacksonian type_, the lower and more anterior motor areas being first and mainly affected. More commonly, however, attention will be directed towards the nature of the trouble by _paresis or paralysis of the opposite side of the body_. In this case also the lower motor areas--those responsible for the opposite side of the face and upper extremity (also the motor speech-area on the left side of the brain)--are first and chiefly involved. In some cases--more especially when the abscess is of considerable size--definite hemiplegia may result.

In cases of frontal abscess, the _mental condition_ of the patient demands special consideration. Some definite degree of moral perversion will usually be noticed, the patient--presuming that he is in a conscious condition--making himself as objectionable as possible. He will upset his food, disarrange his bedclothes, disobey orders, and even pass his urine and fæces in his bed though well aware of his wrong-doing. When questioned he answers with suspicion, when examined he demands to know the why and the wherefore of the various details of the investigation. An ophthalmoscopic examination is especially difficult to carry out in a satisfactory manner. In a case recently under my care--one in which a frontal abscess was drained three times before a cure was obtained--these curious mental perversions were observed each time, and the patient subsequently acknowledged that he had performed the various acts wittingly, but was unable to deny himself the opportunity of irritating those around him.

It has been stated that these mental changes are only to be observed when the abscess involves the _left_ frontal lobe. In my own experience no such lateral differentiation has been noticed.

_Anosmia_ may be present if the patient is in a condition to respond to the tests requisite to prove the defect. In most cases, however, considerable difficulty will be experienced in applying the tests, and the results obtained are too variable. Anosmia will be associated with impaired power of taste.

_Pupillary changes._ ‘If the abscess is of large size, the pupil on the same side is in a state of stabile mydriasis; if small, it may be sluggish and contracted.’[56]

=The TERMINAL stage.= In _fatal_ cases death results from the pressure exercised by the expanding abscess on the bulbar centres, or from the bursting of the abscess into the ventricular or meningeal spaces. During this terminal stage the pulse becomes very rapid, the respiration irregular and Cheyne-Stokes in character, whilst the temperature rises rapidly, reaching 105-110 degrees F. Invasion of the lateral ventricle is evidenced by violent convulsions, rigidity of the extremities, opisthotonos, retraction of the head, trepidation, and prostration. The pupils become widely dilated, and remain in that condition till death ensues.

=Treatment.= In the operative treatment of _otitic temporo-sphenoidal and cerebellar abscess_ two courses are available:--(1) to trephine directly over the abscess through the squamous or cerebellar regions, postponing mastoid exploration till a later date (the two-stage operation); and (2) to carry out the complete mastoid operation, searching for the ‘stalk’ of the abscess, and draining the abscess into the now-united middle ear and antrum (the one-stage operation).

The former course is advocated by many general surgeons, the latter is the one usually pursued by the aural surgeon. The advantages claimed for the former method--the direct trephining method--are as follows:--

(1) The general condition of the patient is often of so serious a nature as to prohibit the more prolonged procedures essential to the mastoid exploration.

(2) When the exploration is conducted from the infected middle ear, an unsuccessful attempt to find the abscess carries with it an appreciable risk of meningeal and brain infection. Unsuccessful exploration through the ‘clean’ squamous and cerebellar regions presents no such disadvantages.

(3) The drainage as supplied through the trephine hole is often superior to that provided by dilating up the ‘stalk’ of the abscess into the middle ear.

(4) Many general surgeons do not possess that intimate acquaintance with the anatomy of the ear which is necessary to carry out a complicated aural operation.

Each case must be considered on its own merits, but I am inclined to advocate the two-stage method when the diagnosis is reasonably clear that the patient is suffering from temporo-sphenoidal or cerebellar abscess, mastoid exploration being carried out as soon as the patient has recovered from the first operation. When, however, considerable doubt exists as to the position of the abscess--or the nature of the complication in general--it is then advisable to start by exploration of the mastoid and aural regions, further measures being adopted according to the conditions found at the time of operation.

1. The two-stage operation.

_Trephining for temporo-sphenoidal abscess._ A point is chosen on the scalp which lies between 1¹⁄₂ and 2 inches above the centre of the external auditory meatus, and a bradawl is there introduced so as to indent the external table of the skull. A small scalp-flap is framed, one presenting an upward convexity, and all bleeding controlled. The pin of the trephine is applied to the spot previously indicated on the bone and the disk removed. On account of the absence of diploic tissue and consequent approximation of the two tables of the skull, care must be taken to avoid injury to the posterior branch of the middle meningeal artery and to the bulging dura mater.

The dura is then inspected and palpated; absence of pulsation, loss of lustre and tenseness, indicate the probable adjacency of the abscess cavity. The membrane should be crucially incised, all meningeal vessels that cross the line proposed for section being first under-run on either side of that line. The scalpel is lightly applied to the membrane and, as soon as the pia-arachnoid is exposed, the section completed with the blunt-pointed scissors.

The four dural flaps are turned aside and the cortex exposed. At the very apex of the bulging brain, and avoiding all visible vessels, a large blunt-pointed trocar and cannula or, preferably, Horsley’s pus-evacuator is introduced and passed, for not more than 1¹⁄₂ inches, in a direction inwards and slightly forwards, parallel to the roof of the middle ear. The blades of the evacuator must be opened ‘once for each quarter of an inch of brain substance penetrated’ (Macewen). If the trocar and cannula be utilized, similar precautions must be adopted.

In the event of failure to find pus at the first attempt, the evacuator is withdrawn, introduced at the same site, but now passed in other directions--directly inwards, slightly upwards, and finally, slightly backwards, in each case for not more than 1¹⁄₂ inches.

By wide separation of the blades of the evacuator the pus is allowed to escape, to be immediately wiped away by the assistant. Irrigation of the cavity should never be attempted, not so much because of the difficulties attendant on that process, but because of the danger of infecting the neighbouring meningeal regions.

Previous to withdrawal of the evacuator, a small rubber or cigarette drainage-tube is introduced, projecting into the abscess cavity at the one end, and brought out through the scalp-flap at the other. It is advisable to stitch the tube in position.

The dural flaps are replaced in their proper position, but no attempt is made at sewing them together. The scalp-flap is sutured with the aid of a few salmon-gut stitches and the dressings applied. The tube may be shortened daily, and dispensed with after seven to ten days, according to the progress of the case.

_Trephining for cerebellar abscess._ The abscess usually occupies the antero-external aspect of the lateral lobe of the cerebellum. It can be drained with advantage below the level of the lateral sinus and behind the posterior border of the mastoid process.

The patient should be in the semi-prone position, the head as forwardly flexed as the administration of the anæsthetic allows.

The incision starts below the external occipital protuberance, and, following the line of the occipital crest, curves downwards along the posterior border of the mastoid process, terminating at the apex of that prominence. The cutaneo-muscular flap is turned down, every precaution being taken to diminish hæmorrhage, insomuch as severe bleeding may take place from occipital vessels, and from the mastoid and other emissary veins. Hæmorrhage from the former source is controlled with forceps, that from the emissary veins by the introduction of the end of a blunt probe into the orifice of the foramen. More permanent occlusion can be obtained by plugging the foramen with catgut, with a sterilized wooden match, or by means of special ivory, bone, and wooden pegs.

The trephine is applied in such a manner that its circle falls well below the lower level of the lateral sinus and behind the mastoid process. After removal of the disk, the dura mater is cautiously opened by crucial incision and the evacuating instrument introduced, the cerebellum being explored in the forward and slightly inward direction--towards the posterior aspect of the petrous bone. The abscess should be reached within 1¹⁄₂ inches from the opening in the bone. A drainage tube is introduced, stitched in position, in the manner described when dealing with temporo-sphenoidal abscess. This tube should be shortened daily and dispensed with after seven to ten days.

_Trephining for frontal abscess._ An abscess of the frontal lobe is generally situated so far back, and connected with the source of the trouble (the frontal sinus) by so long a ‘stalk’ of infection, that considerable difficulty may be experienced in attempting drainage from the frontal or nasal regions. Moreover, operations conducted through the frontal region are apt to result in considerable deformity. The operation may therefore be conducted with advantage from the temporo-frontal region. In this situation, the bone is thin, the operation can be conducted between the split fibres of the temporal muscle, excellent drainage is supplied, and the scar is inconspicuous.

For a general description of the intermusculo-temporal operation, the reader is referred to p. 121. In this instance, the field of operation is shifted further forwards, otherwise the details are very similar. The skin incision commences above and in front of the external angular frontal process, curves along the temporal crest, and terminates well in front of the ear. The temporal fascia is turned down and the muscle split in the general direction of its fibres, and well retracted on either side. The trephine is applied, the dura mater incised, and the abscess evacuated and drained in the manner previously described. The tube may be removed after seven to ten days.

_The treatment of a chronic encapsuled abscess, wherever situated._ In attempting to evacuate a chronic encapsuled abscess, both the trocar and cannula and the evacuator merely impinge against, and tend to push aside, the dense enclosing wall of the abscess cavity. When such obstruction is suspected, a director should be introduced in the direction of the abscess, and the brain explored till the resistance of the abscess-wall is encountered. With the aid of two narrow spatulæ, or other suitable instrument, the passage through the brain is gently enlarged till the wall of the abscess becomes visible. The margins of the passage through the brain are gently retracted and the abscess-wall freely incised with the knife. After the evacuation of the pus, a drainage tube can be introduced, but, as such a method seldom permits of a permanent cure--the abscess filling up again as soon as the tube is withdrawn--it is generally advisable to attempt the entire removal of the abscess-wall. The cut edges of the capsular incision are seized with narrow-bladed forceps, gentle traction applied, and the surrounding brain substance carefully peeled away. As a rule, there is no great difficulty attendant on this process and the hæmorrhage is seldom severe. The cavity that remains in the brain substance is _lightly_ packed with gauze, this packing being allowed to remain for twenty-four to thirty-six hours, after which it is withdrawn and a little fresh gauze introduced, if necessary. The cavity fills up with extraordinary rapidity, mainly as a result of the expansion and falling together of the surrounding brain (see Figs. 86 and 86a).

2. The one-stage operation.

_Preliminary exploration of the mastoid operation, followed by an investigation of the middle and posterior fossæ of the skull._ To expose the mastoid antrum, the incision commences immediately above and behind the ear, and, carried down to the bone throughout, terminates near the tip of the mastoid process. The soft tissues are peeled away in the forward direction and the cartilaginous ear detached from the posterior and upper boundaries of the bony auditory meatus.

Macewen’s suprameatal triangle and the supramastoid crest are identified, the former landmark being taken as a guide to the communication between the mastoid antrum and the middle ear, the latter representing the uppermost limit of the field of operation.

With the aid of the hammer and chisel the bone is chipped away till the antrum is exposed--on an average this will be situated about three-fifths of an inch deep from the surface. The opening necessarily becomes funnel-shaped, but it should be made as complete as circumstances permit.

As soon as the antrum is exposed, the seeker or nerve-protector should be introduced into the aditus, acting as a protector to the underlying external semicircular canal and facial nerve, and the ‘bridge’ of bone, which now intervenes between the antrum and the middle ear, chiselled away, in the manner indicated in Fig. 80.

The field of operation is now carefully cleansed, cholesteatomata, bone-debris, and ossicles being gently removed, and--with the aid of a head-lamp--a careful search instituted for fistulous tracts, carious bone, &c. This search must be carried out with the greatest gentleness for fear of inducing further complications.

Subsequent procedures vary according to the nature of the conditions found. Thus:--

1. When the diagnosis is uncertain and when the boundaries of the cavity appear fairly healthy, the operation may terminate at this point, a post-meatal flap being formed and the cavity lightly plugged with gauze. The proximal end of the gauze plug is brought out through the enlarged auditory meatus and the ear-flap sewn back with a few salmon-gut sutures.

2. When the evidence points to implication of the _middle_ fossa, the scalp incision is prolonged upwards for about 1 inch and the soft parts retracted. The supra-tegmental extra-dural space can be exposed either by chiselling away the osseous roof of antrum and middle ear, or by means of a separate opening above the level of the supramastoid crest. In the event of the discovery of an _extra-dural_ collection of pus, the purulent material is gently wiped away, free drainage supplied, and the wound closed.

In both this and the preceding case, the progress of the case during the ensuing twenty-four to forty-eight hours will prove whether adequate measures have been adopted.

When the symptoms are suggestive of _brain abscess_, when no extra-dural collection is discovered, and when the dura mater is tense and discoloured, then it becomes necessary to explore the brain. This can be carried out through an opening made in the tegmen or above the level of the supramastoid crest. Which route should be utilized depends on the local conditions. As a general rule, it is advisable to explore through the tegmen when a sinus exists in that situation, and above the supramastoid crest under all other circumstances.

In the latter case, the dura mater is incised crucially and the bulging brain explored in the manner indicated on p. 266. The mastoid region should first be cleansed and packed with gauze, but, even with such precautions, it is obvious that there is some risk of contaminating membranes and brain in the event of failure to discover the abscess cavity--an argument in favour of exploring through the ‘clean’ squamous region (see p. 264).

3. When the evidence points to implication of the _posterior_ fossa, an incision is carried backwards, from the mid-point of the post-aural incision, for about 2 inches, and the soft parts retracted upwards and downwards. With the chisel (or gouge) and hammer, the bone is freely cut away so as to expose (1) the lateral sinus, and (2) the dura mater below and behind the curve of the sinus. As soon as the sinus is exposed, the dura mater may be separated from the bone and the subsinus region exposed with the aid of craniectomy forceps.

The extra-dural space between the posterior aspect of the petrous bone and the lateral sinus region is first inspected, and, in the event of the discovery of a collection of pus, this is gently wiped away and further exploration postponed till the occasion should prove the necessity.

When the indications are of such a nature as to demand _exploration of the cerebellum_, the mastoid region is first cleansed and packed with gauze, after which the dura mater is incised either in front or behind the sinus according to the probable situation of the abscess cavity. After the evacuation of the abscess a drainage tube is stitched in position in the manner previously indicated.

Difficulties and dangers attendant on the process of trephining for brain abscess.

_Failure to find the abscess_ is usually dependent on one of the
following causes:--

(_a_) The abscess may be missed if the localizing features are
misleading, if the abscess be small, and if the exploring instrument
be passed in a faulty direction or to an insufficient depth.

(_b_) The abscess may be traversed but not tapped if unsuitable
exploring instruments be used--an aspirating syringe, for instance,
through which the thick pus will not pass. Even when suitable
instruments are used, the attempt to evacuate the abscess may fail if
the operator does not carry out what may be called a system of
progressive exploration, that is to say, if he does not periodically
open the blades of the evacuator (see p. 266).

(_c_) The abscess may be encountered but not penetrated if the surgeon
has to deal with a chronic abscess, the wall of which is merely
pushed aside by the advancing instrument (see chronic abscess of the
brain, p. 268).

_Complications_ arising during and after the evacuation of the abscess
are as follows:--

1. Leaking into the pia-arachnoid and the development of general
meningeal infection.

2. Perforation of the ventricular spaces.

3. Hæmorrhage.

4. Respiratory failure.

5. Osteomyelitis of the neighbouring diploic tissue.

_General meningeal infection_ will bring about a fatal result.
Fortunately, the general rise of intracranial pressure and the
formation of adhesions between the brain and the overlying membranes
tend to prevent its development.

_Perforation of the ventricular spaces_ may occur under two
conditions: (1) when the abscess is associated with internal
hydrocephalus, and (2) when the exploring instrument is passed too
far.

_Hæmorrhage_ is seldom serious when the operation is carried out with
a light hand, all visible vessels being carefully avoided. In the
event of its occurrence, it may be controlled by lightly packing the
cavity with gauze.

_Respiratory failure_ is most liable to occur when the surgeon is
operating for cerebellar abscess. In the event of its occurrence the
surgeon should complete his trephining with the utmost expedition,
thus relieving the intracranial pressure. Under favourable
circumstances, the respiratory rhythm is soon restored. In the more
serious cases, artificial respiration should be attempted whilst the
surgeon carries on his manipulations, opening the skull as rapidly as
possible.

MENINGITIS

Previous to entering into the question of general meningeal infection, some allusion must be made to the rarer forms of meningitis.

=Serous meningitis.= Quincke demonstrated in 1895 the existence of a serous form of meningitis, one characterized by a sero-fibrinous exudate. He showed that, just as we have to deal with a serous or purulent pleurisy, so we have to consider the possibility of a serous or purulent form of meningitis.

The exudate appears at first sight to differ but slightly from normal cerebro-spinal fluid, being clear, yielding the normal chemical reactions of that fluid, and occupying the subarachnoid region. Later on it becomes slightly turbid, contains a fair quantity of albumen, and is proportionately rich in cellular elements--lymphocytes and polymorphonuclear leucocytes. The membranes are swollen, the vessels dilated, whilst occasionally many minute hæmorrhages may so allow of the escape of red blood-corpuscles as to impart to the exudate a yellowish-red coloration. At a still later stage the exudate becomes flocculent as a result of the deposition of a fibrinous coagulation, a gum-like material forming over the surface of the brain.

=Pachymeningitis externa.= Pachymeningitis externa is almost necessarily dependent on disease of the middle ear, on suppuration in the accessory sinuses of the nose, and on infected fractures of the vault and base. The inflammatory changes primarily involve the external aspect of the dura mater, the external surface of which is injected, roughened with fibrinous exudate, and, in the more chronic cases, covered with granulations. In itself the process seldom gives rise to symptoms, but so soon as the inner surface of the dura shares in the affection (meningitis), or the infection spreads to the venous sinuses (sinus thrombosis), or to the brain (brain abscess), definite symptoms arise pointing to the nature and character of the change.

=Pachymeningitis interna and pachymeningitis interna hæmorrhagica.= As the direct result of alcoholic excess, of syphilitic infection, and of trauma, the inner surface of the dura mater loses its shiny appearance, becomes opaque and thickened, especially in the region of the falx cerebri and over the convexity of the brain. The sodden and œdematous condition of the dura gives rise to a fibrinous and membranous exudate, terminating in the formation of false membranes--one of the factors in the formation of so-called ‘arachnoid cysts’ (see p. 203). These membranes are seen to be attached to the dura mater by means of newly-formed vessels, some of which may rupture, giving origin to blood exudate sufficing to impart to the membranes a brownish-red coloration. In the more marked cases, especially in those of a recurrent nature, the membranes partake of a lamellated type. Occasionally, the hæmorrhages are more excessive, giving rise to the formation of subdural hæmatomata from the partial absorption of which the various types of pachymeningitis hæmorrhagica arise.

These rarer forms of meningitis seldom give rise to such definite symptoms as to allow the surgeon to carry out surgical procedures in their earlier stages. Later on, by reason of the development of cystic accumulations of fluid or other complication, operation may be carried out with a reasonable degree of success. The operative technique adapted to the individual case is discussed under appropriate headings--Jacksonian epilepsy, meningeal cysts, &c.

It is possible that some criticism may be aroused with regard to the non-inclusion of tuberculous meningitis. Insomuch, however, as I have operated on a considerable number of cases of tuberculous meningitis--some intentionally from a decompression point of view, others by reason of doubtful diagnosis--and have never brought about more than some temporary alleviation, I have come to regard such cases as beyond the realms of surgery.

=Acute lepto-meningitis.= This condition will be considered under the more familiar, though less correct, designation--_meningitis_.

Attempts have been made to classify the various forms of meningitis on a bacterial basis. When, however, it is realized that almost any known form of organism may be present in the exudate, and that the symptoms dependent on these various infections closely resemble one another, merely differing in their acuteness and intensity, it would appear that some other form of classification is preferable.

The following method of classification will suffice:--

=1.= =Meningitis of traumatic origin.= The organisms either obtain direct entrance to the meningeal space by means of a compound fracture of the vault or base of the skull, or reach their destination along the course of the numerous emissary and diploic veins that bring the extra- and intra-cranial channels into communication.

=2.= =Meningitis secondary to disease of neighbouring regions.=

(1) The accessory sinuses of the nose and ear.

(2) The bones of the skull.

(3) The soft parts--scalp, orbit, nose, and face.

=3.= =Meningitis secondary to disease of more distant regions.= Through the medium of the blood-stream bacteria may be carried to the meningeal region in many acute infections--more especially in diseases of the lung.

=Some anatomical considerations of meningitis.= The _pia_ is closely applied to the surface of the brain, dipping down into all the fissures, both major and minor. The _arachnoid_ is only reflected into the greater fissures--the mesial longitudinal fissure, the fissure of Sylvius, Rolando, &c. The pia and arachnoid are therefore separated from one another by a potential space over the convolutions themselves, and by an actual space in the region of many of the cortical fissures.

On the under aspect of the brain the two membranes are so disposed and so separated from one another as to form three great basins or cisternæ, three great spaces acting as a water-bed for the brain. These are the _cisterna magna_, the arachnoid bridging over the wide interval between the back part of the under surface of the cerebellum and the medulla, the _cisterna pontis_, the angular space between the pons, medulla, and cerebellum, and the _cisterna basalis_, the arachnoid there covering in the structure situated in the interpeduncular space, including the Circle of Willis.

The subarachnoid space, both cortical and basal, is traversed by numerous trabeculæ which, passing from one membrane to the other, break up the space into innumerable small compartments, all containing cerebro-spinal fluid and all intercommunicating. The cerebral vessels ramify in the space, the tributaries being supported by the framework and bathed in the fluid.

All cranial nerves carry with them in their emergence from the skull a process of both pia and arachnoid, variable in extent, but so arranged that the nerve trunk is surrounded for some distance by a funnel-shaped process of membrane, the cerebral cerebro-spinal fluid being thus brought into connexion with the cervical lymphatic spaces.

With respect to the origin of the cerebro-spinal fluid and its wave of flow, the researches of Leonard Hill tend to prove that it is formed from the lining ependyma and choroid plexuses of the three main ventricles of the brain, passing thence into the spinal cerebro-spinal region and, by means of the foramina of Majendie, Key, and Retzius--apertures in the roof of the fourth ventricle--on to the surface of the brain. From this latter region there appears to be a general tendency for the fluid to pass upwards from the basal aspect of the brain towards the superior longitudinal sinus where it is again absorbed, probably through the medium of the Pacchionian bodies and lacunæ laterales of the venous sinus.

From these few anatomical facts it is manifest (1) that a subarachnoid purulent effusion has every opportunity of spreading widely over the surface of the brain, and (2) that inflammation and its results in the immediate neighbourhood of the roof of the fourth ventricle will tend to impede the normal flow of cerebro-spinal fluid through the foramina in that region, thus inducing a degree of internal hydrocephalus directly proportionate to the degree of obstruction.

Furthermore, it is obvious that the anatomical arrangements are entirely opposed to the possibility of providing adequate drainage in cases of general meningeal infection. It has been suggested that trephine holes should be made on either side of the skull, and that the intervening meningeal space should be washed out between the two apertures. It is, however, impossible to attain such a result, not only because of the futility of attempting to wash through the subarachnoid meshwork, but also on account of the outward bulging of the brain substance through the trephine holes and the corking up of those apertures.

The pus rapidly spreads over the surface of the cerebrum and over the base of the brain, along the sheaths of the emerging cranial nerves, and down the spinal canal. Associated with vascular dilatation there is extensive leucocyte extravasation into the perivascular spaces, the course of the line of the attack being mapped out by white and yellow lines and areas of exudation. Insomuch, also, as the meningeal vessels are in direct continuity with those of the cortex itself, it follows that a well-developed case of meningitis implies a corresponding degree of cerebritis, with red or white softening of the brain substance according to the degree of hæmorrhagic extravasation.

=Symptomatology.= Meningitis is generally sudden in onset and ushered in by a rigor, frequently of a most intense character. Headache is always a marked feature, commonly diffuse, but sometimes localized to the region primarily and mainly affected. The headache is intense and exacerbations are marked, the patient crying out in his agony. There is great mental irritability and all attempts at clinical examination are strenuously resisted.