#Lepto-meningitis.#--If the infection spreads to the adjacent arachno-pia (_localised lepto-meningitis_), adhesions usually form, and shut off the infected area from the general arachno-pial s.p.a.ce.
Pus may form among these adhesions, const.i.tuting a _sub-dural abscess_, and may infiltrate the superficial layers of the cortex (_purulent encephalitis_, or _meningo-encephalitis_) (Fig. 194). The symptoms are similar to those of extra-dural abscess, but may be more severe; and it is seldom possible to distinguish between them before exposing the parts by operation. The treatment is carried out on the same lines.
[Ill.u.s.tration: FIG. 194.--Diagram of Sub-Dural Abscess.]
_Acute General Lepto-Meningitis._--In bone lesions, particularly compound fractures, infection of the arachno-pia may take place before protective adhesions form, and a diffuse lepto-meningitis results. The open structure of the arachno-pial membrane favours the rapid spread of the infection, which may extend over the surface of the hemispheres, or downwards towards the base (_basal meningitis_), or in both directions. The process is at first attended with a copious effusion of cerebro-spinal fluid into the arachno-pial s.p.a.ce and into the ventricles (_serous lepto-meningitis_), but this fluid tends to become purulent, the pus forming in a thin layer over the surface of the brain, and in the sulci between the convolutions (_purulent lepto-meningitis_). The membranes are congested and thickened, the veins of the arachno-pia engorged, and the superficial layers of the cortical grey matter may share in the process (_encephalitis_).
_Clinical features._--The earliest and most prominent symptom is violent pain in the head, often referred to the frontal region, or, in cases starting from middle ear disease, to the temporal region. This is accompanied by a sudden rise of temperature, usually without an antecedent rigor; the temperature remains persistently elevated (102 to 105 F.), and the pulse is small, rapid, and irregular both in rate and force. The patient, especially if a child, is extremely irritable, all his sensations are hyper-acute, and he periodically utters a peculiarly sharp, piercing cry.
Vomiting of the cerebral type--that is, unattended with nausea and not related to the taking of food or to gastric disturbance--is common, and persists through the illness. The bowels are usually constipated.
There is an increase in the number of leucocytes in the cerebro-spinal fluid, and organisms also are found in the fluid. As this does not occur in cerebral abscess, examination of the cerebro-spinal fluid may be useful in differential diagnosis. There is a higher leucocytosis in the blood in meningitis than in cerebral abscess.
When the inflammation is most marked over the cerebral hemisphere, there may be paralysis of the side of the body opposite to the seat of the original lesion; sometimes there is erratic rigidity of the limbs, sometimes clonic spasms of groups of muscles. The superficial reflexes disappear early on both sides; the abdominal reflexes being lost sooner than the knee-jerks. In basal meningitis, temporary squinting due to irritation of the ocular muscles, retraction of the head, and an excessively high temperature are usually prominent features. The pupils at first are equally contracted; later they become dilated and fixed. Both optic discs are dematous and swollen.
Gradually the patient becomes unconscious, shows signs of increasing intra-cranial tension, slowing of the pulse, and laboured respiration, and the condition almost always proves fatal within three or four days.
_Treatment._--The treatment consists in removing the source of infection when this is possible, but as a rule little can be done to arrest the spread of the meningitis or to ward off its effects. In cases resulting from a sub-dural abscess in relation to a compound fracture, a sinus phlebitis, or an erosion of the tegmen tympani, an attempt should be made, after exposing this, to purify and drain the meningeal s.p.a.ces. Temporary relief of symptoms sometimes follows the withdrawal of cerebro-spinal fluid by repeated lumbar puncture, bleeding by leeches or cupping, or the use of an ice-bag or Leiter"s tubes. The bowels should be freely moved by purgatives or enemata.
_Cerebro-spinal Meningitis._--This form of meningitis, which is due to the _diplococcus intracellularis_, may occur sporadically, but is more frequently met with in an epidemic form. It is attended with the formation of a profuse sero-purulent exudate, which covers the brain, the cord, the nerves, and the membranes.
The clinical features are similar to those of acute general lepto-meningitis, and in sporadic cases the diagnosis is only completed by discovering the diplococcus intracellularis in the fluid withdrawn by lumbar puncture. Although recovery sometimes takes place, the disease is attended with a high mortality. In the early stages, before the exudate has become too thick, repeated lumbar puncture followed by the injection of Flexner"s serum has proved beneficial.
Recovery may be attended with paralysis of one or other of the cranial nerves.
CEREBRAL AND CEREBELLAR ABSCESS
#Abscess due to Middle Ear Disease.#--The most common cause of abscess in the brain is chronic middle ear disease, and the majority of cerebral abscesses are therefore situated in the temporal lobe. Some are due to direct spread from a collection of pus in relation to an erosion of the tegmen tympani, either inside or outside the dura, others to infection carried by the veins, and in this way the infective material reaches the white matter; less frequently infection from the middle ear takes place along the peri-vascular lymph s.p.a.ces.
Macewen has pointed out that cerebral abscess never occurs from pyogenic organisms pa.s.sing from the middle ear by way of the internal auditory meatus, although lepto-meningitis may do so. Cerebral abscess is much more frequently met with in the white matter of the centrum ovale than in the cortex, and in the majority of cases the abscess is single.
The _pus_ is often of a greenish-yellow colour, or it may be dark brown from admixture with broken-down blood-clot; in some cases it is thin and serous and contains sloughs of brain matter, and it frequently has a ftid odour. In quant.i.ty it varies from a few drops to several ounces.
The _arachno-pia_ over an abscess usually has a turbid and milky appearance.
In an acute abscess the surrounding _brain tissue_ is engorged and infiltrated with pus; in a chronic abscess it is condensed, and the pus may be encapsulated by the formation of a zone of young fibrous tissue round its periphery. In this condition the abscess may remain "latent," giving rise to no symptoms for many weeks or even months.
_Clinical features._--The _initial_ formation of pus in the cerebral tissue is a.s.sociated with the sudden onset of severe pain in the head, shivering and well-marked cutis anserina, and vomiting of the cerebral type. The discharge from the ear usually diminishes or may even cease.
As a _localised abscess_ develops the patient gradually pa.s.ses, into a stuporous condition; he does not lose consciousness, but, his cerebration is slow, he seems unable to sustain his attention, for any length of time, and he answers questions "slowly, briefly, but, as a rule, correctly" (Macewen). The pain in the region of the ear becomes less intense, but the mastoid and temporal areas on the affected side are tender on percussion. The temperature falls, and, as a rule, remains subnormal. Rigors are unusual: their occurrence usually indicating the development of some complication such as sinus phlebitis. The pulse is full, regular, and slow (40 to 60). Vomiting frequently occurs, and the bowels are often obstinately constipated.
There is no actual paresis, but there is a "gradual diminution of the ability to apply his strength." The superficial reflexes are late of disappearing and the disturbance is unilateral. The optic discs are moderately swollen. "The face is expressionless, pa.s.sive, and cloudy.
It may a.s.sume a meaningless smile, with which the features are not lit; it is too mechanical" (Macewen).
_Differential Diagnosis._--In the early stages it is often difficult to distinguish between meningitis and cerebral abscess. The chief points on which reliance is to be placed are that in meningitis the pulse shows an irregularity, both in rate and force, which is wanting in cases of uncomplicated abscess. In meningitis the temperature is raised, while in abscess it is persistently subnormal. The superficial reflexes, particularly the abdominal reflexes, disappear early in meningitis and the disturbance is bilateral; in abscess they are slower to disappear, and one side only is affected. Retraction of the neck, when present, is a characteristic sign of meningitis. In meningitis the optic discs are highly dematous and are more swollen than in abscess, and the condition is equally marked on the two sides.
_Localisation of Cerebral Abscess--Temporal Abscess._--The existence of middle ear disease is always presumptive evidence that the abscess is in the temporal lobe on the same side. A small abscess in this lobe may produce no localising symptoms; one of large size may press indirectly on the motor cortex, on the fibres pa.s.sing through the internal capsule, or on individual cranial nerves.
It is important to observe the order in which paralysis of the opposite side of the body comes on. When it begins in the face and pa.s.ses successively to the arm and leg, the pressure is on the cortical centres. When the paralysis progresses in the opposite direction--leg, arm, face--the pressure is on the nerve fibres pa.s.sing through the internal capsule (Fig. 195). The paralysis may be spastic in lesions of the cortex or internal capsule; if it is flaccid the lesion is almost certainly cortical.
[Ill.u.s.tration: FIG. 195.--Diagram ill.u.s.trating Sequence of Paralysis, caused by abscess in temporal lobe. (After Macewen.)]
Motor aphasia may result from pressure on the left inferior frontal convolution; auditory aphasia from abscess in the posterior part of the superior temporal convolution. Ptosis and lateral squint, with a fixed and dilated pupil, indicates pressure on the oculo-motor nerve of the same side.
Abscess in the _parietal lobe_ gives rise to paralysis of the face and limbs on the opposite side of the body. Abscess in the _occipital lobe_ produces interference with the visual functions. An abscess in the _frontal lobe_ may give rise to no localising symptoms, but if it is on the left side, the power of making co-ordinated movements may be lost--apraxia--or the motor speech centre may be implicated.
_Terminal Stage._--If left to itself, a cerebral abscess usually ends fatally by causing gradually increasing stupor and coma, or by bursting, either into the ventricles or into the sub-arachnoid s.p.a.ce, and setting up a diffuse purulent lepto-meningitis.
When the _abscess bursts into the ventricles_, the patient suddenly becomes much worse and dies within a few hours. "The pupils become widely dilated, the face livid, the respiration greatly hurried, and either shallow or stertorous. The temperature rises within a few hours with a bound from subnormal to 104 to 105 F.; the pulse from 40 or 50 per minute quickly reaches 120 and over. There are muscular twitchings all over the body, possibly a.s.sociated with convulsions and tetanic seizures, and these are followed by coma and speedy death"
(Macewen).
Spontaneous evacuation of a temporal abscess may take place through the middle ear.
#Cerebellar Abscess.#--Next to the temporal lobe, the cerebellum is the most common seat of abscess. Cerebellar abscess is usually due to spread of infection from a thrombosed sigmoid sinus, either directly from a sub-dural abscess formed in relation to the walls of the sinus, or by extension of the thrombotic process along the cerebellar veins.
While the abscess is small, it may give rise to few symptoms, and the patient may be able to go about, but as it increases in size serious symptoms develop. There may be nystagmus, and the patient suffers from vertigo, and is unable to co-ordinate his movements. If he attempts to walk, he reels from side to side; even when sitting up in bed, he may feel giddy and tend to fall, usually towards the side opposite to that on which the abscess is situated. The head and neck are retracted, the pulse is slow and weak, and the temperature subnormal. There is frequent yawning, and the speech is slow, syllabic, and jerky. There may be optic neuritis and blindness. There is sometimes unilateral or even bilateral spastic paralysis of the limbs from pressure on the medulla oblongata. The respiration may a.s.sume the Cheyne-Stokes character, occasionally being interrupted for a few minutes, while the heart continues to beat vigorously. This arrest of respiration is especially liable to occur during anaesthesia.
_Treatment._--The abscess having been localised, the skull must be opened and the pus removed.
#Abscess from causes other than Middle Ear Disease.#--From the _nasal pa.s.sages_, infection may spread to the interior of the skull directly through the walls of the frontal, ethmoidal, or sphenoidal air sinuses, or indirectly by way of the veins, and give rise to a cerebral abscess, usually in the frontal lobe. The symptoms are similar to those of abscess following middle ear disease, but focal symptoms are seldom present. When the abscess is on the left side, apraxia and motor aphasia may be present. Spontaneous evacuation may take place by the abscess bursting into the nose through the cribriform plate.
The treatment consists in trephining through the frontal bone or through the temporal fossa, according to the site of the abscess and its seat of origin. The primary focus of infection must also be dealt with.
In _infected compound fractures_, an abscess may form in the cortical grey matter within a few days of the injury from direct spread of infection from the bone and membranes. This is usually a.s.sociated with a spreading lepto-meningitis, the symptoms of which predominate. The condition usually proves fatal, but by opening up the original wound, removing depressed fragments of bone, and establishing drainage, the patient"s life may be saved.
There is evidence that an abscess may form in the brain after a simple contusion without fracture or other external injury (Ehrenvooth).
An abscess may develop in the white matter of the centrum ovale some weeks, or even months, after an injury, particularly if a fragment of bone or a foreign body has been driven into the brain. If the infection has spread along the track of the missile, the abscess is usually near to the seat of the brain injury, but if it is due to spread of a thrombo-phlebitis it may be a considerable distance from it, even on the opposite side of the head. These chronic abscesses are usually in the parietal or frontal lobes, and as the pus is encapsulated they may remain latent for long periods, during which they may cause some degree of headache, neuralgic pains in the distribution of the trigeminal nerve, and occasional rises of temperature. When the abscess becomes active, general symptoms similar to those of other forms of abscess develop, and there may be localised paralysis of the opposite side of the body, the distribution of which depends upon whether the cortical centres or the motor fibres are implicated.
The treatment consists in opening up the original wound, removing any depressed bone or foreign body that may be present, and establishing drainage.
_Bronchiectasis_ and other infective diseases of the lungs are less common causes of cerebral abscess, which is usually single, and may occur in any part of the brain.
_Disease of the bones of the skull_, such as osteomyelitis or syphilis, may be followed by cerebral abscess.
Abscesses of _pyaemic_ origin are usually multiple, and may occur both in the cerebrum and in the cerebellum; they are not amenable to surgical treatment.
SINUS PHLEBITIS
Inflammation of the intra-cranial venous sinuses is due to the spread of infection from a local focus of suppuration; by far the most frequent cause is chronic suppuration in the middle ear. Less common sources of infection are erysipelas of the face or scalp, infective conditions of the mouth or nose, and diseases of the bones of the skull.
The organisms may reach the affected sinus directly by continuity of tissue, as, for instance, when the transverse (lateral) sinus becomes infected from a focus of suppuration in the mastoid process spreading through the bone to the sigmoid groove and involving the walls of the vessel; or they may reach it by extension of thrombosis in a tributary vein--for example, when the superior sagittal (longitudinal) sinus is infected from an anthrax pustule of the lip, which has caused thrombosis of the emissary vein that pa.s.ses through the foramen caec.u.m.
The pathological changes are the same as occur in the suppurative form of thrombo-phlebitis in the peripheral veins (Volume I., p. 285). The soft clot that forms adheres to the inflamed wall of the sinus, and, being infected with pyogenic bacteria, it soon undergoes purulent disintegration.
The infective process may spread backward along tributary vessels, and so give rise to cerebral or cerebellar abscess, or to purulent meningitis; or it may spread into the internal jugular vein and lead to the development of a diffuse purulent cellulitis along its course.
General pyaemic infection may take place from pus or bacteria getting into the circulation, either directly or by reversed flow through tributary veins. Infective emboli are liable to lodge in the lung or pleura, and set up pulmonary abscess, gangrene of the lung, or empyema.
_Clinical Features._--In all cases, pain in the head, referred to the region of the affected sinus, and so severe as to prevent sleep, is an early and prominent feature. The patient is usually excited, hypersensitive, and irritable in the early stages, and becomes dull and even comatose towards the end. Rigors, followed by profuse perspiration, occur early and increase in frequency as the disease progresses. The temperature is markedly remittent, varying from 103 to 106 F. (Fig. 196). The pulse is rapid, small, and thready. Loss of appet.i.te, vomiting, and diarrha are almost constant symptoms.