_Pathology._--When any addition is made to the bulk of matter inside the cranial cavity, room is gained in the first instance by the displacement into the vertebral ca.n.a.l of a certain amount of cerebro-spinal fluid. The capacity of the spinal sheath, however, is limited, and as soon as the tension oversteps a certain point, the pressure comes to bear injuriously on the cerebral capillaries, disturbing the circulation, and so interfering with the nutrition of the brain tissue. As the intra-cranial tension still further increases, the pressure gradually comes to affect the cerebral tissue itself, and so the extreme symptoms of compression are produced. The vagus and vaso-motor centres are irritated, and this causes slowing of the pulse, contraction of the small arteries, and increase of the arterial tension which tends to maintain an adequate circulation in the vital centres in the medulla. The Cheyne-Stokes respiration is due to rhythmical variations in the arterial tension: during the period of fall the centres become anaemic and the respiration fails; during the rise the medulla is again supplied with blood, and breathing is resumed (Eyster).
The parts of the brain directly pressed upon become anaemic, while the other parts become congested, and the nutrition of the whole brain is thus seriously interfered with. Different parts of the brain and cord show varying powers of resistance to this circulatory disturbance. The cortex is the least resistant part, and next in order follow the corona radiata, the grey matter of the spinal cord, the pons, and, last, the medulla oblongata. Hence it is that the respiratory and cardiac centres hold out longest.
_Depressed Bone as a Cause of Compression._--It is more than doubtful whether a depressed portion of bone is of itself capable of inducing symptoms of compression of the brain. When such symptoms accompany depressed fracture, they are to be attributed either to a.s.sociated haemorrhage, or to interference with the circulation and consequent dema which the displaced bone produces. Fragments of bone may, however, aggravate the symptoms by irritating the cerebral tissue on which they impinge.
_Foreign Bodies._--The role of foreign bodies, such as bullets, in the production of compression symptoms is similar to that of depressed bone. That foreign bodies of themselves are not a cause of compression seems evident from the fact that it is not uncommon for them to become permanently embedded in the brain substance without inducing any symptoms. Not only have bullets, the points of sharp instruments, and other substances remained embedded in the brain for years without doing harm, but in many cases the patients have continued to occupy important and responsible positions in life.
_Differential Diagnosis._--It not infrequently happens that a patient is found in an insensible condition under circ.u.mstances which give no clue to the cause of his unconsciousness. He is usually removed to the nearest hospital, and the house-surgeon under whose charge he comes must exercise the greatest care and discretion in dealing with him. In attempting to arrive at the cause of the condition, numerous possibilities have to be borne in mind, but it is often impossible to make a definite diagnosis. The chief of these causes are trauma, apoplexy or cerebral embolism, epileptic coma, alcohol and opium poisoning, uraemic and diabetic coma, sunstroke, and exposure to cold.
The commonest error is to mistake a case of cerebral compression for one of drunkenness. It is scarcely necessary to say that a man who smells of alcohol is not necessarily intoxicated; the drink may have been given with the object of reviving him. It may be that one or other of the above-named conditions has caused the patient to fall, and in his fall he has incidentally sustained an injury to the head, which, however, is in no way responsible for his unconsciousness.
Whenever there is the least doubt, therefore, the patient should be admitted to hospital.
In the first instance, careful search should be made for any sign of injury, especially on the head. The discovery of a severe scalp wound or of a fracture of the skull, in a.s.sociation with the symptoms of concussion or compression, will in most cases raise the presumption that the unconsciousness is due to some traumatic intra-cranial lesion. Examination of the fluid withdrawn by lumbar puncture may furnish useful information (p. 338).
In the absence of evidence of a head injury, the stomach should be washed out and its contents examined to see if any narcotic poison is present. The urine also should be drawn off and examined for alb.u.min and sugar.
In haemorrhage due to the rupture of diseased cerebral arteries (apoplexy), or to embolism, the symptoms are essentially those of compression, and, in the absence of a definite history of injury to the head, it is seldom possible to arrive at an accurate diagnosis as to the cause of the condition. The history that the patient has previously had "an apoplectic shock," and the fact that he is up in years and shows signs of arterial degeneration and of cardiac hypertrophy which would favour such haemorrhage, are presumptive evidence that the lesion is not traumatic.
If a history is forthcoming that the patient is an epileptic, there is a strong presumption that the symptoms are those of _epileptic coma_.
In _alcoholic poisoning_ the examination of the stomach contents will furnish evidence. The patient is not completely unconscious, nor is he paralysed; the pupils are usually contracted, but react; and the temperature is often markedly subnormal. Improvement soon takes place after the stomach has been emptied.
In _opium poisoning_ the general condition of the patient is much the same as in poisoning by alcohol. The pupils, however, are markedly contracted, and do not react to light. When the poison has been taken in the form of laudanum, this may be recognised by its odour.
In the _coma_ of _uraemia_ or of _diabetes_ there is no true paralysis, nor is there stertor. The urine contains alb.u.min or sugar, and there may be dema of the feet and legs.
_Prognosis._--The prognosis depends so much on the nature and extent of the injury to the brain that it is impossible to formulate any general statements with regard to it. It may be said, however, that the symptoms which indicate a bad prognosis are immediate rise of temperature, particularly if it goes above 104 F., the early onset of muscular rigidity, extreme and persistent contraction of the pupils, with loss of the reflex to light, conjugate deviation of the eyes, and the early appearance of bed-sores.
In the majority of cases compression ends fatally in from two to seven days. On the other hand, recovery may ensue after the stuporous condition has lasted for several weeks.
The _treatment_ of compression is considered with the different lesions which cause it; the principle in all cases being to remove, if possible, the cause of the increased pressure within the skull.
#Traumatic dema.#--In practice, cases are frequently met with, particularly in children, that do not conform to the cla.s.sical description of either concussion, cerebral irritation, or compression.
The injury may be followed by a varying degree of concussion which soon pa.s.ses off but leaves the patient in a listless, drowsy state that may persist for days or even for weeks. The cerebration is disturbed, so that while the patient is not unconscious, he is apathetic and has lost his bearings and fails to recognise where or with whom he is. He complains of headache, there is tenderness on percussion over the skull, the knee jerks are diminished or absent, but there is no motor paralysis. In some cases there are localised jerkings, in others generalised convulsive attacks during which the patient becomes deeply cyanosed. The condition differs from compression due to middle meningeal haemorrhage in that it is less severe and is not steadily progressive.
When the symptoms are localised, the condition is probably due to dematous infiltration of the injured portion of brain; when generalised, to increased intra-cranial tension from serous effusion into the arachno-pial s.p.a.ce.
The _treatment_ consists in diminishing the intra-cranial tension by purgation, leeches, bleeding, or lumbar puncture, or if life is threatened, by opening the skull over the seat of injury, or failing evidence of this, by a decompression operation in the temporal region.
INTRA-CRANIAL HaeMORRHAGE
Apart from the haemorrhage that accompanies laceration of brain tissue, bleeding may occur inside the skull, either from arteries or from veins. The effused blood may collect either between the dura mater and the bone (_extra-dural haemorrhage_), or inside the dura (_intra-dural haemorrhage_).
#Middle Meningeal Haemorrhage.#--The commonest cause of extra-dural haemorrhage is laceration of the middle meningeal artery. This artery--a branch of the internal maxillary--after entering the skull through the foramen spinosum, crosses the anterior inferior angle of the parietal bone, and divides into an anterior and a posterior branch which supply the meninges and calvaria (Fig. 186). Either branch may be injured in a.s.sociation with fractures, or from incised, punctured, or gun-shot wounds. The vessel may be ruptured without the skull being fractured, and sometimes it is the artery on the side opposite to the seat of the blow that is torn. The most common situations for rupture are at the anterior inferior angle of the parietal bone, in which case the anterior branch is torn (90 to 95 per cent.); and on the inner aspect of the temporal bone, where the posterior branch is torn (5 to 10 per cent.).
[Ill.u.s.tration: FIG. 186.--Relations of the Middle Meningeal Artery and Lateral Sinus to the surface as indicated by Chiene"s Lines.
(After Cunningham.)]
It is probable that the size of the haemorrhage depends on the nature, extent, and severity of the injury to the head. The recoil of the skull after the blow separates the dura from the bone, and if the meningeal artery is lacerated or punctured, blood is effused into the s.p.a.ce thus formed (Fig. 187). A localised blow therefore results in a small area of separation and a correspondingly small clot; while a diffuse blow is followed by more extensive lesions. It is believed that, once the dura is partly separated, the force of the blood poured out from the lacerated artery is--on the principle of the hydraulic press--sufficient to continue the separation.
[Ill.u.s.tration: FIG. 187.--Extra-Dural Clot resulting from haemorrhage from the Middle Meningeal Artery.]
_Clinical Features._--The typical characteristics of middle meningeal haemorrhage are met with only when the bleeding takes place between the dura and the bone. Under these conditions the symptoms of concussion are usually most prominent at first, and those of compression only ensue after a varying interval, during which the patient as a rule regains consciousness. In some cases, indeed, he is able to continue his work, or to walk home or to hospital, before any evidence of intra-cranial mischief manifests itself. This "lucid interval" helps to distinguish the symptoms due to middle meningeal haemorrhage from those of laceration of the brain substance, as in the latter the symptoms of concussion merge directly into those of compression.
Lumbar puncture may aid in the differential diagnosis between extra-and intra-dural haemorrhage, as blood is present in the fluid withdrawn in the latter, but not in the former.
A few hours after the accident the patient experiences severe pain in the head, and he usually vomits repeatedly. For a time he is restless and noisy, but gradually becomes drowsy, and the stupor increases more or less rapidly until coma supervenes. The pulse usually becomes slow and full. The respiration is rapid (30 to 50), and becomes greatly embarra.s.sed and stertorous. The temperature progressively rises, and before death may reach 106 F., or even higher. Monoplegia, usually beginning in the face or arm on the side opposite to the lesion, gradually comes on, and is followed by hemiplegia, from pressure on the motor areas, underlying the clot. The condition of the pupils is so variable as to have no diagnostic value; but if both are widely dilated and irresponsive to light, the prognosis is grave.
Death usually ensues in from twenty-four to forty-eight hours, unless the pressure within the skull is relieved by operation; even after removal of the clot death may ensue if the brain has been lacerated, or if there is haemorrhage at the base.
When the haemorrhage takes place from the anterior branch, the clot tends to spread towards the base, and may press upon the cavernous sinus, causing congestion and protrusion of the eye, with paralysis of the oculo-motor nerve and wide dilatation of the pupil.
In some cases of middle meningeal haemorrhage there is no gross injury to the brain; the area underlying the clot is merely compressed and emptied of blood, and, on being exposed, the brain is found flattened, or even deeply indented by the blood-clot, and it does not pulsate. If the clot is removed, the brain may regain its normal contour and its pulsation return. The mortality is over 50 per cent.
If the fracture is compound, the blood can escape, and therefore the pressure symptoms are less evident or may be entirely absent.
It is a fact of some medico-legal importance that haemorrhage from the middle meningeal may not take place till some days, or even weeks, after an injury, which at the time was only attended with symptoms of concussion. This condition is known as _traumatic apoplexy_.
_Treatment._--Immediate operation is imperatively called for, not only to arrest the haemorrhage and remove the clot, but also to ward off the dema of the brain, which is often responsible for the fatal issue.
When there is no external wound, the point at which the skull is to be opened is determined by the symptoms; for example, paralysis of the arm and face on one side indicates trephining over the centres governing these parts on the side opposite to the paralysis.
If the bleeding cannot otherwise be arrested it may be necessary to ligate the external carotid artery. It has been suggested by J. B.
Murphy that, when the patient is seen while the symptoms of compression are coming on, instead of trephining, the haemorrhage from the meningeal vessels should be arrested by applying a ligature to the external carotid, under local anaesthesia.
Injury to the #internal carotid# artery within the skull may result from penetrating wounds, or may be a.s.sociated with a fracture of the base. It is almost invariably fatal. In some cases a communication is established between the artery and the cavernous sinus, and an arterio-venous aneurysm is thus produced. Ligation of the internal carotid in the neck or of the common carotid is the only feasible treatment.
Injuries of the #venous sinuses# may occur apart from gross lesions of the skull, but as a rule they accompany fractures and penetrating wounds. The transverse (lateral), superior sagittal (longitudinal), and cavernous sinuses are those most frequently damaged. On account of the low pressure in the sinuses, spontaneous arrest of extra-dural haemorrhage usually takes place, and recovery ensues. In some cases, however, the amount of blood extravasated is sufficient to cause compression. If the dura mater is torn, and the blood pa.s.ses into the sub-arachnoid s.p.a.ce, it may spread over the whole surface of the brain. Sometimes the bleeding only commences after a depressed fracture has been elevated.
In the presence of an open wound, the venous source of the bleeding is recognised by the dark colour of the blood and the continuous character of the stream. It may be arrested by pressure with gauze pads or by packing a strand of catgut into the sinus (Lister), or, if this fails, by grasping the sinus with forceps and leaving these in position for twenty-four or forty-eight hours. A small puncture in the outer wall of the sinus may be closed with sutures. Signs of increasing compression call for trephining and opening of the dura if this is necessary to admit of the clot being removed.
#Intra-cranial Haemorrhage in the Newly-Born.#--An extravasation of blood into the arachno-pial s.p.a.ce frequently occurs during birth. The observations of Cushing seem to show that this is usually due to tearing of the delicate cerebral veins which pa.s.s from the cortex to the superior sagittal sinus, from the strain put upon them by the overlapping of the parietal bones, in the moulding of the head. It may sometimes be due to an excessive degree of asphyxia during birth. The extravasation is usually most marked over the central area of the cortex near the middle line, and it is often bilateral.
This condition is most frequently met with in a first-born child--and more often in boys than in girls--the labour having been prolonged and difficult, and the presentation abnormal. There is usually a history that the infant was deeply cyanosed when born, and that there was difficulty in getting it to breathe. As a rule, there is no external evidence of trauma. The anterior fontanelle is tense and does not pulsate, the pulse is slow, and for several days the child appears to have difficulty in sucking and swallowing, and is abnormally still. In the course of a few days definite symptoms of localised pressure appear. It is noticed that one leg or arm, or one side of the body is not moved, or both sides may be affected; when the paralysis is bilateral, the absence of movement is more liable to be overlooked.
The infant may suffer from convulsions; there may be paralysis of certain of the ocular muscles, and inequality of the pupils; sometimes there is blindness. Persistent rigidity of the limbs, with turning of the thumbs towards the palm, is present in some cases. Lumbar puncture may reveal the presence of blood corpuscles in the cerebro-spinal fluid, and increase in the tension of the fluid.
If untreated, the condition is usually followed by the development of spastic paralysis of one or more limbs, on one or on both sides of the body (Little"s disease), by blindness, deafness, and varying degrees of mental deficiency, or by Jacksonian epilepsy.
_Treatment._--To obviate these after-effects the clot may be removed by raising an osteo-plastic flap, including nearly the whole of the parietal bone. The operation should be undertaken within the first week or two, and great care must be taken to keep up the body-warmth, and to prevent undue loss of blood. It may be necessary to operate on both sides, an interval being allowed to elapse between the two operations.
For the immediate relief of increased intra-cranial tension, the daily withdrawal of 10-12 c.c. of cerebro-spinal fluid by lumbar punctures may be employed, or a sub-temporal decompression operation may be performed.
WOUNDS OF THE BRAIN
#Wounds of the Brain.#--_Incised_ wounds of the brain usually result from sabre-cuts, hatchet blows, or circular saws. A portion of the scalp and cranium may be raised along with a slice of brain matter, and in some cases the whole flap is severed. The extent of the injury, the conditions under which it is received, and the liability to infection, render such wounds extremely dangerous.
_Punctured wounds_ may be inflicted on the vault by stabs with a knife or dagger, or by other sharp objects, such as the spike of a railing.
More frequently a pointed instrument, such as a fencing foil, the end of an umbrella, or a knitting needle, is thrust through the orbit into the base of the brain. Occasionally the base of the skull has been perforated through the roof of the pharynx, for example, by the stem of a tobacco-pipe. All such wounds are of necessity compound, and the risk of infection is considerable, particularly if the penetrating object is broken and a portion remains embedded within the skull. The infective complications of such injuries are described later.