BRAIN, SURGERY OF. It is common knowledge that surgery as a whole was "released" by the discoveries of Pasteur and Lister, so that the remarkable technical achievements of the surgeon to-day are the result of no more than fifty years' col lective experience. Attention was at first focussed chiefly on the surgery of the abdomen and limbs, and so great and so rapid were the advances made in these spheres that something approach ing technical perfection has been reached. The surgery of the • brain made slower progress because the problems involved were of a much more intricate nature, cases were fewer, and accurate diagnosis, an absolute pre-requisite for good surgery, more diffi cult. The bony skull renders exposure difficult, access is often far from perfect, and a very small error in localization of the lesion suffices to mar the result. Add to this the fact that the tension inside the skull in tumour cases is greatly increased, so that the brain tends to bulge into the opening made and render exploration difficult, unless the pathological lesion happens to be superficial.
The brain is enclosed within a bone capsule and enveloped in membranes which protect it and carry blood vessels to it. A thin film of cerebro-spinal fluid covers it, but normally so accurately does the skull fit the brain that the convolutions impress the bone, and a plaster cast of the interior of a dried skull reproduces faintly the pattern of the brain which once inhabited it. This fact has been of great value to the comparative- and palaeo-anatomist. In spite of this close fitment, there is normally no pressure of bone on the brain. As the brain develops and expands the bone is its servant and never its master; we no longer believe that the bone may stop growing before the brain is fully developed. Thus in a case of maldevelopment of the skull with an immature brain within, we now believe the im maturity of the brain to be the primary factor. Incisions through the bone with the object of releasing a supposedly imprisoned brain have been done in the past but without profit, for the inter vention was based on wrong premises.
It will be understood that there is very little room inside the skull to accommodate any extra bulk, such as a tumour, abscess, collection of blood or fluid and indeed any such addition will in variably produce recognizable effects.
The art of making openings in the skull was known to the ancients, as many recently recovered crania indisputably inform us. The methods employed have been the subject of much speculation and argument, and seem to have ranged from attrition with flint implements to drilling and cross-hatching. By trepanation, an obsolescent word, we mean the making of a hole by chisel or gouge ; by trephining, the cutting out of a disk of bone by a special ring-saw. To-day the majority of surgeons use a drill and burrs, hand or electrically driven ; great ingenuity is being shown in planning rapid and safe methods. It might be thought that any competent surgical engineer could easily invent some power-driven tool which would reduce the time and effort required to cut a flap of bone (which ought to be replaceable). The problem is far from simple, how ever, as the dura mater adheres to the inner surface of the bone sufficiently strongly to necessitate much safe-guarding, for it is essential that the brain and its coverings should remain un injured. A number of clever appliances are in existence, but, as is often the case, the more ingenious the less generally useful are they.
The operation in most general use to-day is that known as the "osteo-plastic flap," where a flap of scalp and bone of large diameter is turned down and when carefully replaced gives an excellent cosmetic result. The exposed dura mater is then incised and the convolutions laid bare. A tumour may at once be seen but if not the brain tissue is carefully probed to detect a difference in resistance. A cyst may thus be encountered and drained. It is surprising how little disturbance this gentle exploration causes if done at a well chosen spot. The whole procedure can be carried out under local anaesthesia. Brain tissue is absolutely insensitive and can be cut without the conscious patient being aware of it. The dura mater and vessels are supplied with sensory nerves and it is only owing to this that headache is possible.
The common subtemporal decompression is done by splitting the fibres of the temporal muscle, boring or cutting through the bone, and enlarging the bony opening with nibbling forceps. The dura mater must be opened as it is so strong that, undivided, it will prevent the brain from prolapsing, and little or no relief of pressure will result. The pituitary gland tumour is attacked through a frontal flap or alternately through the nose after removal of the cartilage and bone in the nasal septum.
Head injuries are increasing in number owing to the development of mechanical transport and the accidents to all classes of the community which are its inevitable consequence. The skull possesses a considerable degree of elasticity and may be deformed for an instant by a blow without solution of con tinuity (i.e., fracture). In that instant very serious damage may be inflicted on the brain, the problem in physics being one of hydro-dynamics on a fluid and semi-fluid content in a rigid con tainer. Very often the skull is broken, but the immediate out look for the patient and the longer view of his future depends very little on fracture, per se, but much more on the extent of the brain injury. For various reasons the floor or "base" of the skull breaks more readily than the cupola, and fractures of the cranial base are the common injuries. On the whole it may be laid down that objects of small mass and high velocity tend to produce local injury of the skull (depressed fractures), whilst those of great mass and low velocity tend to deform the skull as a whole and cause bursting fractures (Trotter and Wagstaffe) usually in the base but extending up from the point of impact. Treatment is essentially on conservative lines, except in depressed fractures.
Concussion, a condition characterised by unconsciousness and associated with shock, is the common result of severe cranio cerebral injury. It varies in degree from momentary "stunning" (as when a boxer is knocked-out in the ring) to profound uncon sciousness lasting hours or days. Delay in recovery is due to oedema of the brain, to the occurrence of minute haemorrhages dotted throughout, or rarely to a large local effusion of blood causing cerebral compression. The oedema is best treated by hypertonic salines (see below), the effusion by operation which, be it noted, is only occasionally indicated.
The only pathway by which a stab can easily reach the brain is through the roof of the orbit, and many cases are on record of accidental injury by this route, for example, penetration by the ferrule of an umbrella, fall on a spike and so on. The danger of infection is great if the patient immediately survives as he often does.
In gun-shot wounds the great factor is the velocity and size of the missile. At short range the cranial capsule will positively burst in pieces, just as water will be ejected from a tub by the passage of a high velocity bullet. If the dura mater is torn (as it will be save with glancing wounds or a spent projectile) infection ensues unless an immediate operation is undertaken to excise the wound in scalp and bone and suck out spicules and diffluent brain matter. The projectile should be removed if it has not traversed too far but it must be most accurately localised by X-Rays first. The defects in the bone, results of gun-shot wounds and rarely of fractures, may call for closure by bone-grafts or celluloid plates (Sargent), but the wounds must be long healed and sterile first.
It has been remarked that any effu sion or growth inside the skull must soon compress the brain. The grey and white matter which constitutes the brain, though soft in texture, is incompressible as water (Monro-Kellie doc trine), so that only the fluids circulating within it, blood and cerebro-spinal fluid, can be squeezed out. Severe headache is the earliest symptom, and continued violent headache in a previously healthy person is always suspicious. Vomiting is a common ac companiment, owing to anaemia of the vital centres in the medulla oblongata. Congestion of the optic nerves is usually present and will lead to blindness if the condition is not relieved by removal of the cause or alternatively by the provision of an opening in the skull to reduce the pressure (decompression).
The commonest cause of raised intra cranial pressure is tumour of the brain, by no means a rare affec tion. These growths produce local destructive effects from which the situation of the tumour may be deduced (disturbance of motion and sensation of various kinds). But their outstanding feature is the headache and general misery which they induce by developing in a confined space where there is no margin for any foreign or extra bulk. The local effects of brain tumours are dealt with elsewhere (see NEUROPATHOLOGY) as is their nature (see
