OPERATIONS UPON THE CRANIUM.

The fissure of Rolando is the anatomical landmark whose position it is important to determine with reference to a number of modern surgical procedures, for around it cluster most of the motor areas or centres. It commences at the middle line about 56 per cent. of the distance backward from the glabella (root of the nose) to the inion (occipital protuberance), and, passing downward and forward, makes with the middle line an angle of 67 to 69 degrees. For most purposes it begins half an inch back of a point midway between the glabella and inion. It may be easily found by Chiene’s method, which consists in folding a square piece of paper diagonally and folding this again; after which it is three-quarters unfolded, the acute angle then representing 67¹⁄₂ degrees. If this be properly applied to the skull, one edge of its surface can be made to fall directly over the Rolandic fissure. The fissure may also be located by a simple instrument known as the cyrtometer—a gauged metal strip having a sliding arm upon it, which, when the long strip is placed over the longitudinal sinus (i. e., the middle line of the skull), can be made to fall directly over the fissure. While neither of these methods is invariably and minutely exact, either of them is sufficiently accurate for all practical purposes.

The fissure of Sylvius may be indicated by a line drawn from a point 3 Cm. behind the external angular process to a point 2 Cm. below the most prominent part of the parietal eminence. The short and ascending limb of this fissure is of relatively small importance in this connection.

Reid’s base-line, so called, is a line drawn from the inferior margin of the orbit backward through the centre of the external auditory meatus. It is a line often alluded to in cranial topography. The colored plate (see Plate XLIV) will indicate with reliable accuracy the relations of the motor centres to each other and to the principal fissures and convolutions. It pertains merely to the left hemisphere of the brain, in whose third frontal convolution is placed Broca’s centre for speech, the corresponding area upon the right side having no exactly corresponding function. The centre for vision, it will be seen, is located in the cuneus, the most basal portions of the hemispheres being the seat of the special senses of taste, smell, and hearing.

Operation.

—The word trephine is at present used both as a noun and as a verb, the older term trepan being now wellnigh discarded. The instrument consists of a section of a tube, one of whose extremities is arranged with sharply cut saw teeth, the whole provided with a grip or handle, which revolves in a plane parallel to that in which the saw teeth cut. The best instrument is that arranged in a slightly conical manner, so that it may less easily burst through the skull and do harm to parts within. The trephine proper is manipulated by the hand. A variety of substitutes have resulted from applications of human ingenuity to the problem of opening the cranial bones. Some of these are operated by foot or hand power, with reduplicated mechanisms, and others by electricity. The more complicated the mechanism the more likely it is to get out of order, and there are but few of these substitutes which give anything like lasting satisfaction.

The operation of trephining is made to include any method by which an opening is made in the uninjured cranium or by which an opening already existing is enlarged and made to subserve the surgeon’s purpose. Aside from the saws already alluded to, there are in use a variety of cutting bone forceps, rongeurs of various device, and a variety of chisels, which are to be used in connection with the mallet or hammer. In order to use any of the latter instruments to advantage the first attack should be made with a trephine of reasonable size, say 2 to 3 Cm. in diameter, after which forceps, chisel, or saw may be used. Straight saws also are of occasional usefulness. I do not favor the use of the chisel and mallet, feeling that the concussions resulting from blows of the hammer add to the shock of the operation. The common trephine is provided with a centre pin, which can be withdrawn after a shallow groove has been cut. To prevent slipping of the centre pin the point to which it is to be applied should be marked by cutting a nick with the point of a chisel.

The Gigli saw should be in every surgeon’s outfit. It consists of a piece of steel wire having a thread cut around and along it by a die, by which it is made as effective as a series of saw teeth. Two small trephine openings are made, and it is then passed into one and out of the other, the dura protected by depressing it, and the wire then handled as though it were a chain saw. It can thus be made to cut its way quickly through the bones of the skull.

Other aids in mechanical procedures are revolving small saws and the surgical engine.

In the absence of a wound a flap of scalp is raised before applying the instrument. This flap is ordinarily of horseshoe shape, and should be made with its convexity pointing toward the occiput, as drainage is best afforded later by this arrangement. The old crucial incisions are now wellnigh abandoned. The pericranium is detached, after incision, with the periosteum elevator, and it should be turned up with its overlying scalp without completely separating it. The scalp flap can be held out of the way by temporarily sewing it to some other part of the scalp, every portion of which should be previously shaved closely and thoroughly scrubbed. The operator has his choice—to seize vessels as they bleed or to make the operation in large degree bloodless by applying an elastic tourniquet tightly around the scalp above the eyebrows and beneath the occiput, the ears preventing it from sliding. If the tourniquet be used the vessels will often bleed in an annoying way after the wound is closed. If the operation be performed for fracture of the skull, should there be an opening already made by the depression of fragments, it may not be necessary to use the trephine, but with suitable bone forceps fragments may be removed or detached. In this case, however, there are often sharp points of bone which will require removal by cutting bone forceps, for the surgeon should leave the margin of the bone opening comfortably round and smooth. Should there be no opening into which the point of an elevator or of bone forceps can be inserted, then one should be made; it is for this purpose that the trephine is mainly used in cases of fracture of the skull. It should now be applied upon a firm and undetached surface of bone, one which will bear the pressure necessary in the process of perforation. As used for this purpose it should be so applied that at least two-thirds of the circle cut by its teeth will be upon unbroken skull; the remaining segment of the circle may be over the fractured area. After it has begun to cut a distinct groove the centre pin should be withdrawn and the instrument maintained in its position during its work by a firm and steady hand, which will force it evenly through the bone and not exercise undue pressure. As the diploë is perforated the bone-dust becomes soft and bloody and the resistance is diminished. As the instrument sinks deeper the operator should frequently intermit its use, and determine his position by means of the irrigator and of the probe or other instrument. The nearer the inner surface is approached the more caution must be exercised, remembering that the bone is likely to be of unequal thickness. When the skull has been completely perforated at one or two points around the little circle the operator should introduce the point of an elevator and pry up the disk of bone, or by rocking the handle of the trephine he may be able to remove the button with that instrument. When the operation is performed in the ideal manner the dura is scarcely touched, certainly not raggedly injured by the teeth of the instrument (Figs. 386, 387 and 388).

Before opening the dura every loose particle of bone and every splinter should be removed, depressed fragments should be picked out, and those which are semidetached should be raised to their proper level. Through the opening thus made the dura is carefully examined; extradural collections of blood are recognized instantly, while some idea as to the amount of intracranial tension may be secured, even through a small opening. Absence of pulsation means probably the presence of cyst, tumor, or abscess deeper. Edema of the membranes usually subsides after nicking or opening them. A yellowish discoloration of the dura often indicates the existence of a tumor beneath. Nothing abnormal being discovered outside of the dura, should brain tension be great or should the dura be discolored, as by blood beneath, the membrane should be opened, by a triangular or horseshoe flap, and the subdural condition accurately estimated. In some cases of meningeal hemorrhage clots will be ejected with some force the instant the dura is opened. In other cases of intracranial pressure, either from tumor or from intraventricular hemorrhage, the brain will instantly protrude to such an extent as to make its reposition difficult or even impossible. Horsley’s dural separator is exceedingly useful, both outside and inside the dura, for detecting and separating adhesions, and as a retractor.

Incisions in the dura should be made, so far as possible, parallel with its vessels rather than across them. When accessible, dural vessels can always be secured and tied. Vessels of the pia can also be picked up and secured with fine catgut ligatures. When the brain tissue itself is diseased it should be carefully excised. The cortex itself is not so vascular as to afford much trouble. Upon any portion of the membranes or cerebral surface a sterilized solution of adrenalin can be sprayed or applied without hesitation. In all deliberate operations sinuses are avoided. When exposed or when necessary to attack them they may be ligated and divided, or may be packed with tampons of sterilized gauze, or may be seized with serrefines or light hemostatic forceps, which may be left for a day or two included within the dressings.

Any of the exposed motor areas or centres can be stimulated, when desired, if the patient be not too deeply anesthetized, by the faradic current of mild degree, applied to surfaces which have not been bathed with antiseptics, nor long exposed to the vapor of the anesthetic, through a double brain electrode made for the purpose, or by sterilized probes connected with the battery.

Buttons of bone or chips of the skull may be replaced after suture of the dura, when desired, though this is seldom advisable. When fragments are thus to be replaced they should be placed in warm sterile salt solution at once after removal, and kept warm. When a button is thus put back the periosteum may be sewed over it with buried catgut sutures.

The dura should be stitched with fine catgut as closely as possible. I have often placed beneath the dural opening a piece of gold, silver, or aluminum-foil, carefully sterilized, with a view to preventing dense adhesions between the dura and the membrane or cortex beneath. I have never known it to do harm.

Drains and drainage are to be avoided when possible, and should be removed early, except in cases of abscess. They may be made of catgut, horse-hair, gauze, rubber, or even of glass, like those short ones which Kocher inserts after extensive operations, their outer ends flanged to prevent their slipping beyond control.

Opening the skull, or, in general terms, trephining, is at present resorted to for the following purposes:

1. For relief of compression—

• (a) By depressed bone, as in comminuted or gunshot fracture;
• (b) By removal of clot or ligation of vessels;
• (c) By evacuation of pus, either from the meningeal cavity or from a deeper abscess;
• (d) By the removal of serous effusions, either extraventricular or intraventricular.

2. For removal of foreign bodies.

3. For relief of intracranial irritation—e. g., epilepsy, the psychoses, etc.

4. For removal of tumors.

5. To compensate for defective development.

6. For exploratory or purely empirical reasons, including the making of “relief openings” for relief of pain, etc.

Aside from the ordinary methods of trephining as applied for common conditions, modern surgery comprises the resort to essentially new methods for raising areas of skull of considerable size and then restoring them to their previous position. These are ordinarily spoken of as osteoplastic resections, and have added very materially to the art and resources of the surgeon. These consist, in a general way, of the formation of a window, as it were, in the vertex or lateral region of the skull by outlining a quadrangular or horseshoe flap of scalp, which is detached only for a slight distance around the incision, after which, by use of the revolving saw or by chisel and mallet, a groove is cut through the bone running parallel with the margin of the scalp-flap, but perhaps a centimeter within it. After this bone area is completely cut through on three sides it is then sprung up or elevated in such a way as to be broken across the base of the bone-flap. It is not at all detached nor separated from the scalp, and so when subsequently lowered into position retains its vitality by virtue of its vascular connections.

When some particular measure seems indicated in order to atone for a large defect in bone it has become quite customary to insert some artificial substitute, mainly either celluloid or a thin aluminum plate, previously absolutely sterilized and cut at the time into such shape as may be called for, but a trifle larger than the real defect, being let in or sprung in, as it were, either completely beneath the bone or into the bony opening, so as not to be easily detached or slip out of the way. By this heteroplastic method most admirable results have been achieved. I have used celluloid for this purpose in the spinal column also, closing with it the defect which remained after the extirpation of the sac of a spina bifida. It is rarely necessary to resort to this practice in the skull, as dense fibrous tissue in due time firmly protects the endocranial contents from external harm (Figs. 386, 387, 388 and 389).