Of the Operation of the TREPAN.

THE Operation of the Trepan, is the making one or more Orifices, through the Scull, to admit an Instrument for raising any Pieces of Bone, that by Violence are beaten inwards upon the Brain; or to give issue to Blood or Matter, lodged in any part within the Cranium.

Fractures of the Skull are at all times very dangerous, not in consequence of the Injury done to the Cranium itself, but as the Brain becomes affected either from the Pressure of the fractured Bone, or that of the extravasated Blood and Matter. If then the Symptoms excited by a Fracture, do sometimes follow from a mere Extravasation of Blood, as is the Case when the Cranium is not beaten inwards, it must likewise happen that a Rupture of the Vessels of this Part, without a Fracture, will also occasion the same Disorders: For this reason, the Operation may take place, where the Scull is not much offended, but only the Vessels of the Dura Mater, the Pia Mater, or the Brain.

The Writers on this Operation, have described the different Disorders in which it is useful, under a great Variety of Names; but those few general ones, which all Surgeons are acquainted with, are quite sufficient for the understanding the Nature of every Case that can happen.

When the Cranium is beaten inward, without any Fracture, it is called a Depression; when very much broken, a Fracture; or if broken and beaten in also, a Fracture with Depression; if it is only cracked, without Depression, though properly a Fracture, it is called a Fissure; if none of these Disorders appear, where there is a Suspicion of them, the Symptoms are imputed to a Concussion of the Brain. These are the four Distinctions in use, and which fully comprehend all the others.

The Depression of the Cranium without a Fracture can but seldom occur, and then it happens to Children whose Bones are more pliable and soft than those of Adults: I have met with one Instance of this myself in a Girl of seven Years of Age: when she first received the Injury, she had the Complaints of an oppressed Brain, but they soon went off; the Blow formed a large Tumour on the Parietal Bone, for which she was put under my Care some Days after the Accident; I opened immediately into it, by cutting away a circular piece of the Scalp, and took out a great Quantity of grumous Blood lying underneath the Periosteum; I then dressed the Depression with dry Lint, and finding no Complaints come on, continued the same Method, 'till in about six Weeks She was perfectly cured.

In Blows of the Cranium, requiring the use of the Trepan, the Marks of a Fracture are generally very evident, since the Scalp is often lacerated so much, as to expose it to our Sight: But if the Wound of the Scalp be so small, as only to admit a Probe, We must judge then by the Feel of the Surface of the Bone, using the Caution of not mistaking a Suture for a Fracture, which Hippocrates confesses he himself did; tho' for his frank Confession of an Error, to prevent others being misled, he is as much recommended to Posterity, as for any of his other Qualities.

If there be no Wound of the Scalp, you must press about the Head with your Fingers, 'till the Patient complains of some particular Part, which in all likelihood is the place affected, and if the Scalp there be separated from the Cranium, is almost infallibly so: The Symptoms of a Fracture are, a Bleeding at the Ears and Nose, a Loss of Sense, Vomitings, Drowsiness, Delirium, Incontinence of Urine and Excrement; but what is most to be depended upon, is a Depression of the Bone, or a Roughness on its Outside; for all the other Complaints, not only happen to Concussions, which do well without the Application of a Trepan, but likewise there are Fractures not attended with any of them, or at least in a slight degree; so that these Symptoms alone, without Examination of the Part affected, are but an uncertain Rule to go by.

In Concussions without a Fracture, that produce the Symptoms here laid down, and do well afterwards, the Vessels of the Brain and Membranes are only inflamed and dilated; or if they are ruptured, they absorb the extravasated Blood again; on which account, Nature should be assisted by plentiful Bleedings, Clysters and other Evacuations, and so in all Fractures where the Patient is not trepanned immediately; however, although People with Concussions in the violent Degree I have stated, do sometimes recover, it is so very seldom, that there can be no Pretence, when they happen, for neglecting the Trepan, but not being able to learn in what Part the Concussion is. The Opportunities I have had of opening some People who have died under this Circumstance, have sufficiently convinced me how little is to be trusted to any other Method than an Opening for the Discharge of the Abscess, which by Confinement of the Matter becomes very large, spreading over a great Quantity of the Brain before it kills.

Writers dispute very much about the Possibility of the Contra Fissure, or a Fissure occasioned on the Part of the Head opposite to that on which the Blow is given, or where the inner Table is fractured, while the outer one remains intire; but there are Histories of Cases, which if fairly stated, make it unquestionable; and this is most certain, that if the Complaint be at a Distance from where the Blow was received, there can be no Danger in Scalping, and applying the Trepan to that Part where the Pain is.

There are Surgeons, who say that the Vessels of the Diploe do sometimes by Concussion break, and that the Matter making its Way through the inner Table of the Scull into the Brain, requires the Trepan; but I believe there is no very good Authority for this Assertion.

When we are assured of a Fracture or Depression though the Symptoms in a great measure go off, and notwithstanding there are a few Histories in Authors, where we read, that Patients have survived without the Operation, it is in my Opinion always adviseable to trepan as soon as possible, in order to prevent the spreading of the Abscess, which seldom fails to follow upon the Rupture of the Vessels of the Brain and Membranes, and for the most part in a few Days; tho' there are a great many Instances of Fractures, not bringing on a fatal Abscess, for a great length of Time after the Accident.

I once trepanned a young Woman about a hundred Days after she received the Blow; the lower Part of the Parietal, and upper Part of the Temporal Bones, were fractured and depressed; she bled at the Nose and Ears when she first received the Injury, and had at times been drousy, and in some little Pain, 'till the towards the ninetieth Day, when the Symptoms of a compressed Brain came on stronger, and a small time after, she put herself under my Care; which, with the many Instances of the same kind to be met with in Authors, shew how little safe it is, to trust to any Extravasation or Depression on the Brain doing well, without the Assistance of the Trepan.

The Manner of treating a Fracture of the Cranium, will be according to the Nature of the Fracture itself, and the Injury of the Scalp; if the Wound of the Head be torn into Angles perhaps cutting off the lacerated Flaps will make room for the Saw; if the Bone be broken into several Pieces, the Pieces may be taken away with the Forceps; or if some of the Scull be also depressed, the removal of the Pieces will, without perforating, make way for the Elevator to raise the depressed part; but if the Fracture be not complicated with a Wound of the Scalp, or the Wound be too small to admit of the Operation, which seldom fails to be the Case, then the Fracture must be laid bare, by taking away a large Piece of the Scalp. It is a fashion with some Surgeons, to make a crucial Incision for this Purpose, which they prefer to the other Method, upon the Supposition that the Wound will more easily heal again after the Operation, by turning down the Flaps; and in case we find no Fracture, which sometirnes happens after scalping, that by making this species of Wound, an Exfoliation of the Bone and tediousness of Cure will be avoided. But whoever has seen the Practice of the crucial Incision, must be sensible of the false Reasoning used in its favour; for it seldom happens that we inquire for a Fracture of the Scull by scalping, but that the Scalp itself is contused, which Circumstance generally bringing on a plentiful Suppuration, and the Matter lodging between the Cranium and Skin, not only prevent their immediate healing, but occasion a Caries of the Bone, which is the Accident meant to be shunned by it; and frequently at last, the Lips of the Wound growing callous, require cutting off, to procure a Cicatrix. If then the Objection be good, to the crucial Incision, when no Operation is performed, it becomes of so much more force when we are assured of using the Trepan, that I think it is indisputably right at all times, to take off the Scalp when we lay bare the Cranium with a view to the Operation, which seldom fails to granulate with Flesh in a few Days, if dressed only with dry Lint, and rarely grows carious, if not affected by a great Discharge of Matter from the Brain, and even in that Case but superficially; or if after it is thus exposed, new Flesh should not generate upon its Surface, the Growth of it may be quickened by boring little Orifices into the Substance of the Bone, or rasping it with the Rugine. The form of the piece taken away may be nearly circular, and to be better assured of the course of the Fracture, it will be proper it should be of the whole length of it. I believe there are few will care to expose so much naked Scull, but whoever knows the great Advantage and the little Danger of it, will not hesitate. When the Scalp is removed, the Periosteum must be raised, and the Arteries immediately tied, which will make way for the Operation to be directly performed; though the Effusion of Blood has been esteemed so troublesome in this Part, as to have made it almost an universal Practice to postpone the use of the Trepan to the Day after; but the Apprehension is without foundation; for if two or three of the larger Vessels are tied, the others may easily be stopped with a little dry Lint, and the Operation take place without any Inconvenience, which I have always done myself, and would recommend to others, considering how urgent the nature of the Distemper is, and that less than twenty-four Hours is often the Difference between Life and Death, when the Brain is much pressed by a fractured Bone.

Before the Application of the Trepan, it is to be remembered there are certain Places on the Scull, where it cannot be used with so much Safety as on others; the whole length of the Sagittal Suture, down to the Nose, is always mentioned as one where the Perforation is dangerous, because of the Spine of the Os Frontis, and the course of the superior longitudinal Sinus under this Part, which it is supposed would be necessarily wounded by the Saw, and in confequence destroy the Patient by the Hæmorrhage; but though a Perforation may, contrary to the general Opinion, be made over the Sinus without offending it, and even if it was wounded, the Effusion of Blood would not in all probability be mortal, (as I have seen in two Instances,) yet at best it Would be very troublesome; and since we are not straitened in that part of the Cranium for room, I think it is adviseable to forbear operating in this Place. The bony Sinuses of the Os Frontis, forbid the use of the Trepan near the Orbits of the Eyes; therefore if it should be depressed near those Cavities, the Surgeon must be careful to perforate either above, or on one side of the Fracture; for sawing below it will only lead into the Sinus, and answer no Purpose in the design either of giving a Discharge to the Matter from the Brain, or an opportunity to elevate the Depression; Nay, perhaps leave an incurable Fistula, If the Patient escapes with Life.

The Os Occipitis being very uneven, both in its internal and external Surface, makes Trepanning there almost impracticable; besides, the great Sinuses run about so much of it, as hardly to afford space to perforate without danger of wounding them; but then it is so defended from Injuries by its Situation and Strength, that Fractures do not happen to it so often as to the other Bones of the Cranium; and when they do, for the most part, they become so soon mortal, by affecting the Cerebellum which it sustains, that the Operation is seldom required in this case. Indeed the upper Angle of this Bone lies above the Cerebellum, and when fractured or depressed is not attended with so immediate Danger; but when this happens, the course of the longitudinal Sinus down the middle of it, and the neighbourhood of the lateral Sinuses beneath it, make it adviseable to trepan at the lower part of the Os Parietale, or at least Upon or just below the Lamdoidal Suture, so that the Perforation of the Os Occipitis can hardly ever be proper.

It may be observed I have spoken of Wounds of the Cerebellum as proving inevitably mortal, when affected by a Fracture: How long a Patient may continue with Matter on its Surface, I cannot take upon me to say, but I believe there is no Instance of a Cure after an Abscess; and as for Wounds of it, they are generally almost instantaneous Death; whereas sometimes great Portions of the Cerebrum have been carried off, or destroyed, without any notable Inconvenience. From this great Difference of Danger, in Affections of the Cerebrum and Cerebellum, has arisen the Opinion, that the first is the Organ of Animal Motion only, and the other of Vital.

The Places then unfit to admit the Saw, are the three I have described; that is, the Sagittal Suture; that Part of the Os Frontis near the Orbits of the Eyes; and the Os Occipitis. But when a Fracture happens in any other part above the Ear, there is no 0bjection to the Operation. When there is only a small Fissure without any Depression or Motion in the Bone, the Trepan may be applied on the Fissure itself, which will more readily give vent to the Blood or Matter underneath, than if made at a distance. If the Fissure be large, and the Bone weakened or depressed, the Trepan must be applied on one side of it, but so as to make it a Part of the Circumference of the sawed Piece; if the Fracture run upwards, it will be eligible always to perforate near its bottom, because the dependency of the Orifice will give better Issue to the Matter, though the ill-grounded Apprehension of the Brain falling Out there, has made many eminent Surgeons contradict this Rule in their Practice. If by making one Orifice, you cannot raise all the depressed part, you must make a second and a third, and continue doing so, till you have reduced the whole Cranium even: there is frequently occasion to repeat it twice or thrice, and it has been done twelve times, nay oftener, with Success, which I mention, to shew the little danger there is, either in sawing the Scull, or exposing the Dura Mater and Brain, when the Pressure is taken off. Indeed the mischief of laying the Brain bare is so small, compared with a Concussion of it, or an Abscess from pent-up Matter, that those Fractures of the Scull, where the Bone is broken into Splinters the whole extent of it, and can be taken away, much more readily do well, than a simple Fissure only, where the Abscess cannot discharge itself freely; for which reason, though the depressed Fracture may be raised by the means of one Orifice, yet if it is of a considerable length, it will be almost absolutely necessary to make one or two more Openings, for the convenience of Discharge; since for want of this, we see Abscesses increase daily in their quantity of Matter, and at the end of a few Weeks, carry off the Patient. Those that are conversant in the Dissection of Persons dying of this Disorder, will be convinced of the force of this Reasoning, since they not only constantly find Pus lodged on the Brain, as far as the Fissure extends, but all round about it, sometimes spreading over a quarter of its Surface.

In Concussions of the Brain without a Fracture of the Cranium, if the Trepan be applied, and vast Discharges ensue, it will be also convenient to make more Perforations into the Abscess and the neighbourhood of the Abscess, the Situation of which will be easily guessed by the direction of the stream of Matter. And here it is to be observed, that Abscesses which ensue from a Concussion, are generally more extensive and dangerous, than those which accompany a Fracture with Depression; for in a Fracture, the yielding of the Bone destroys, in a great degree, the Force of the striking Body, and prevents any violent Commotion of the Brain; so that what the Brain suffers, results chiefly from the Pressure of the incumbent Bone, and the Laceration of the Vessels, near the Fracture; whereas when the Cranium resists the Shock, all, or great Part of the Cerebrum sustains the Concussion, and is often impostumated or inflamed almost in its whole Dimension, as we find upon opening those who die of this Disorder.

The Manner of Trepanning is this: Having fixed your Patient's Head steady, either on the Bolster of a Bed, or by placing him in a low Chair; with the Pin of your Saw, mark the Center of the Piece of Bone to be taken out; then with the Perforating Trepan, make an Orifice deep enough to receive the Pin, which being fixed in it, will prevent the Saw from slipping; and thus you are to continue sawing, 'till the lmpression made will preserve the Steadiness without the Pin, when it is to be taken away, for fear of its wounding the Brain before the Saw has entered through the Cranium, which it would do at last, because of Its Projection. In working through the Bone, the Teeth of the Saw will begin to clog, by that time you arrive to the Diploe, wherefore a Brush must be ready to clean it every now and then, and with a pointed Probe you must clear away the Dust in the Circle of the trepanned Bone, observing if it be deeper on one Side than the other, to lean afterwards on that Side where the Impression is least, that the whole thickness may be sawed thro' at the same time. To do all this with less Interruption, it will be proper to have two Saws of exactly the same Diameter, that an Assistant may be brushing one while you operate with the other. We are advised to saw boldly, 'till we come to the Diploe, which it is said, will always distinguish itself by the Bloodiness; but, however this is not a certain Mark to go by; for tho' where there is a Diploe, it will manifest itself by its Bloodiness, yet sometimes the Scull is so very thin as not to admit of any; in which case, if an Operator should push on his Instrument in expectation of meeting with this Substance, he would unwarily wound the Brain. This is not very often the case, but however often enough to put a Man on his guard, and make him enquire whether the Bone be loose after a little sawing, which is the only Rule we go by when we have passed thro' the Diploe, and may as well be attended to, before coming at it, without any considerable loss of Time. When it is quite sawed through and lies loose, it may be taken away with the Forceps, contrived for that Use; and if the lower Edges of the Orifice, next to the Dura Mater, are splintered, they may be scraped smooth with a Lenticular.

These are the chief Processes of the Operation of the Trepan; the only thing remaining to be done, is with an Elevator introduced at the Orifice to raise the Depression, or broken Splinters, if they cannot otherwise be laid hold of, and to draw out the grumous Blood, or any other extraneous Body. If the Dura Mater be not wounded or torn, an Incision must be made thro' it, to give way to the Blood or Matter, which almost certainly lie underneath it, if the Symptoms have been bad, and none has been discharged from between the Cranium and Dura Mater: Though it has been lately observed that an Abscess will sometimes be formed, in the Substance of the Brain; and therefore if the Puncture of the Dura Mater does not procure an Evacuation of the Matter, and the Symptoms of a Suppuration are still urgent, it will be adviseable to make a small Incision with a Lancet into the Brain itself.

I have used the Word Trepan all along, for the sake of being better understood; but the Instrument I recommend is a Trephine, the Advantages of which, as also that of a cylindrical Saw, or one nearly cylindrical, are described in the Explanation of the Copper-Plate.

With regard to the Dressings of these Wounds, I think it is very certain, that as the greatest part of the Evil proceeds from the Quantity and Pressure of the Matter, whatever approaches towards the Nature of a Tent, and increases its Quantity and Pressure, by locking it up, must be pernicious: Therefore, I would exclude the use of all Syndons whatever; the hasty Application too of Spirits of Wine, which is so commonly advised, cannot be proper; as they are not only unfit for Inflammations in general, but also crisp up the Vessels of the Dura Mater and Brain, and stopping the Suppuration, sometimes produce a Gangrene. Since then a close Application is inconvenient, and whatever good there may be in Topical Medicines, it cannot for the most part be communicated to the Abscess, by reason of its extent beyond the Orifice. The best Remedy will be dry Lint only, which must be laid on loosely to give vent to the Matter, and be repeated twice a-day 'till the Discharge is lessened, when once in twenty-four Hours will be sufficient to the finishing of the Cure, which will be something retarded by the Exfoliations that sometimes follow this Operation. The Patient afterwards may wear a Plate of Tin upon the Scar to defend it from Blows or any accidental Injury.



A. The Perforator, commonly called the Perforating Trepan. With this Instrument, an Orifice is usually made for the Reception of the Pin, on the Center of the Piece of Bone that is to be taken away, in the Operation of Trepanning; though if the Pin be very sharp, and project but little beyond the Teeth of the Saw, as in that marked with the Letter B, the Perforator would be needless; but as the Point of the Pin presently grows blunt with Use, and in that case, it is difficult to fix the Saw, I think it adviseable to have this Instrument in readiness. It is also handy for boring into the Substance of the Bones, in order to promote a Granulation of Flesh on their Surfaces: When it is made use of it must be received and fastened in the Handle C.

B. The Crown, or Saw of the Trepan, with the Pin appearing just beyond the Extremities of the Teeth. It may be observed, the Shape of this Saw is cylindrical, differing from those in use which are all Conical, and some, in a very great Degree. Surgeons have generally conceived great Advantages to arise from this Form: First, as a Circumstance of the utmost Importance, they have imagined there would be danger of injuring the Brain, by sawing too suddenly through the Cranium, if the Enlargement of the Saw did not increase the Obstruction, in proportion as they advanced towards it, and make the working of the Instrument exceedingly slow. It has also been believed, that unless the Saw was smaller near the Teeth, than towards its Basis, it would be impossible to incline it on any part where it had not made so deep an Impression as in others, in consequence of which, one side of the Circle would be sawed through, and the Membranes or Brain injured, while on the other, perhaps the Saw would not have penetrated through the first Table of the Cranium: The last remarkable Argument in favour of the Conic Saw is, that it more readily admits, and afterwards retains the sawed piece of Bone in its Cavity: But I think all the Advantages attributed to this Figure are almost imaginary; and the great Labour of working so slowly and difficultly, is not only very inconvenient to an Operator, but by no means serviceable to the Operation; for notwithstanding the Saw be Cylindrical, and works without any other Impediment than what lies before the Teeth, yet even with this Advantage, the Operation goes on so gradually, that from the Experience I have had; I do not find the least danger of suddenly passing through to the Brain as is apprehended, if we proceed with the Caution of not leaning too hard on the Instrument when the Bone is almost sawed through; and with respect to the Impracticableness of inclining it on any particular part of the Circle, when sawed uneven, which is commonly alledged, whoever will try the Experiment, will in a Moment discover the Falseness of the Assertion; besides, the very Instance stated overthrows this reasoning, for if the Circle has been already made deeper in one part than another, it must imply that we have leaned with more Force on one part than another, and consequently may at pleasure do the same thing again: As to the last supposed Advantage, of its receiving and retaining the sawed piece of Bone in its Cavity, the Benefit would be so frivolous, if it had truly the Preference of the Cylindrical one in that respect, that it would not be worth mentioning; but in fact, the Cylindrical Saw receives the piece of Bone very readily, and often retains it in its Cavity.

C. The Handle of the foregoing Instrument, called the Trephine, which is much preferable to the Trepan, (an Instrument like a Wimble used by joiners) because of the great Convenience of holding it, and leaning on one side or other of the Saw, as we find it necessary: The Trepan however, though allowed to be unhandy, is the Instrument most used by Surgeons in other Parts of Europe, upon the Supposition of its working quicker than the Trephine.

I have represented the Trephine of such a Shape as to make it a convenient Elevator, for which purpose the Extremities of it are made rough.

D. A Key to take out the Pin E, when the Saw has made an Impression deep enough to be worked without the help of it.

E. The Pin.



A. A convenient Forceps to take out the circular piece of Bone, when it does not stick to the Saw: the Contrivance by which they readily lay hold of it, is to make the Extremities that are to grasp it, with an Arch of the same Circle as the Saw is made. Upon one of the Handles, there is added a little Elevator, to lift up any small Splinter of Bone, but it is not of much use.

B. A Lenticular: the forepart of its Blade is sharp, in order to scrape the lower Edge of the Orifice of the Cranium, in case any Splinters should remain after the Operation, and the Button at its Extremity receives the Dust, that it may not fall on the Brain; but there is seldom any Occasion for this Instrument, and I have never myself been under the Necessity of using it.

C. A Rugine, or Raspatory, which I have recommended for scraping Bones, in order to promote Granulations of Flesh. The Handles of these two last Instruments are Wood, whereas every Part of the others should be made of Steel.

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