CHAPTER V

OPERATIONS UPON THE MASTOID PROCESS: WILDE’S INCISION AND SCHWARTZE’S OPERATION

With few exceptions the conditions requiring operative procedures on the mastoid process are the result of some suppurative lesion which has originated within the tympanic cavity.

The object of such operations is to arrest or eradicate the disease which, by further extension through the bony walls of the temporal bone, might eventually cause death by giving rise to some suppurative intracranial complication.

For their successful performance a knowledge of the anatomical relationships of the mastoid process is essential. It is sufficient here to remind the reader of the main surgical points in this connexion (Fig. 215).

SURGICAL ANATOMY OF THE MASTOID AREA

=The mastoid antrum.= At birth the mastoid antrum is almost fully developed. In infancy it is situated superficially and at a much higher level in relation to the auditory canal than in the adult. In the infant, also, the petro-squamous and the squamo-mastoid suture are still patent. As the mastoid cells develop, the antrum gradually becomes more deeply placed, so that in the adult it is from half to three-quarters of an inch from the surface.

Its roof, the tegmen tympani, is continuous with that of the attic. Anteriorly it is separated from the external auditory meatus by the posterior wall of the auditory canal, whose innermost margin forms the outer wall of the aditus. On its inner wall lie the semicircular canals, whilst posteriorly the lateral sinus is separated from it by an intervening layer of mastoid cells or compact bone. Between the semicircular canals and the lateral sinus is a small area composed of a thin layer of bone, separating the antrum from the posterior fossa of the cranial cavity.

=The mastoid process.= In the infant this is undeveloped and is merely represented by a small bony protuberance. By the fourth year it has practically reached the adult type.

Anatomically the mastoid process can be subdivided into three chief types: (1) the pneumatic, in which the cells are few and large; (2) the diploic, containing numerous small cells; and (3) the compact, in which the bone is extremely dense. Mixed types are frequently found, the cortex, as a rule, being more dense than the deeper portion. Occasionally it is uniformly sclerosed, almost of the consistence of ivory, but in these cases the condition is usually pathological, the result of chronic inflammation of the mastoid process.

The mastoid cells converge towards the antrum and may be divided into two groups: (1) those extending vertically downwards to the tip of the mastoid process; and (2) those lying between the antrum and the sigmoid process of the lateral sinus. In addition to these two groups, it must not be forgotten that cells may extend in other directions; for instance, (_a_) anteriorly, along the root of the zygoma; (_b_) posteriorly, communicating with the cells of the occipital bone; (_c_) inferiorly, between the floor of the tympanic cavity and the jugular fossa; (_d_) internally, spreading inwards towards the apex of the petrous bone and surrounding the labyrinth; or (_e_) enveloping the orifice of the Eustachian tube.

_The facial nerve_, after dipping beneath the external semicircular canal, passes vertically downwards through the mastoid process to emerge at the stylo-mastoid foramen. Entering this foramen and running along the canal are the stylo-mastoid branches of the posterior auricular artery. These vessels, if cut through by the chisel, may bleed in a marked manner, thus drawing the attention of the operator to the fact that he is in close proximity to the facial canal and nerve.

=Surface anatomy.= Although it is impossible to foretell with certainty before operation what the anatomical structure of the mastoid process may be, yet some information may be gathered from the formation of the skull.

In the dolichocephalic type, the mastoid process is broad and frequently contains large cells, especially at its tip and round the lateral sinus, which is usually deeply placed. In the brachycephalic type, on the other hand, there is a greater tendency for the mastoid process to be narrow and to consist of dense bone, for the middle fossa to extend low down and to overlap the outer wall of the antrum, and for the lateral sinus to project forward and superficially, even to within 2 or 3 millimetres of the posterior border of the external meatus.

The posterior root of the zygoma may be considered approximately the line of demarcation between the roof of the antrum and mastoid process, and the floor of the middle fossa of the skull. This, however, is only a rough guide, as in some cases, especially of the brachycephalic type, the middle fossa may dip below this point. If this ridge is not well marked, then Reid’s base-line must be taken as the guide.

Just behind the auditory meatus, at its upper posterior margin, is the spine of Henle, which forms the anterior boundary of the suprameatal triangle. Macewen, who first described this triangle, gave it as a guide for the exposure of the antrum. Experience, however, has shown that no reliance can be placed on this as a landmark, as, if the bone is chiselled through at this point, it is by no means uncommon to expose the dura mater of the middle fossa. A point 10 millimetres (two-fifths of an inch) behind the spine of Henle corresponds to the anterior border of the sigmoid sinus. Behind the suprameatal triangle and beneath the zygomatic ridge is the body of the mastoid process, which has a smooth surface and is perforated by small foramina through which pass tiny vessels.

The antrum, in the adult, is situated at a slightly higher level than the tympanic membrane, its floor roughly corresponding with a line drawn horizontally backwards through the middle of the posterior wall of the bony meatus.

HISTORY OF THE MASTOID OPERATION

Although opening of the mastoid process as an operative measure dates back to the eighteenth century, yet Schwartze, in 1873, was the first to establish the operation as a practical procedure.

Schwartze’s operation consisted in the simple opening of the antrum and mastoid cells, leaving the middle ear untouched. This procedure was carried out no matter whether the disease was recent or long standing. It soon became recognized, however, that this operation did not effect a cure in all cases, more especially in those in which the disease involved the walls of the tympanic cavity.

Küster, in 1889, suggested removal of the posterior wall of the external auditory meatus, and about the same time von Bergmann advocated removal of the outer attic-wall. The Küster-Bergmann operation, first practised by Zaufal, may therefore be considered to be the origin of the complete mastoid operation.

Stacke’s name is frequently though wrongly mentioned in association with the complete operation, which is sometimes termed the Schwartze-Stacke operation. Stacke’s operation was devised with a view to removal of the ossicles and outer wall of the attic in those cases in which the bone disease was limited to these regions. This operation, however, is occasionally of service in the performance of the complete mastoid operation (see p. 397).

Thus the year 1889 may be considered as the starting-point of the complete mastoid operation. Since that date many modifications have been introduced, the majority of which are not worthy of reference.

After the technique of the operation had been developed and practised for some time, more careful attention was directed to the after-treatment. In the earlier days of the radical operation it was the rule to leave the wound open and to plug it with gauze, or to insert a drainage tube which was carried through the membranous portion of the external meatus.

The next step was the making of post-meatal skin flaps, with closure of the posterior incision and packing of the wound through the auditory canal; and the names most prominently associated with this are Panse, Körner, and Stacke.

Still more recently, in order to shorten the after-treatment, the wound cavity has been skin-grafted by the method first suggested by Siebenmann and afterwards amplified by Charles Ballance.

The operations which will be considered are:--

1. Wilde’s incision.

2. Opening of the mastoid process and antrum.

3. The complete or radical mastoid operation.

Although definite indications for the above operations will be given, it must be remembered that in many cases the extent of the operation will depend very largely on the pathological condition found during the course of the operation itself, as frequently the clinical symptoms are not sufficient to determine beforehand what operation is indicated.

In comparing the simple opening of the mastoid cells and antrum with that of the complete or radical operation, the fundamental difference is that in the former the tympanic cavity and its contents are not interfered with, whereas in the complete operation the middle ear, antrum, and mastoid cells are converted into one large cavity. In consequence, complete recovery of hearing may take place in the former case; in the latter, however, this is not possible.

Although these operations, especially in the more acute conditions, are performed from the point of view of saving the life of the patient, due regard must also be given to the preservation or restoration of the hearing power, if this indeed is possible. If the hearing power be very poor, that is, if conversation cannot be heard more than 12 feet off, and especially if the deafness be partially due to changes having already taken place within the labyrinth, then the complete operation is to be preferred if it be doubtful whether Schwartze’s operation will be sufficient to eradicate the disease. If, on the other hand, the hearing power of the affected ear be fairly good, and with this there is deafness of the opposite side, then, unless it is absolutely essential that the complete operation should be performed, an attempt should be made to effect a cure by the simpler operation, provided it is first explained to the patient that it may perhaps be necessary to perform the complete operation afterwards.

WILDE’S INCISION

In cases of acute inflammation of the mastoid process or of a subperiosteal abscess lying over it, Wilde made a post-aural incision, incising the tissues down to the bone. The indications for doing this are now considered to be very few, but it must be remembered that in Wilde’s day the mastoid operation had not been developed.

=Indications.= (i) In infants it is sometimes justifiable, as the pus may have escaped to the surface of the mastoid process either through the squamo-mastoid suture or along the posterior wall of the auditory canal, between the periosteum and bone, without there being any actual disease of the bone.

(ii) As a temporary measure, to permit of drainage of a subperiosteal abscess, if the operation on the mastoid process cannot be performed for twenty-four hours or more.

(iii) In acute middle-ear suppuration a free incision down to the bone may relieve the pain if there are symptoms of periostitis of the mastoid process; it is, however, rarely necessary.

=Contra-indications.= In older children and adults (with the above exceptions) this operation is not sufficient, as the periostitis or subperiosteal abscess over the mastoid process is secondary to underlying bone disease which can only be eradicated by an operation on the mastoid process itself. Although healing may apparently take place, fistulæ or other evidences of mastoid disease almost invariably occur afterwards.

=Operation.= In an infant a general anæsthetic is not necessary, but in an adult gas anæsthesia is advisable. The mastoid region is surgically cleansed; the auricle is pulled forward and a free incision is carried down to the bone, in a curved direction downwards over the mastoid process. Originally Wilde made a vertical incision; but it is better, if possible, that the incision should be the same as would be made in performing the mastoid operation, which indeed will probably have to be carried out afterwards. After the hæmorrhage has ceased and the purulent contents of the abscess, if present, have drained away, fomentations should be applied and changed frequently during the first twenty-four hours. After this a simple dry dressing is sufficient.

=Results.= Except in the case of tiny infants, this procedure is seldom successful in curing the condition, and must be considered as only a temporary measure.

SCHWARTZE’S OPERATION

(Opening of the mastoid process and antrum)

=Indications.= (a) _In acute middle-ear suppuration._ (i) If, in spite of free drainage, earache, pyrexia, and tenderness over the _body_ of the mastoid do not abate within three days. This is all the more urgent if the condition is the result of scarlet fever or influenza, as in these cases the disease may spread with extreme rapidity.

(ii) If there be an obvious abscess over the mastoid process; except in infants, in whom Wilde’s incision may be attempted as a tentative measure, although it is not recommended.

(iii) If there be symptoms of meningeal irritation.

(iv) If a profuse otorrhœa has continued for over four weeks and is accompanied by sagging downwards of the upper posterior wall of the external meatus, a definite sign that the antrum is involved.

(v) If a profuse otorrhœa has continued for over eight weeks, with no sign of abatement, even although the temperature may be normal and although there may be no symptoms of inflammation of the mastoid process. The continuance of the otorrhœa is presumably due to accumulation of pus in a large antral cavity. The object of the operation is to permit of free drainage and to prevent involvement of the mastoid process itself. The question of operation, however, must be considered very carefully. There is no doubt that in many cases conservative measures may effect a cure even although the suppuration has already existed for many months.

(_b_) _In chronic middle-ear suppuration._ Although the complete mastoid operation is usually indicated, yet the simple opening of the mastoid antrum may be advised under the following conditions, provided there are no symptoms of inflammation of the mastoid process nor signs of disease of the bony walls of the tympanic cavity:--

(i) If the perforation, however large, be surrounded by a rim of tympanic membrane (showing that there is no disease of its bony margins), and if the malleus be not adherent to the inner wall of the tympanic cavity.

(ii) If the hearing be good, that is, if speech is heard farther off than 12 feet, especially if the other ear (from whatever cause) be quite deaf.

Politzer, among others, still maintains that there is frequently no communication between the affected mastoid cells and the antrum if the mastoid abscess is the result of acute middle-ear suppuration. For this reason he considers that the antral cavity should only be opened if there be definite evidence of bone disease between the abscess cavity and the antrum, or if symptoms of extra-dural abscess or some intracranial complication be present. It is, however, difficult to believe that some communication, however microscopic, does not always exist between the antrum and the mastoid cells, seeing that the latter originally developed as outgrowths from the antrum itself, and must have become infected by direct extension from it. At the same time there is no doubt that complete recovery takes place in a certain number of cases in which the antrum has not been opened.

In my opinion, however, it is always wiser in such cases to open the antrum. Politzer considers that if this be done, healing does not take place so rapidly as in those cases in which the antrum has not been opened. On the other hand, if the antrum be not opened, the main object of the operation, that is, free drainage of the contents of the aural cavity, is not attained.

=Operation.= _Preparation of the patient._ The head should be shaved for a space of 2 inches around the mastoid region, twenty-four hours before the operation if possible. In women the hair in front of the ear, instead of being shaved off, should be combed forward and plastered down with carbolic soap. By doing this the hair can be arranged so as to cover the bald area during convalescence, a matter of great satisfaction to the patient.

The area of the operation and surrounding parts should be thoroughly washed with ethereal soap solution and afterwards protected with a compress of 1 in 2,000 solution of biniodide of mercury. After the patient has been anæsthetized, the cleansing process should be repeated, and the auditory canal syringed out with the lotion. The head is then covered with a sterilized towel drawn tightly over the ear and scalp, a portion of the towel being afterwards cut away so as to expose only the field of operation. The patient should be in the recumbent position, the head resting on some hard substance, such as a partially-filled sand-bag, and turned over to the opposite side, so that the affected ear is uppermost.

In addition to the ordinary instruments, those specially required for this operation are a well-balanced mallet and several gouges and chisels of varying size, one or two sharp spoons, a seeker, and a malleable blunt-pointed silver probe. They should be sterilized in the ordinary manner.

_The incision._ The surgeon stands at the side to be operated upon, facing the patient’s head. The auricle is pulled forward. An incision is made through the skin, beginning just above the pinna, and is carried downwards in a curved direction towards the tip of the mastoid process, lying about half an inch behind the insertion of the auricle (Fig. 216). Before making the incision, the tip of the mastoid process should be determined. Care must be taken not to let the knife slip at the end of the incision and so incise the neck tissues. The line of incision should correspond to what will afterwards be the middle of the wound cavity in the bone. If the incision be made too far forwards or too far backwards, one of the edges of the skin incision may afterwards tend to overlap the opening in the bone and in this way hinder the dressing and perhaps lead to the formation of a sinus. If there be much thickening of the soft tissues and periosteum, it may be necessary to make the incision longer than usual in order to expose the field of operation sufficiently.

In the upper angle of the incision the temporal fascia and the underlying temporal muscle will be exposed. Except in very muscular subjects, in whom the muscle comes low down into the wound and has to be cut through, it is better to push the lower border of the muscle upwards by means of a periosteal elevator. The incision is now carried right down to the bone throughout its length.

If there be an abscess over the mastoid process, its purulent contents should be allowed to drain away, the abscess cavity being then irrigated with a weak solution of biniodide of mercury (see p. 389).

_Exposure of the field of operation._ The periosteum and overlying soft tissues are then reflected forwards and backwards with a rugine, until the following points are brought into view: namely, the upper posterior margin of the bony meatus (taking care not to separate the fibrous from the bony portion of the meatus) and Henle’s spine in front, the zygomatic ridge above, and the fibres of the sterno-mastoid muscle below (Fig. 217). The tip of the mastoid process should just be seen. To do this it may be necessary to cut away some of the fibres of the sterno-mastoid muscle.

If the surgeon has two assistants, the duty of one of them is to hold apart the edges of the wound by means of retractors, whilst the other is employed in keeping the wound dry. If there be only one assistant, the edges of the wound may be held apart by metal retractors.

Careful examination of the field of operation should now be made. There may be no external signs of disease. As a rule, however, as a result of the inflammatory process having already extended to the surface, the periosteum is found to be much thickened, with extreme vascularity of the underlying bone, or there may be a subperiosteal mastoid abscess of varying size.

Excepting in infants, in whom pus may escape through the squamo-mastoid suture, a subperiosteal abscess is always secondary to a fistula in the bone, which is usually situated over the body of the mastoid process just behind the suprameatal triangle. It may, however, occupy some other position.

In the case of Bezold’s mastoid abscess (see p. 389), although no fistula may be seen on the surface of the bone, pus may be found to well up from beneath the mastoid process on cutting through the fibres of the sterno-mastoid muscle. In other cases there may be actual necrosis of the bone, as a rule involving the lower margin of the squamous portion of the temporal bone (see p. 390).

The method of opening the antrum in a straightforward case will first be described.

_Opening the antrum._ The approximate surface marking of the antrum is the suprameatal triangle and the region just behind it, which, however, as has been mentioned, is an uncertain guide. It is wiser, therefore, in all cases of operation on the mastoid process to assume that the case is one in which the lateral sinus extends far forward and is superficial, and that the middle intracranial fossa is low lying.

The area of bone to be removed depends on the age of the patient; in the adult it is about half an inch square, having as its boundaries the zygomatic ridge above and Henle’s spine in front.

The bone should be removed by short decided taps of the mallet on the gouge or chisel, held in contact with the bone in a sloping direction (Fig. 217). This precaution is specially indicated whilst in the act of removing the bone from above downwards and from behind forwards, in order to prevent injury to the middle fossa, which may be low lying, or the lateral sinus, which may project abnormally far forward (Fig. 218).

To permit of better control over the instrument, the hand holding it may rest lightly against the patient’s head, which is now covered with a sterilized towel. This control should always be sufficient to prevent the chisel or gouge being driven unexpectedly too far inwards, an accident which may easily happen if, by chance, there is a sudden diminished resistance to the stroke owing to unexpected softening of the bone or the inadvertent exposure of the dura mater. It is this accidental slipping of the instrument which is often responsible for injury to the lateral sinus or the facial nerve. With regard to choice of instruments, I prefer the gouge, as it is safer than the chisel, owing to it having rounded edges.

On removal of the superficial part of the cortex, the mastoid process may be found to be sclerosed, or to consist of small or large cells filled with granulations or purulent secretion.

(_a_) _If the bone be sclerosed._ The operation may be extremely difficult, as the antrum is frequently of small size and very deeply placed. As the tympanic cavity must not be interfered with, it is not permissible to insert the seeker along the auditory canal into the attic in order to determine the position of the aditus. The only guides, therefore, are the anatomical landmarks.

The best method is to chisel away the bone close to and parallel to the upper posterior margin of the external meatus. In chiselling along the upper wall of the opening, the gouge, instead of being directed downwards, as was the case in removal of the outer portion of the cortex, is now directed inwards and at the same time slightly upwards and forwards. In enlarging the lower part of the opening, the bone is chiselled away obliquely inwards and upwards. The strokes of the gouge are made alternately from above and below, so that gradually a funnel-shaped opening is formed, having its point directed towards the aditus.

Anteriorly, the bone is removed as close to the posterior wall of the auditory canal as possible, including the suprameatal spine. Above, the line of chiselling must not extend beyond the zygomatic ridge, whilst below sufficient bone should be removed towards the tip of the mastoid process to permit of inspection of the deeper parts of the wound.

From time to time the operator makes use of the _seeker_ (Fig. 219). This is a blunt-pointed probe whose tip is bent at right angles to its shaft. With it any opening is probed carefully to see whether it is merely a mastoid cell, or dura mater covering the outer wall of the lateral sinus, or the middle cranial fossa, or if indeed it is the antrum itself. The chief mistake is to work too low down. If the antrum be small it may be missed, and the bone may be chiselled away too deeply in endeavouring to discover it and the facial nerve or the external semicircular canal injured. It is wiser, therefore, to work high even if the dura mater of the middle fossa is exposed by doing so. This should not lead to any harmful result provided the dura mater is not injured.

As soon as the antrum is reached, pus will be seen to ooze through the opening made, especially if it is under tension. The probe or seeker can now be passed into a cavity of varying size. The antrum is recognized by its smooth surface, which has quite a different appearance to that of the mastoid cells.

(_b_) _If the mastoid be not sclerosed._ The pathological condition found on removal of the superficial cortical layer depends on the anatomical structure and on the extent and virulence of the inflammatory process. Only a few cells may be involved, or on the other hand the whole mastoid process, if it be of the pneumatic type, may be converted into a mere shell of bone, forming a large cavity filled with masses of septic granulation tissue, carious bone, and pus. Sometimes, indeed, owing to the tegmen tympani or bony wall of the sigmoid sinus being already destroyed, the dura mater above or the lateral sinus posteriorly may be found already exposed within the cavity. If this is the case the pus may pulsate if present in large quantity. Any patches of soft carious bone or granulation tissue should be removed with the curette.

If the disease be limited to a few superficial mastoid cells, it is sufficient, according to those who do not always explore the antrum, to expose and curette the cavity freely and to do nothing further. This, however, should only be done if the bone surrounding the abscess cavity is hard and apparently normal, and if there is no tract of granulations leading from it in any direction. If an opening be found leading directly into the antrum, it should be enlarged with the curette or gouge. The extent of the antrum is next defined with the seeker, any overlapping ledges of bone being removed by the gouge until the whole of its inner surface is exposed.

The region of the aditus is now inspected under good illumination, using a head-light if necessary. It is recognized as a small opening at the anterior inner part of the antrum, on the floor of which may be seen the posterior border of the external semicircular canal, standing out as a whitish rounded eminence. Bone may be removed from its upper inner margins, but the lower portion should not be interfered with for fear of injuring or displacing the incus. To confirm the opening into the aditus, a blunt-pointed curved probe may be passed for a short distance through the aditus into the attic (Fig. 220).

With the curette all granulations should be removed.

_Treatment of the mastoid process._ The question now arises as to how much bone to remove. This depends on the condition found; the chief point is to make certain of removing all the infected cells.

In the case of marked sclerosis, the opening need not be large because, if the bone between the cortex and the antrum be solid, it is hardly probable that infection can spread through it to any outlying cells in the tip of the mastoid or elsewhere.

In the diploic and pneumatic varieties, the seeker must be used constantly in order to discover any outlying cells, which are then opened freely. If this be done systematically, infected cells may be found some distance away from the antrum itself, although an area of apparently healthy bone lies between them and the antrum. It must not be forgotten that cells may extend posteriorly as far as the occipital bone, or anteriorly along the zygomatic process, or even into the upper posterior part of the auditory canal itself (see p. 374). If such infected cells be not discovered, healing will be prevented.

However small or large the opening may be, all rough corners must be removed, so that at the end of the operation a smooth funnel-shaped cavity exists. To obtain this _a burr_ may be used, worked either by the electric motor or, if a portable one, by an assistant. The burrs are of various sizes and of the cross-cut variety recommended by Ballance. Some operators perform the operation by burring throughout. Personally, during the earlier stages of the operation, I prefer to use the gouge and mallet. If the operator has not had much experience in the use of the burr there is always a slight risk, if it be not kept sufficiently under control, and especially if too great pressure be used, of it being driven through the dura mater above or into the lateral sinus posteriorly, or of it injuring the contents of the tympanic cavity. As a means of finishing the operation no instrument could be better. In private practice, however, few surgeons keep one. For this reason it is advisable to become accustomed to the chisel and gouge.

_Removal of part of the posterior wall of the auditory canal._ This may be necessary if the anterior wall of the antrum and mastoid process be affected. The fibrous portion of the auditory canal is partially separated from the bony portion and held forward by means of a retractor. The upper posterior portion of the bony meatus can now be removed either by means of punch-forceps or by the chisel, to what extent does not matter so long as its innermost portion, ‘the bridge,’ is not interfered with, that is, so long as the tympanic cavity and aditus are not encroached upon.

_Exposure of the dura mater and lateral sinus._ This may have already occurred before the operation, as a result of extension of the bone disease, or it may be necessary to do so during the course of the operation. Owing to the fact that an extra-dural abscess is a frequent complication of acute inflammation of the mastoid process, Victor Horsley and Körner advocate the exposure of the dura mater and the lateral sinus in every case, especially if a tract of carious bone leads in their direction. No harm is done in exposing these structures, and it precludes missing an extra-dural abscess.

It is better to expose the dura mater than to leave it covered with infected bone and septic granulations.

_Final step of the operation._ In order to make certain that a free opening exists between the antrum and the tympanic cavity, some warm boric lotion should be syringed through the opening of the aditus. A small syringe is used, having a fine piece of india-rubber tubing fixed on to its point. The end of the tubing is pushed into the entrance of the aditus. The fluid is then syringed through and should emerge from the external meatus. This is also beneficial in order to cleanse the tympanic cavity of its purulent secretion. To expel all the fluid from the middle ear the syringe is emptied and the piston withdrawn to its full extent. Its point is again placed within the entrance of the aditus and the piston pressed home, so that air is forced through and so drives out any remaining fluid from the tympanic cavity into the external meatus, which in its turn should be carefully dried. If there be no perforation, or if it be very small, the membrane should be freely incised before fluid is syringed through the aditus.

_Immediate treatment of the wound cavity._ The wound cavity is lightly packed with sterilized ribbon gauze, half an inch in width. Care must be taken to introduce the gauze right down to the aditus and to pack the cavity evenly.

The wound should be left open for a few days until the acute inflammation of the soft tissues has subsided, after which the upper and lower angles of the wound can be partially closed by sutures. A strip of gauze is also inserted into the auditory canal and a light dressing of plain sterilized gauze and a pad of cotton-wool covers the ear and surrounding parts. The bandage should be passed round the head and not beneath the chin, as the latter method is often a source of great discomfort to the patient during the stage of vomiting following the anæsthetic.

Blake of America has suggested that the wound should be allowed to fill with blood-clot on the supposition that the subsequent organization of the clot will result in a rapid closure of the wound. This method cannot be considered seriously owing to the impossibility of keeping the wound sterile.

=After-treatment.= There is seldom any shock, but there may be considerable pain during the next twenty-four hours.

If there has been no subperiosteal abscess, the dressing need not be removed for forty-eight hours. If an abscess has been present the dry dressing should be removed after twenty-four hours, and if there is much œdema and inflammation of the surrounding region, a compress of wet boric lint, kept in position by a few turns of a bandage, should be substituted, and changed every four hours.

Drainage tubes should be shortened and removed as soon as possible. The gauze within the wound cavity should be changed every second day, or daily if there be much secretion. If there be much discharge and the condition be very septic, an ear-bath of hydrogen peroxide may be given at each dressing and the cavity syringed out with a weak solution of biniodide of mercury; otherwise it is sufficient to use boric acid lotion.

If the operation has been successful, the purulent discharge from the tympanic cavity rapidly diminishes, frequently ceasing before the third day. The auditory canal is then firmly packed with gauze, especially in its outer part, in order to prevent stenosis of its lumen, which is liable to occur if the posterior fibrous portion of the canal has been separated from the bony meatus during the operation. Granulations very quickly block the aditus and so separate the antrum and mastoid cavity from the tympanic cavity. The wound can now be treated as an ordinary deep surgical wound, care being taken that it is packed from the bottom at each dressing.

If all the diseased bone has been removed, smooth healthy granulations will cover the wound. The continuance of pus from any spot, or the local growth of exuberant granulations, suggest the presence of an infected cell or a fragment of carious bone. Under cocaine anæsthesia, the part should be inspected carefully, and, if necessary, curetted freely. In other cases the local application of chromic or trichloracetic acid is sufficient.

After the second week the wound becomes shallower, actual healing of the wound depending on the size of the cavity.

Unless a very large amount of bone had to be removed, the resulting deformity is not great and usually only consists of slight sinking in of the skin. In some cases the final result is only a fine scar, which can generally be concealed by the hair.

The difficulties and dangers of the operation are considered in the next chapter (see p. 412).

=Results.= 1. If the operation has been successful (and this is usually the case), pyrexia and pain rapidly disappear, the patient experiencing remarkable relief from the head symptoms, so that within twenty-four hours he feels almost well. Healing of the wound is usually complete within six weeks, and before this date the hearing power will probably have been restored to normal.

2. The operation may not have been successful and the following unfavourable symptoms may occur:--

(_a_) The pyrexia may continue irregularly for a few days. If there be no other symptoms, this is probably due to septic absorption from the wound and need not cause very great alarm. If accompanied by pain, it may either mean that all the infected mastoid cells have not been opened, or suggest the onset of osteomyelitis of the temporal bone. If, in addition, such symptoms as rigors, delirium, optic neuritis, headaches, or vomiting occur, they indicate some intracranial complication.

In cases of doubt it is wiser to explore the wound under a general anæsthetic and then to determine what operation will be necessary.

(_b_) The general condition of the patient may be excellent, but otorrhœa or a fistula over the mastoid process may persist. Continuance of otorrhœa, in spite of healing of the wound posteriorly, means that although the disease involving the mastoid process has been eradicated, yet the walls of the tympanic cavity are themselves involved. This will probably necessitate the subsequent performance of the complete mastoid operation.

On the other hand, the suppuration may cease from the middle ear with complete recovery of hearing, and yet a fistula of the mastoid may remain. This means that all the diseased bone has not been removed. This should now be done.

TREATMENT OF SPECIAL CONDITIONS

=In an infant.= In an infant under two years of age the incision should be somewhat higher than usual. In making it, too much pressure should not be used, as the bone is frequently thin at this age, and if carious it may be so soft that the knife may possibly enter the intracranial cavity. In exposing the area of operation, it must be remembered that the posterior root of the zygoma and the antrum lie at a much higher level than in the adult. The opening into the antrum, therefore, is made almost above rather than behind the margin of the auditory canal. In these cases a fistula is usually present, and the bone is so soft that it can generally be removed by means of a sharp spoon or curette. At the same time, however, the aditus should be exposed and the opening made funnel-shaped in order to allow of proper dressing.

=Subperiosteal abscess.= The treatment depends on the extent of the abscess. If it be small, the lining membrane may be dissected away, the wound being afterwards treated in the ordinary manner. If the abscess cavity extends upwards towards the parietal region, or forwards along the temporal fossa, then drainage tubes should be inserted, their ends being brought out into the mastoid wound. It is rarely necessary to make counter-incisions. The completion of the operation is seldom difficult, as the fistula actually leads into the antrum. If the fistula be a large one and the bone is carious a sharp spoon may be used; otherwise a gouge is necessary.

=Bezold’s mastoid abscess.= If the lower portion of the mastoid process be composed of large cells, the abscess within the mastoid may break through the bone at its inner surface in the region of the digastric fossa. In consequence of this the pus may infiltrate the neck tissues beneath the fascia of the sterno-mastoid muscle and form a large abscess recognized clinically as a hard and painful swelling situated below the mastoid process instead of over it. This condition was first described by Bezold.

After exposing the antrum in the ordinary way, the tip of the mastoid process is opened freely. It is usually found to contain large cells filled with pus. Any granulation tissue is curetted away and the cavity dried. The inner surface of the bone is then inspected carefully in order to find the opening, which usually leads into the digastric fossa. The margins of the fistula should be curetted freely and the opening enlarged, if necessary. If the deep-lying cervical abscess be large, the finger may be passed into the abscess cavity behind the mastoid process, between it and the cut fibres of the sterno-mastoid muscle. In this way the limits of the cavity can be made out, and any septa forming pockets within it can be broken down. A counter-incision should be made through the tissues of the neck at the lower limit of the abscess. The opening should be sufficiently large to permit the insertion of a large drainage tube into the cavity. If the abscess be small it may not be necessary to make a counter-opening, but merely to insert a drainage tube into it, passing it from above downwards along the passage made by the finger.

=Necrosis.= In children necrosis of the temporal bone is not uncommon, especially if the middle-ear suppuration occurs in the course of a specific fever or is the result of tuberculous infection.

The part usually affected is the lower margin of the squamous portion of the temporal bone and the tympanic ring. Sometimes, however, the necrosis is very extensive, involving a large area of the petrous bone, including the labyrinth. These cases are always grave, and if a fatal result occurs it is usually in consequence of meningitis.

In adults necrosis is rare excepting as a localized patch usually situated superficially in the cortex of the mastoid process. Partial necrosis of the labyrinth, more especially of the vestibule and the portions of the semicircular canals, is also met with occasionally. When the necrosed area is superficial, such as the squamous portion of the temporal bone or the cortex of the mastoid process, it should be removed. If, however, it be situated more deeply, forcible removal should not be attempted until the sequestrum becomes loose, the wound cavity being meanwhile kept as aseptic as possible.

=Osteomyelitis.= In children, as the result of acute inflammation of the mastoid process, the bone may be found riddled with small points of pus, sometimes termed osteomyelitis. As a result of free opening of the mastoid cavity recovery, as a rule, takes place in the ordinary manner.

Distinct from this is another condition in which thrombosis of the diploic veins occurs. It is, fortunately, a rare complication of mastoid disease. It may occur before operation or be the result of infection of the bone as a result of operation. The infection tends to spread in every direction, more especially upwards along the parietal region and towards the occiput. With this, localized areas of necrosis or abscesses may occur, giving rise to painful swellings on the head, and usually are accompanied by cellulitis of the scalp, pyrexia, and intense headaches.

The only chance of recovery is to expose the affected area freely, and thoroughly remove all the diseased bone. To do this it may be necessary to lay bare the dura mater over a considerable area. If, however, the disease be not quickly eradicated, death will eventually occur as a result of extension of the septic infection to the larger veins, or from some other intracranial complication.