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 ca.n.a.l, 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 periost.i.tis 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 periost.i.tis 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, fistulae or other evidences of mastoid disease almost invariably occur afterwards.

=Operation.= In an infant a general anaesthetic is not necessary, but in an adult gas anaesthesia 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 haemorrhage 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 otorrha 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 otorrha 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 otorrha is presumably due to acc.u.mulation 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 s.p.a.ce 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 anaesthetized, the cleansing process should be repeated, and the auditory ca.n.a.l 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 rec.u.mbent 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.

[Ill.u.s.tration: FIG. 216. DIAGRAM SHOWING POSITION OF SKIN INCISIONS IN POST-AURAL OPERATIONS. 1, For removal of foreign bodies or exostoses, or for excision of a stricture within auditory ca.n.a.l; 2, Usual incision for the mastoid operation; 3, Prolongation of incision upwards for exposure of temporo-sphenoidal lobe; 4, Extension of incision backwards, for exposure of lateral sinus or cerebellum.]

_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).

[Ill.u.s.tration: FIG. 217. SCHWARTZE'S OPERATION. Showing field of operation with anatomical landmarks and gouge in position for opening of antrum.

A, Zygomatic ridge; B, Spine of Henle: behind and above it is the suprameatal triangle; C, Fibrous portion of cartilaginous meatus, not separated from bony. (In this and the following diagrams the gouge or chisel is drawn small. In actual practice they may be much larger.) ]

_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 a.s.sistants, 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 a.s.sistant, 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 a.s.sume 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 ca.n.a.l 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.