=Difficulties and dangers.= The usual fault is to mistake the congested posterior wall of the external meatus for the membrane.

[Ill.u.s.tration: FIG. 188. TYMPANIC MEMBRANE SHOWING INCISION IN ACUTE SUPPURATION OF THE MIDDLE EAR. Usual line of incision; dotted line shows continuance of incision to make a flap opening for drainage.]

[Ill.u.s.tration: FIG. 189. LINE OF INCISION IN ACUTE SUPPURATION OF THE ATTIC.]

If the patient is not under an anaesthetic, the incision may be made too timidly, the membrane being only scratched. The pain thus inflicted will cause the patient to jerk away the head and probably prevent the membrane from being incised freely. The incision, therefore, must be made in a bold and rapid manner. It is better to make the incision too free than too small.

Care must be taken not to plunge in the knife too deeply for fear of wounding the mucous membrane of the inner wall of the tympanic cavity.

This may result in adhesions between it and the membrane.

Further, cases have been recorded in which a too violent incision has injured or dislodged the ossicles, or in which severe haemorrhage has occurred, presumably from puncturing the bulb of the jugular vein, which was projecting abnormally through the floor of the tympanic cavity.

The two chief causes of failure are insufficient drainage from too small an incision, which may necessitate a further operation, and secondary infection from without.

=Results.= In the majority of cases, provided free drainage is established, the discharge ceases and healing of the membrane takes place from within a day or two to four weeks, depending on the character of the case. If the symptoms continue it may become necessary to perform the mastoid operation (see p. 373).

ARTIFICIAL PERFORATION OF THE TYMPANIC MEMBRANE

The object of the operation is to equalize the pressure within the tympanic cavity and external meatus so as to enable vibrations of sound to be transmitted more readily by the membrane and chain of ossicles to the inner ear.

=Indications.= (i) In the case of an extremely calcified membrane which apparently cannot vibrate.

(ii) To relieve tinnitus or vertigo which appears to be due to an alteration of tension within the tympanic cavity, the result of an impermeable stricture of the Eustachian tube.

(iii) As a means of diagnosis. If the hearing be improved or the subjective symptoms relieved as a result of the artificial opening, then, if the perforation closes (as it probably will do), the surgeon is in a position to suggest some more radical measure, such as ossiculectomy (see p. 351).

=Operation.= Two methods are employed: (i) The knife; (ii) The galvano-cautery. The perforation should be made in the postero-inferior quadrant.

In favour of the galvano-cautery is the fact that the perforation does not tend to close so rapidly. On the other hand, considerable damage may be done unless it is applied with extreme care. For this reason it is wiser to operate under a general anaesthetic, such as gas and oxygen.

If the _paracentesis knife_ be used it is not sufficient to make a simple incision; a small triangular flap must be excised. The operation should be performed under good illumination. The paracentesis knife is inserted boldly through the membrane a little behind and above the umbo.

The membrane is incised in an upward and slightly backward direction towards its margin; then downwards parallel to its posterior border; then horizontally forward, meeting the original point of the incision.

The excised portion of the membrane is removed by seizing it with a fine pair of crocodile forceps, or by means of a fine snare, if it has not been completely detached.

The _galvano-cautery_ is applied cold; when it is in contact with the drum, the circuit is closed so that the point of the cautery becomes red-hot. After the membrane has been burnt through it is withdrawn rapidly so as not to scorch the surrounding tissues. In using the cautery care must be taken to push it only just through the membrane for fear of injuring the inner wall of the tympanic cavity.

=After-treatment.= The after-treatment consists in protecting the ear by a strip of gauze, which is changed as often as may be necessary.

DIVISION OF THE ANTERIOR LIGAMENT

=Indication.= It is advised by Politzer in those cases of marked retraction of the drum in which inflation causes an immediate improvement in hearing, which, however, only lasts a short time. In several cases Politzer found the cause of this to be due to tension of the anterior ligament causing retraction of the malleus.

[Ill.u.s.tration: FIG. 190. LINES OF INCISIONS IN INTRATYMPANIC OPERATIONS.

A, Removal of membrane in ossiculectomy; B, Division of posterior fold; C, Division of anterior ligament.]

=Operation.= The anterior fold is divided with the paracentesis knife just in front of the processus brevis of the malleus. The knife is then introduced 2 millimetres inwards through the incision and made to cut in an upward direction as far as Shrapnell's membrane (Fig. 190, C). This should divide the ligament.

If the operation be successful, improvement in hearing and also diminution of the subjective noises should take place.

DIVISION OF THE POSTERIOR FOLD

=Indication.= The same as for the anterior ligament. Owing to the increased tension of the upper posterior quadrant of the tympanic membrane, it is a.s.sumed that the movements of the malleus are diminished, and with this the hearing power. Seeing, however, that the prominence of the posterior fold is due to the projection outwards of the processus brevis as a result of the handle of the malleus having become indrawn with the membrane, it is difficult to understand how its division can possibly be a means of restoring the retracted membrane to its normal condition.

On the few occasions on which I have performed this operation, no improvement has followed. Others, however, maintain that it may do good in certain cases. This, perhaps, may be possible if it is combined with other intratympanic operations, such as division of the anterior ligament or of the tensor tympani muscle.

=Operation.= The paracentesis knife is inserted through the most prominent part of the fold and is made to cut through it from above downwards (Fig. 190, B). If this is successful, gaping of the cut edges takes place and the membrane a.s.sumes a less retracted position, and increased hearing and diminution of the subjective symptoms should occur on inflation and rarefying of air within the external ear.

INTRATYMPANIC OPERATIONS

=General considerations with regard to intratympanic operations and their results.= The chief difficulty, from a clinical point of view, is to determine beforehand the exact pathological changes which already exist within the tympanic cavity. For this reason the indications given with regard to operation are of necessity somewhat empirical. For example, retraction of the tympanic membrane may be due to closure of the Eustachian tube; to adhesions between it and the promontory; to contraction of the tensor tympani, of the anterior ligament, or of the posterior fold. An operation to remove only _one_ of these causes may, therefore, be insufficient; the difficulty is to know what to do. Even if further operations are performed, the result may be negative owing to adhesions having taken place already between the ossicles themselves, or from binding down of the incudo-stapedial joint or of the stapes to the inner wall of the tympanic cavity. And apart from this, even if temporary benefit is obtained, the final result may be worse than that which existed before operation owing to the natural tendency for adhesions to re-form.

The prognosis is better in the case of post-suppurative conditions than in the non-suppurative ones.

Improvement by operation may be hoped for if a temporary increase in the hearing power, with diminution of the subjective symptoms, is obtained as a result of inflation; especially in those cases in which the malleus is only locally adherent to the promontory.

Generally speaking, however, these operations are not recommended, owing to the impossibility of being able to give a good prognosis, and therefore they can only be considered as experimental.

_These operations are contra-indicated_--(1) If there be internal-ear deafness.

(2) If the stapes (as shown by tuning-fork tests and Gelle's test) be ankylosed within the fenestra ovalis, especially in the case of otosclerosis.

(3) If the membrane be completely adherent to the inner wall at its upper posterior quadrant, especially if this is of long standing, as the stapes will almost certainly also be fixed by adhesions.

DIVISION OF INTRATYMPANIC ADHESIONS

The position and extent of the intratympanic adhesions vary exceedingly, and may be the result either of middle-ear catarrh or suppuration. The following conditions may be found:--

(i) Adhesion of the handle of the malleus to the promontory, the rest of the tympanic membrane being movable.

(ii) Adhesions between other parts of the tympanic membrane and the inner wall of the tympanic cavity, either by bridles or bands of fibrous tissue, or by the membrane itself being adherent over a large area.

(iii) Adhesion of the edge of a perforation to the inner wall.

(iv) Adhesions surrounding the articulation between the incus and stapes, and the stapes itself.

[Ill.u.s.tration: FIG. 191. CUTTING THROUGH INTRATYMPANIC ADHESIONS. The malleus is adherent to the promontory. A, Surface view; B, Vertical section. _a_, Handle of the malleus; _b_, Membrane adherent to the promontory; _c_, Line of incision to cut through the membrane.]

=Indications.= Operation is justifiable in the case of adhesion of the malleus to the promontory if the rest of the membrane is freely movable; if the membrane bulges outwards and there is temporary improvement in hearing on inflation; and if examination shows that the labyrinth is intact. This operation is all the more indicated if there is marked deafness on both sides: it should then be attempted on the worse side.

If, however, the intratympanic adhesions are extensive, it is very doubtful whether an attempt to separate the free part of the membrane from the part adherent to the inner wall is worthy of consideration.

It must also be remembered that adhesions in the region of the stapes cannot be seen, unless a large perforation of the membrane already exists. Operation is then only justifiable as a last resource if there is extreme deafness accompanied by distressing subjective symptoms.

=Operation.= Unless the patient is very sensitive or nervous, local anaesthesia is sufficient. It is more convenient for the patient to be sitting up in a chair than to be in the rec.u.mbent position. The surgeon works by reflected light. Before the operation is begun, the ear must be surgically cleansed and carefully dried.