Fig. 190. Lines of Incisions in Intratympanic Operations. A, Removal of membrane in ossiculectomy; B, Division of posterior fold; C, Division of anterior ligament.
Indication. The same as for the anterior ligament. Owing to the increased tension of the upper posterior quadrant of the tympanic membrane, it is assumed 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 assumes 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.