Preliminary exploration of the mastoid operation, followed by an investigation of the middle and posterior fossæ of the skull. To expose the mastoid antrum, the incision commences immediately above and behind the ear, and, carried down to the bone throughout, terminates near the tip of the mastoid process. The soft tissues are peeled away in the forward direction and the cartilaginous ear detached from the posterior and upper boundaries of the bony auditory meatus.
Macewen’s suprameatal triangle and the supramastoid crest are identified, the former landmark being taken as a guide to the communication between the mastoid antrum and the middle ear, the latter representing the uppermost limit of the field of operation.
Fig. 80. The ‘Radical’ Mastoid Operation. To show removal of the ‘bridge’ from above. The seeker, inserted into the aditus, acts as a protector to the underlying external semicircular canal and facial nerve. (After Hunter Tod.)
With the aid of the hammer and chisel the bone is chipped away till the antrum is exposed—on an average this will be situated about three-fifths of an inch deep from the surface. The opening necessarily becomes funnel-shaped, but it should be made as complete as circumstances permit.
As soon as the antrum is exposed, the seeker or nerve-protector should be introduced into the aditus, acting as a protector to the underlying external semicircular canal and facial nerve, and the ‘bridge’ of bone, which now intervenes between the antrum and the middle ear, chiselled away, in the manner indicated in [Fig. 80].
The field of operation is now carefully cleansed, cholesteatomata, bone-debris, and ossicles being gently removed, and—with the aid of a head-lamp—a careful search instituted for fistulous tracts, carious bone, &c. This search must be carried out with the greatest gentleness for fear of inducing further complications.
Subsequent procedures vary according to the nature of the conditions found. Thus:—
1. When the diagnosis is uncertain and when the boundaries of the cavity appear fairly healthy, the operation may terminate at this point, a post-meatal flap being formed and the cavity lightly plugged with gauze. The proximal end of the gauze plug is brought out through the enlarged auditory meatus and the ear-flap sewn back with a few salmon-gut sutures.
