The antrum and mastoid cavity are then thoroughly examined. If a fistula in the bone already communicates with the abscess, pus may be seen to ooze through it. If not, careful search is made for any carious tract of bone, which is now followed up until the dura mater is reached.
After the pus has drained away more bone is removed so as to expose the dura mater fully over the infected area, which is usually vascular or covered with granulations. The latter, however, should be left severely alone. If the abscess be situated in the middle fossa above the tegmen tympani, the bone is best removed by chiselling upwards until the lower margin of the squamous portion of the temporal bone is reached. Then, with a pair of bone forceps, more bone can be punched away quickly until a sufficient opening is obtained ([Fig. 243]).
Exploring with the probe and curetting away of granulations should be avoided as far as possible for fear of injuring the sinus. If its wall be already inflamed, it may be torn through, and the resulting hæmorrhage may render the further steps of the operation a matter of extreme difficulty.
Before completion of the operation, a blunt-pointed seeker should be passed round the edge of the opening in the bone to see that its margin is smooth and even, and all sharp edges of bone bordering on the dura mater should be removed. If this precaution be neglected, a splinter may get pressed inwards and injure the dura mater, and thus set up meningitis.
If possible the bone should be removed until the healthy dura mater is reached. If the extent of the abscess prohibits this, its limits, however, should be ascertained. This can be done by pressing the dura mater inwards with a spatula so as to separate it from the overlying bone.
The final step is to irrigate the cavity with warm boric or saline solution and to insert drains of gauze or of fine india-rubber tubing between the dura mater and bone. The wound cavity is then lightly packed with gauze and a simple dry dressing applied.
After-treatment. Provided there be no other intracranial symptoms, recovery should be as rapid as in the case of simple inflammation of the mastoid process. In the after-dressings, however, special care should be taken not to press in the gauze roughly or tightly against the still inflamed dura mater, in case of injuring its surface and causing further extension of the pyogenic infection to the meninges or lateral sinus. The dressings should be changed daily. It is sufficient to irrigate the wound with some mild aseptic lotion and afterwards to repack it lightly. If Schwartze’s operation has been performed, the after-treatment is similar to that already described (see [p. 387]). In the case of the complete operation, after the purulent discharge has practically ceased and the surface of the wound appears healthy, the packing of the cavity may be carried out through the meatus, instead of through the posterior wound, the latter being then allowed to close.
Intracranial complications. Infection of the lateral sinus is the most frequent complication, but meningitis, ulceration of the surface of the brain, or intracranial abscess may also occur.
One or more of these complications may already exist at the time of operation, but may not be sufficiently marked to warrant further exploration of the intracranial cavity. It is wiser, therefore, to give a guarded prognosis during the first few days after the operation, not only with regard to recovery, but also to the possibility of further operative procedures becoming necessary.