As soon as the antrum is reached, pus will be seen to ooze through the opening made, especially if it is under tension. The probe or seeker can now be passed into a cavity of varying size. The antrum is recognized by its smooth surface, which has quite a different appearance to that of the mastoid cells.
(b) If the mastoid be not sclerosed. The pathological condition found on removal of the superficial cortical layer depends on the anatomical structure and on the extent and virulence of the inflammatory process. Only a few cells may be involved, or on the other hand the whole mastoid process, if it be of the pneumatic type, may be converted into a mere shell of bone, forming a large cavity filled with masses of septic granulation tissue, carious bone, and pus. Sometimes, indeed, owing to the tegmen tympani or bony wall of the sigmoid sinus being already destroyed, the dura mater above or the lateral sinus posteriorly may be found already exposed within the cavity. If this is the case the pus may pulsate if present in large quantity. Any patches of soft carious bone or granulation tissue should be removed with the curette.
Fig. 220. Schwartze’s Operation completed. The seeker is being passed through the aditus into the attic. Note the posterior border of the external semicircular canal which forms the inner and lower margin of the aditus.
If the disease be limited to a few superficial mastoid cells, it is sufficient, according to those who do not always explore the antrum, to expose and curette the cavity freely and to do nothing further. This, however, should only be done if the bone surrounding the abscess cavity is hard and apparently normal, and if there is no tract of granulations leading from it in any direction. If an opening be found leading directly into the antrum, it should be enlarged with the curette or gouge. The extent of the antrum is next defined with the seeker, any overlapping ledges of bone being removed by the gouge until the whole of its inner surface is exposed.
The region of the aditus is now inspected under good illumination, using a head-light if necessary. It is recognized as a small opening at the anterior inner part of the antrum, on the floor of which may be seen the posterior border of the external semicircular canal, standing out as a whitish rounded eminence. Bone may be removed from its upper inner margins, but the lower portion should not be interfered with for fear of injuring or displacing the incus. To confirm the opening into the aditus, a blunt-pointed curved probe may be passed for a short distance through the aditus into the attic (Fig. 220).
With the curette all granulations should be removed.
Treatment of the mastoid process. The question now arises as to how much bone to remove. This depends on the condition found; the chief point is to make certain of removing all the infected cells.
In the case of marked sclerosis, the opening need not be large because, if the bone between the cortex and the antrum be solid, it is hardly probable that infection can spread through it to any outlying cells in the tip of the mastoid or elsewhere.
In the diploic and pneumatic varieties, the seeker must be used constantly in order to discover any outlying cells, which are then opened freely. If this be done systematically, infected cells may be found some distance away from the antrum itself, although an area of apparently healthy bone lies between them and the antrum. It must not be forgotten that cells may extend posteriorly as far as the occipital bone, or anteriorly along the zygomatic process, or even into the upper posterior part of the auditory canal itself (see [p. 374]). If such infected cells be not discovered, healing will be prevented.