Opening of the deep mastoid cell system andantrotomyAfter having opened Koerner’s septum, the dissection continues by drillingthe anterolateral and superolateral cells, in order to better visualise theantral cavity. Obviously, a smaller-sized burr should be selected (4-5mm or less). Care should be taken, especially in sclerotic bones, not toopen the LSC, the dome of which may be violated by mistake, causingwhat American authors call ‘snake’s eyes’: two small holes on thedome of the LSC (Fig. 18).In order to complete antrotomy, the second landmark to be exposed,after the LSC, is the body with the short process of the incus.It is of the utmost importance to drill the most medial portion of theEAC, between the posterior and superior walls. Stagnation of the irrigationfluid during drilling often causes this structure to be visualised.
(b) – by light refraction – before it is in fact visible in the surgical
cavity (a) (Fig. 19).
This phase, erroneously considered to be the end of hurried dissection sessions, can be considered finished when the following are visible:
• the short process of the incus and fossa incudis, occupied by whitish tissue resembling cholesteatoma or epidermisation (this is the posterior ligament of the incus);
• the dome of the LSC, a compact, mat bone, which is brighter than the surrounding bone;
• the superior aspect (roof) of the antrum, exposing the tegmen antri, which must be at the same level as the tegmen mastoidei, posteriorly and superiorly.
Both superficial and deep cell groups will thus be drilled out
Fig. 20. All the mastoid cells have been exenterated