The sinus tympani lies medial to the pyramid, stapedius muscle and vertical part of facial nerve.
Baki et al studied the endoscopic anatomy of the sinus tympani and found that the sinus tympani is bounded laterally by a constant ledge of bone anterior to the facial nerve.
For instance, the facial canal, which lies in the lateral wall of the sinus tympani, may protrude into the sinus to form a recess under the nerve.
Sinus tympani: Anatomic considerations, computed toarography, and a discussion of the retrofacial approach for removal of disease.
Indications for a second-look procedure include (1) excessive bleeding or inflammation that prevents full visualization of cholesteatoma, (2) a suspicion that cholesteatoma has been only incompletely excised, especially in the sinus tympani, on the facial nerve, or on the ossicular chain, and (3) reconstruction of the ossicular chain in a less-inflamed environment.
Endoscopes can be used for both primary and second-look procedures to facilitate visibility into the sinus tympani and attic.
This exposure were also enough for C1a (Lateral epitympanum and Prussak's space lesions), C2b (Mesotympanum, Protympanum, sinus tympani
and Hypotympanum cholesteatomas), C2c (Posterior and inferior extensions) lesions and C3 cholesteatoma involving retrotympanic space (Sinus tympani/subtympanic sinus; subpyramidal space) and or with facial nerve involvement.
According to this study, cholesteatoma had extension beyond the aditus and antrum, 61% of attic, 37% of sinus tympani
, and 16% of tensa.7 In tympanic cavity, oval window and sinus tympani
were the most commonly involved parts (46.7% and 40.7%).
Pars flaccida Pars tensa Posterior wall remodeling 61% 83% Opening of eustachian tube 83% 95% Ossicular erosion 77% 83% Scutum erosion 61% 58% Tegmen tympani defect 2% 0% Round air-filled defect 20% 87% Opening of sinus tympani
61% 45% Labyrinthine fitsula 0% 0% Tympanic membrane retraction 75% 75% Autoatticotomy/mural cholestoma Posterior wall remodeling 80% Opening of eustachian tube 86% Ossicular erosion 100% Scutum erosion 100% Tegmen tympani defect 20% Round air-filled defect 73% Opening of sinus tympani
33% Labyrinthine fitsula 13% Tympanic membrane retraction 86% Note: Table made from bar graph.
Most of these techniques were designed to provide a better view of the posterior tympanic cavity--specifically, the sinus tympani
. They include reversing the surgeon's orientation, using mirrors to see around bony ridges, and temporarily removing the posterior canal wall.
The PTA and mean ABG in patients with cholesteatoma involving the epitympanum, facial recess and sinus tympani
was 53.30 dB and 36.60 dB respectively.
Advocates of complete CWDM justify its use as it provides a good view of the mesotympanum and sinus tympani
to ensure complete expiration of the cholesteatoma and to avoid recurrence.