Posterior tympanotomy is a riskier procedure in chronic otitis media than in a normal mastoid: a high-resolution computed tomography study.

Purpose: The aim of our study was to compare the difficulty in performing a posterior tympanotomy in chronic otitis media (COM) versus the same procedure in a normal mastoid.

Materials And Methods: The study included 122 patients who underwent tympanomastoidectomy for unilateral chronic otitis media with contralateral normal mastoid pneumatization. We evaluated the anatomical relationships between the mastoid segment and neighboring structures by analyzing axial temporal bone computed tomography scans. A vertical line (line A) was drawn tangential to the most lateral end of the posterior semicircular canal (point A). Three distances were measured: the distance (D1) between the point A and the most lateral end of the mastoid segment of the facial nerve (point B), the distance (D2) between the line A and the point B, and the distance (D3) between the point B and the posterior end of the bony annulus of the external auditory canal.

Results: The average measurements of D1 and D3 were 3.79 ± 0.55 and 2.63 ± 0.51 mm, respectively, in the normal mastoid ears and 3.47 ± 0.59 and 2.35 ± 0.44 mm, respectively, in the COM ears. The measurements of D1 and D3 were statistically shorter in the COM ears than in the normal ears.

Conclusions: These findings suggest that the facial recess in COM may be narrower than in a normal mastoid and that performing a posterior tympanotomy may be riskier in COM than in a normal mastoid due to the potential for injury to the neighboring structures and the facial nerve.