Shape of the Osseous External Auditory Canal and Its Relationship to Troublesome Cavities.

OBJECTIVES/HYPOTHESIS On the basis of clinical observations, the shape of the osseous external auditory canal (OEAC) has often been seen as an etiological factor in troublesome cavities after modified radical mastoidectomy. STUDY DESIGN Retrospective analysis of CT scans. METHODS To assess the role of the shape of the OEAC in troublesome modified radical cavities using computed tomographic scans of three groups of patients (without pathology and with or without draining cavities), we determined the depth of the pretympanic recess (DPTR) and its anterior curvature (ACPTR). In addition to looking at the shape of the OEAC, we also studied the role of any remaining mastoid air cells in relation to troublesome radical cavities, as well as the consultation frequency. RESULTS The DPTR was significantly deeper in draining cavities than in ears without pathology and dry cavities. No difference in the ACPTR was observed. The presence of remaining mastoid air cells is significantly associated with the presence of a troublesome radical cavity. CONCLUSIONS The shape of the OEAC (i.e., the DPTR) is a contributory factor to the drainage of modified radical cavities. LEVEL OF EVIDENCE 4. Laryngoscope, 126:693-698, 2016.