HIGH-RESOLUTION COMPUTED TOMOGRAPHIC STUDY OF THE RETROTYMPANUM - ANATOMIC CORRELATIONS

The aim of this study was to define the imaging of the retrotympanum p recisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, sev eral retrotympanic structures were studied: the pyramidal eminence, po nticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus t ympani and recess of the facial n. The variations in morphology and de pth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were stu died in 24 temporal bones removed from embalmed cadavers and investiga ted with the same radiologic technique. Anatomic correlations were mad e for six temporal bones to confirm the general applicability of our r adiologic hypotheses. In CT the pyramidal eminence was visualised in 1 00% of cases, the chordal ridge in 52%, the ponticulus in 63% and the subiculum in 57%. As regards the different recesses, the sinus tympani was visualised in 95% of cases, the posterior tympanic sinus of Proct or in 38%, the fossula of Grivot in 47% and the facial recess in 80%. The mean depth of the sinus tympani was 2.7 mm and that of the tympani c sinus of Proctor was 1.65 mm; the fossula of Grivot was assessed as 2.1 mm and the facial recess as 2.2 mm. A better knowledge of these si nuses and their variations will aid the surgeon, particularly in a pos terior tympanotomy or a retro-facial approach.