High-resolution computed tomographic study of the retrotympanum

Abstract

The aim of this study was to define the imaging of the retrotympanum precisely by means of high-resolution CT. Based on 66 scans of petrous bones performed in 49 patients observed in an otologic department, several retrotympanic structures were studied: the pyramidal eminence, ponticulus, subiculum, chordal ridge, tympanic sinus of Proctor, sinus tympani and recess of the facial n. The variations in morphology and depth were noted as well as the relationship between the pyramid and the facial canal. In a second phase the same anatomic structures were studied in 24 temporal bones removed from embalmed cadavers and investigated with the same radiologic technique. Anatomic correlations were made for six temporal bones to confirm the general applicability of our radiologic hypotheses. In CT the pyramidal eminence was visualised in 100% 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 Proctor 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 tympanic 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 sinuses and their variations will aid the surgeon, particularly in a posterior tympanotomy or a retro-facial approach.

Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study

“…Our study showed that dimensions of the tympanic sinus were highly variable. Both the width and depth of the sinus tympani were measured in numerous studies and in most of them the measurements are consistent with those in our series [ 1 , 3 , 6 , 7 , 9 , 13 , 18 , 20 – 23 , 26 ].…”

“…In the study by Parlier-Cuau et al, the maximal measurement was 9 mm, according to authors ST remained independent of the mastoid cells. The deepened ST may significantly increase the risk of incomplete excision by the classical transmeatal route [ 23 ].…”

“…Basing on the measurements in the current study, the tympanic sinus has a trough-shape; the middle part has the narrowest and deepest dimensions. Wang et al classified ST into three categories: the cup-shaped, the pear-shaped and the boot-shaped, the last one was presented only in patients 2.6 (0.9-6.1) Baklaci et al [3] 2019 HRCT -1.41 ± 0.68 (0.20-3.00) Bekci et al [4] 2020 3D CT --ST volume rise with petrous bone pneumatization Cheita et al [6] 2010 Cadaver 2.00 (1.24-2.76) 2.74 (0.5-6.2) Chen et al [7] 2005 HRCT 1.98 (± 0.71) 2.25 (± 0.91) Donaldson et al [9] 1970 Cadaver -3.75 Kumar et al [13] 2019 Cadaver 1-3 (mean 2.2) 5 (mean 1.72) Mazziotti et al [18] 2006 CT 2.50 (1.5-3.2) 3 (2.3-4.8) Niemczyk et al [20] 2003 Cadaver 2.23 (1.0-3.5) oval Ozturan et al [22] 1996 Cadaver 1.49 (0.49-3.87) 2.06 (± 0.60) Parlier-Cuau et al [23] 1998 HRCT -2.7 (1-9) Saito et al [26] 1971 Cavader 0.96-3.22 (mean 2.14) 2.93 (0.61-5.87) Wang et al [29] 2015 3D HRCT --Cup-shaped, the pear-shaped and the bootshaped with congenital aural atresia [29]. In the literature, the shape of sinus tympani was also described as oval [20] Nitek et al described in most cases the tympanic sinus as elliptical in shape and its long diameter lies in the vertical plane [21].…”

Facial sinus endoscopic evaluation, radiologic assessment, and classification

“…The chordiculus was detected in 52% of the cases, the ST in 95%, and the FS in 80%. When visible in axial sections, the FS appeared pneumatized in 41% of the specimens, and it was reported that its average depth was 2.2 mm …”

A micro-computed tomography study of the sinus tympani variation in humans

“…The sinus tympani (ST) is a depression localized in the retrotympanum (the posterior area of the tympanic cavity) and forms its medial portion. The mean depth of the sinus tympani in adults was estimated to be 2.6 -2.7 mm, but there are also reports stating that it can reach even up to 10 mm [8,16,41]. The sinus tympani lies below and posteriorly to the promontory, posteriorly to the round window, extends medially to the pyramidal eminence, stapedial muscle, and facial canal (its mastoid segment) and laterally to the posterior semicircular canal [19].…”