Dimensions and morphology of the sinus tympani: an anatomical study

Abstract

<p class="abstract"><strong>Background:</strong> The sinus tympani is a deep pocket of varying dimensions and shape situated in the retrotympanum. The sinus tympani lies medial to the facial nerve. Hence surgical access is difficult. This area is frequently involved in chronic otitis media attico antral type. Removal of disease from this area is difficult leading to cholesteatoma recidivism. The anatomy has been well described in literature. Its dimensions and morphology has not been described in the Indian population. Knowledge of the endoscopic anatomy of this area will help to eradicate disease leading to better results.</p><p class="abstract"><strong>Methods:</strong> A canal wall down mastoidectomy was performed on twenty wet temporal bones. A zero degree endoscope was introduced into the middle ear to view the sinus tympani. Using a graduated millimetre scale. The dimensions and morphology of the sinus tympani was studied. </p><p class="abstract"><strong>Results:</strong> Twenty wet bones were dissected. The mean height of the sinus tympani was 3.55 mm. The mean width was 2.22 mm and mean depth was 1.72 mm. The morphology was as follows: 13 bones had a type A morphology (classical type), 6 had a type B morphology (confluent), 1 bone had a type D morphology (restricted type). We did not encounter a type C sinus tympani in our study.</p><p class="abstract"><strong>Conclusions:</strong> The morphology and dimensions of the sinus tympani are variable. The otologist must have a complete knowledge of the anatomy of this area to successfully eradicate disease from this area.</p>

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 ].…”

“…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].…”