Application of Otoform to Study Variations of Sinus Tympani: A Novel Technique

The sinus tympani is a deep pocket of varying dimensions situated in the retrotympanum. It lies medial to the facial nerve thereby making surgical access difficult. It is this area which is frequently involved in chronic otitis media attico-antral type. Removal of disease from sinus tympani is cumbersome and expedites Cholesteatoma Recidivism. In India, very limited studies have been conducted describing the variations of Sinus tympani. Hence, this study is dedicated to estimating it's variations in volume. This is a one-year Observational Cross-sectional study conducted between January 2020 to December 2020 in Temporal Bone Dissection Lab of Department of Otorhinolaryngology and Head and Neck Surgery, J. N. Medical College, KAHER, Belgaum. 40 Human temporal bone (both left and right) have been dissected. The middle ear cavity was filled carefully with a moulding material i.e. Otoform. Once set, a 3-dimensional model of the middle ear cavity was made, which was removed carefully without causing any damage. The volume of the middle ear cavity was calculated. The other contents and parameters were measured using a measuring probe. Forty bones were dissected. The volume of the sinus tympani was measured to be 8.77 cubic mm with a range of 6.5 cubic mm to. 10.9 cubic mm hence showing that sinus tympani show a larger variability in terms of size, shape and volume. The ponticulus was Complete in 65% of the cases (26 bones) and incomplete in 35% of the cases (14 bones). The ponticulus and subiculum were found to be complete in a well pneumatized mastoid bone. The volume of the middle ear cavity was measured to be 1.17 cubic cm. The sinus tympani volume was calculated in this study employing a novel technique called the Otoform mould in cadaveric temporal bones, enabling for accurate measurement. The study concluded that sinus tympani showed a wide range in volume thus owing that it is the structure which has highest variability in terms of size and shape in the middle ear.