High Resolution Computed Tomography Study of the Length, Width & Angle of Eustachian Tube in Normal Ear and in Chronic Otitis Media.

Abstract

Eustachian tube is complex and inaccessible structure. It connects nasopharynx to middle ear. It is composed of cartilaginous and bony segments. Eustachian tube helps in pressure regulation, protection and clearance of the middle ear. Dysfunctions of Eustachian tube are either due to anatomical obstruction or functional failure. Whether variation of length, width of bony canal, isthmus, length of the cartilaginous canal and angulation of the Eustachian tube to horizontal plane affects overall pressure regulation, protection and mucociliary clearance leads to the spread of the infection to the middle ear are highlighted. A comparative prospective study design of 20 adults of both gender of normal ear computerized tomography done for some other cause and 20 adults of both gender with chronic otitis media (tubo-tympanic pathology). After obtaining consent, clinical examination, all patients had got computerized tomography study of the temporal bone and were evaluated to study the variation of length, width of bony canal, isthmus, length of the cartilaginous canal and angulation of the Eustachian tube to horizontal plane. In our series cartilaginous Eustachian tube length is 26.72 mm in normal ear and 26.17 mm in diseased ear. Long and reduced diameter of bony segment is the anatomical cause in the tubotympanic pathology along with inflammation and loss of ciliary moment. Normal ear bony width is 2.36 mm; isthmus 1.18 mm are comparatively more than diseased ear (bony width 2.13 & isthumus1.04). Whereas bony length of normal ear is 11.21 mm and diseased ear is 11.62 mm. Decreased Eustachian tube pretympanic diameter and Reid -plane ET angle can be used to predict Eustachian tube dysfunction. Angle to horizontal plane in our series in normal ear 44.670 whereas in diseased ear 45.10. The Eustachian tube plays an important role in the development of the tubotympanic pathology of the ear. Pre-existing Eustachian tube anatomical variation appears to be risk factor in developing tubotympanic pathology.