Background:
Eustachian tube has a major role in ventilation, drainage, and protection of the middle ear. High resolution computed tomography magnifies the role of preoperative imaging for detailed inner and middle ear anatomical information. The aim of this study was to find an applicable way by computed tomography imaging for assessment of Eustachian tube. The goal was to provide improved understanding of the Eustachian tube measurements and the relationship with middle ear in Egyptian population. Computed tomography measurements for Eustachian tube were done including; length of the bony and cartilaginous portions, Total length of Eustachian tube, as well as the width and height of the tympanic orifice of the Eustachian tube. Also, tubotympanic and Reid plane- Eustachian tube angles were measured.

Results:
Within 200 studied ears in 100 subjects, the mean total Eustachian tube length was 40.19 ± 3.05 mm, mean length of the bony Eustachian tube was 11.69 ± 1.8 mm with significant longer Eustachian tube on left side, The mean length of the cartilaginous Eustachian tube was 28.5 ± 2.95 mm with significantly longer cartilaginous and total length in male (P < 0.0001). The mean width and height of the tympanic orifice of the Eustachian tube was 5.4 ± 0.79 and 4.85 ± 0.75 mm, respectively. The mean tubotympanic angle of the Eustachian tube was 148.11 ± 2.82°. The mean Reid plane- Eustachian tube angle was 27.69 ± 2.08° with significantly wider angle in males (P < 0.022).

Conclusion:
The Eustachian tube measurements can easily be obtained on computed tomography images, and are representative for the Eustachian tube anatomy. There is importance of extending computed tomography examinations beyond the middle ear cavity and the mastoids to the Eustachian tube in order to have more data on its condition and relations with different pathological conditions. Computed tomography provides improved understanding of the Eustachian tube measurements and relationship with middle ear structures.