Comparison of Depth of Mastoid Antrum on High Resolution Computed Tomography and Per Operatively in Cases Undergoing Mastoidectomy.

To compare the depth of mastoid antrum on High Resolution Computed Tomography and per operatively in cases undergoing mastoidectomy. This prospective observational study was done in a tertiary care Army Hospital with 35 patients meriting cortical mastoidectomy surgery. The patients underwent HRCT of temporal bone as a routine pre-operative work up, where depth of mastoid antrum was measured from dome of lateral semicircular canal to outer cortex of temporal bone. Depth was also recorded per-operatively with the help of measuring scale. Measurements were correlated and data was analysed statistically. There were 12 male patients and 23 females. 6 patients were < 3 years of age and 29 above. Study included 29 cases of Chronic Otitis Media and 6 of Bilateral Congenital Sensorineural Hearing Loss. Mean depth of mastoid antrum was 1.625 cm ± 0.228 on HRCT, and 1.651 cm ± 0.245 per-operatively. Depths of mastoid antrum on HRCT and per operatively amongst paediatrics as well as adult cases were comparable, but were more than the standard depth of 1 cm in 5 (82.3%) paediatrics cases and ˃1.5 cm in 24 (82.9%) adult patients. In absence of Koerner's Septum, mean HRCT depth was 1.60 cm ± SD 0.23 and per operatively was 1.63 cm ± SD 0.21; whereas in its presence mean HRCT depth was 1.84 cm ± SD 0.069 and per-operatively was 1.85 cm ± SD 0.42. Significant difference in depth was noted between adults and children, and between the cases with or without Koerner's Septum. However, difference in depth was not significant when compared between different genders, laterality of disease or disease pathology.