Evaluation of Medial Retrotympanum by High-Resolution Computed Tomography and Endoscopy - A Descriptive Study

The aim of this study was to determine and compare the capability of the High-Resolution Computed Tomography (HRCT) and endoscope in detecting hidden areas of medial retrotympanum in cases with chronic otitis media (COM). Per-operative endoscopic evaluation of structures in medial retrotympanum was done in 74 patients suffering from COM and was compared with pre-operative HRCT of the temporal bone in 50 patients. HRCT revealed type-A Sinus Tympani (ST) in 61.2%, type-B in 34.7%, and type-C in 4.1% of the patients; endoscope could reveal type-A in 71.6%, type-B in 25.7% and type-C in 1.4% of the patients. Ponticulus was discovered in 84.1%, subiculum in 100%, finiculus in 97.3% and sinus subtympanicus (SST) in 100% of the cases using endoscope. HRCT could detect ponticulus in 38.6% and subiculum in 4.0% of the cases. HRCT could not very clearly detect finiculus and SST. HRCT could not differentiate the content of the ST as compared with endoscopy. HRCT is a useful diagnostic tool in predicting the presence and type of ST, but its accuracy in detecting SST, finer bony ridges of ponticulus, subiculum, and finiculus and the contents is poorer than endoscope.