The value of CT scanning in chronic suppurative otitis media

Abstract

High definition CT has been advocated for the evaluation of chronic suppurative otitis media (CSOM) either generally or in selected cases. It is said to be capable of producing the fine detail needed to detect lateral canal fistulae, exposed dura and facial canal dehiscences, and to demonstrate the ossicular chain. At present there is no agreement on either the indications for CT scanning in CSOM or the most appropriate scanning plane. To determine the value of high definition CT in CSOM and to decide a unit policy for its application, 36 cases of CSOM underwent pre-operative CT scanning and their scans were compared with the operative findings. Our results show CT to be highly sensitive to the presence of soft tissue disease and bone erosion, moderately sensitive to the presence of lateral canal fistulae but less sensitive to the presence of small areas of exposed dura, ossicular continuity and facial canal dehiscence. Axial scans were better able to demonstrate the lateral canal but otherwise coronal scans were superior; ideally patients should be scanned in both planes. The principle value of CT in CSOM is its ability to demonstrate disease which is not clinically apparent.

Computed Tomography in Chronic Suppurative Otitis Media: Value in Surgical Planning

“…In studies on efficiency of HRCT in defining the extent of disease preoperatively, O'Donoghue et al [3] and Mafee et al [4] independently found HRCT to be highly accurate. O'Reilly et al [5] in his study corroborated the above studies with a 100% sensitivity of HRCT in defining the extent of disease. In our study, the sensitivity and PPV were both 96.3% which is in agreement with the aforementioned studies.…”

“…In our study, the sensitivity and PPV were both 54.54%. These non-correlating values can be explained partly by the very small number of patients with tegmen erosion in these studies, and also on the fact stated by O'Reilly et al [5]. He commented that it is not possible to demonstrate reliably a dehiscence in the tegmen on axial scan alone but even using coronal cuts they found that the effect of partial volume averaging with adjacent soft tissues could give a false impression of tegmen erosion.…”

“…O'Reilly et al [5] showed sensitivity of 46% and specificity of 84%. Jackler et al [8] reported a sensitivity of 100% but a PPV of 33.33% in this regard.…”

“…In past studies [3][4][5][6] HRCT was found to be up to 100% sensitive in detecting a soft tissue mass preoperatively. Our data showed a slightly lower sensitivity of 89.65%.…”

“…We therefore must rely on secondary findings to help in differential diagnosis, like ossicular destruction and tendency to gravitate [1]. Thus, after clinical examination, otoscopy and diagnosis of cholesteatoma, HRCT can determine its extent by revealing the combination of a soft tissue mass and bone erosion with 80% specificity [3,5]. Although, cholesteatoma is said to show a lower attenuation than granulation tissue, the difference is subtle and only Magnetic Resonance Imaging can differentiate the two [4].…”