Computerised tomography: its role in the assessment of ear disease

A retrospective study was undertaken of 205 patients who had been referred for CT scanning of the middle ear and the cerebello-pontine angle. Data from the case notes and radiographs were used to assess the accuracy of high resolution CT in the diagnosis of cholesteatoma and acoustic neuroma, the two diseases which provide the bulk of our work load from the ENT department. The risk factors, including the dose and use of contrast agents, and the cost and time of the examinations has also been considered. An assessment of radiation dose to the eye lens was made for each procedure to indicate the risk to benefit ratio for each radiographic examination. This investigation showed that high resolution CT can accurately diagnose ear disease, while providing an efficient use of resources at low risk to the patient. Positive and negative predictive values of one were obtained for acoustic neuroma; cholesteatomas produced positive and negative predictive values of 0.83 and 0.66 respectively. Plain radiography and polytomography gave information about the bone anatomy of the ear but did not demonstrate the soft tissue component of the disease, so that a negative result from either of these procedures did not exclude a lesion but a positive result was not informative enough to permit surgery.