Recognizing tympanostomy tubes on temporal bone CT: typical and atypical appearances

Department of Radiology, Wayne State University/Detroit Medical Center, Canfield, MI 48201.

Myringotomy with placement of a tympanostomy tube is a common surgical procedure. Although CT is not performed to evaluate these tubes, recognizing and accurately reporting their presence are important for a number of reasons. These include misidentification of the tube as a foreign body or a dislocated ossicle, misidentification of debris or normal ossicles as a tympanostomy tube, confirmation of the presence of a tube not seen on otoscopic evaluation, stimulation of careful search for cholesteatoma, and documentation of intervention. The purpose of this study is to show the CT appearance of tympanostomy tubes and to determine factors that make their identification on CT difficult. We reviewed all CT studies of the temporal bone performed over a 1-year period to determine the presence and appearance of tympanostomy tubes. Of the 118 CT scans evaluated, 19 patients (16%) had 34 tympanostomy tubes; of these 34 tubes, 13 (38%) had CT features that hindered identification of the tubes. Factors that resulted in obscured tubes, in order of frequency, included surrounding fluid, technical problems such as motion and artifacts, and atypical location. By knowing the appropriate location and CT appearance of tympanostomy tubes, misidentification of the tubes can be avoided.
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