NWC Chee, TY Tan
Correspondence: Dr Nelson Chee, nelson_chee@notes.ttsh.gov.sg
ABSTRACT
Introduction Cholesteatoma is traditionally diagnosed by otoscopic examination and treated by explorative surgery. The need for imaging in an uncomplicated case is contentious. This study assesses the usefulness of a pre-operative high-resolution CT scan in depicting the status of the middle ear structures in the presence of cholesteatoma.
Materials and Methods The surgical findings of 36 ears with cholesteatoma operated on by the first author were retrospectively compared with the CT findings reported on by the second author. The following were analysed: diagnostic features of cholesteatoma on CT, status of the middle ear structures (ossicles, facial nerve canal, semicircular canals and tegmen tympani), and presence of any anatomical variations and disease complications.
Results All cases had at least 1, and 30 cases (83.3%) had all, of the following radiological features: (a) a non-dependent tissue mass, (b) a location typical for cholesteatoma and (c) bony erosion. The radiosurgical agreement was excellent for the malleus (kappa statistics, k=0.83), stapes (0.94) and semicircular canals (0.8), good for the incus (0.62) and tegmen (0.65), but poor for the facial nerve canal (0.3). Potential surgical hazards detected by the scans included: low lying dura, high jugular bulb, anterior lying sigmoid sinus, facial nerve dehiscence and other situations brought about by the destructive nature of the lesion.
Conclusion There is good to excellent radiosurgical correlation in cholesteatoma for most middle ear structures except for the integrity of the facial canal. The scan alerts the surgeon to potential surgical dangers and complications of disease. High-resolution CT scan is an important investigative tool prior to cholesteatoma surgery.
Keywords: mastoidectomy, ossicles, facial canal, labyrinthine fistula
Singapore Med J 2001; 42(4): 155-159
