Figure 3. (a) Laterally there is a very low lying dura (open arrow), which would restrict surgical access to the opaque attic. Erosion of the scutum is again demonstrated. (b) Posteriorly the arch of the lateral semicircular canal is eroded causing an asymptomatic fistula (arrow). (c) Ultimately the cholesteatoma extends into a small, dense, sclerotic mastoid cavity. The canal of the descending portion of the facial nerve is intact (black arrow).