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CT scanning of middle ear cholesteatoma: what does the surgeon want to know?

¹ Department of Otolaryngology, North Riding Infirmary, Newport Road, Middlesbrough TS1 5JE and ² Department of Radiology, South Cleveland Hospital, Middlesbrough, UK

View larger version (171K): [in a new window]   Figure 1. An ideal coronal CT scan with the external and internal auditory canal simultaneously displayed. The scutum is intact (arrow). The stapes suprastructure and incus body (arrowhead) are preserved but the long process of incus has been eroded. The tympanic membrane is retracted onto the stapes head but the middle ear is ventilated.

View larger version (76K): [in a new window]   Figure 2. (a) The scutum is eroded (white arrow) with an attic opacity eroding the malleus head. Medially the cochlea is intact with the labyrinthine and horizontal portions of the facial nerve displayed (black arrow). (b) More posteriorly the middle ear connects with a well preserved, opaque and very extensive cellular mastoid; potentially a huge cavity with a modified radical mastoidectomy.

View larger version (126K): [in a new window]   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).

View larger version (150K): [in a new window]   Figure 4. A woman with history of right total hearing loss after radical mastoidectomy who developed a mild hearing loss in her left, only hearing, ear. She also had a temporary left facial weakness, initially attributed to a Bell's palsy. CT scans confirmed the otoscopically apparent cholesteatoma, with (a) erosion of the scutum and malleus head (arrow). (b) Despite lack of vertigo there is a fistula of the lateral semicircular canal (arrow) and attenuated tegmen. Exposure of the fistula at surgery risked a profound bilateral sensorineural hearing loss in the only functioning ear, so the keratin matrix was preserved. (c) CT of the contralateral ear demonstrates the open mastoid cavity but also the unsuspected fistula of this lateral canal that had resulted in destruction of cochlear function at operation. This defect compares with (d) the intact dome of the semi-circular canal in another, similar, mastoid cavity.

View larger version (171K): [in a new window]   Figure 5. Axial scan through a healthy middle ear cleft and descending facial nerve. The arrow demonstrates the transmastoid, intact canal wall, approach to the facial recess. Medially, the descending facial nerve (arrowhead) is marked by the pyramidal eminence, the origin of the Stapedius tendon. Further medially is a second cleft, the relatively inaccessible sinus tympani.

View larger version (174K): [in a new window]   Figure 6. Coronal scan centred on the stylomastoid foramina (arrows). The patient's healthy ventilated, extensive, cellular, left mastoid system contrasts with the sclerotic bone and the tiny antral cavity, produced by cholesteatoma, on their right.

View larger version (151K): [in a new window]   Figure 7. Extensive cholesteatoma with tegmen erosion and dural exposure. Long neglected erosion into the labyrinth produced a profound sensorineural loss and ultimately, the bony sclerosis obliterating the coil of the cochlea (arrow). Compare with Figures 2a and 4a.