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Neuroradiology Case of the Week

Case 136

Osbert N Adjei, MD, Jeevak Almast, MD,
and PL Westesson MD, DDS, PhD

Clinical Presentation: Patient is a 46-year-old male with right-side hearing loss.

Radiological Findings: CT of the right temporal bone showed a middle ear soft tissue mass. There is erosion of the scutum and ossicles. There is thinning of the tegmentum tympani. The mastoid air cells are opacified.

Discussion: Cholesteatoma is a destructive lesion of the skull base that can erode into and destroy important temporal bone structures. Middle ear cholesteatoma can be congenital or may result from direct trauma. It may also be secondary to ear infections usually due to poor eustachian tube function. Dead cells accumulating from the infection produce enzymes that cause adjacent bone destruction. Bone erosion also results from direct pressure effect from the expanding cholesteatoma. The affected bones include the ossicles and labyrinth, and other adjacent bony structures. The net results of the above include conduction and sensorineural hearing loss, dizziness and facial nerve paralysis. Other sequelae of middle ear cholesteatoma include meningitis, brain abscess and hydrocephalus.
     The initial symptoms of cholesteatoma are painless otorrhoea and hearing loss. Less typical initial presentations (seen more commonly in children) include neck abscess, sigmoid sinus thrombosis, epidural abscess and meningitis.
      CT scan is the imaging modality of choice for cholesteatoma. This is due to its higher sensitivity for subtle bony defects, including scutal erosions, labyrinthine fistulas, tegmental defects, and details of ossicular involvement, erosion or discontinuity, and anomalies of the fallopian canal.  However, CT cannot distinguish between cholesteatoma and granulation tissue in certain clinical situations. This limits accurate determination of the full extent of disease to facilitate optimal surgical planning in such patients.
      MRI is limited to specific clinical situations. These include evaluation of suspected dural involvement, subdural or epidural abscess, sigmoid sinus thrombosis and inflammation of the facial nerve and membranous labyrinth.

References:

1. Watts S, Flood LM, Clifford K. A systematic approach to interpretation of computed tomography scans prior to surgery of middle ear cholesteatoma. J Laryngol Otol. 2000 Apr;114(4):248-53. [Medline]
2. Maroldi R, Farina D, Palvarini L, Marconi A, Gadola E, Menni K, Battaglia G. Computed tomography and magnetic resonance imaging of pathologic conditions of the middle ear. Eur J Radiol. 2001 Nov;40(2):78-93. [Medline]
3. Minor LB. Labyrinthine fistulae. Labyrinthine fistulae: pathobiology and management. Curr Opin Otolaryngol Head Neck Surg. 2003 Oct;11(5):340-6. [Medline]