Otogenic cerebellar abscess: an unusual occurrence.

Acquired middle ear cholesteatoma is a well-known sequela of chronic otitis media. Histologically, cholesteatomas are squamous epithelium-lined sacs that contain exfoliated keratin debris. The most common early imaging finding is a small soft-tissue lesion that originates in the pars flaccida and extends into Prussak's space, with or without bony remodeling of the scutum. (1)

As acquired cholesteatomas enlarge, complications can occur, including ossicular erosion, facial nerve canal invasion, tegmen disruption, sinus plate disruption, super-infection, and the development of labyrinthine fistula. (1) Disruption of the tegmen by epidural invasion increases the risk of meningitis, cerebritis, and abscess. (1)

Sennaroglu and Sozeri found that the most common organism detected in otogenic abscesses was Proteus mirabilis. (2) Treatment involves broad-spectrum antibiotics, neurosurgical drainage, and radical mastoidectomy. Mortality rates have improved as a result of early detection with computed tomography (CT), and they now have been reported to range between 10 and 40%. (1-3)

We evaluated a 26-year-old Asian man who had presented to the emergency room with headaches, nausea, vomiting, and a history of chronic purulent drainage from his left ear. His surgical history was significant for a left mastoidectomy that had been performed at another institution 3 years earlier. CT of the left temporal bone detected an aggressive soft-tissue mass with complete erosion of the ossicles, destruction of the mastoid trabeculae, and a labyrinthine fistula (lateral and posterior semicircular canals); CT also detected a hypodense lesion in the cerebellum on the left that was adjacent to a defect in the tegmen (figure 1). Gadolinium-enhanced magnetic resonance imaging (MRI) of the brain demonstrated rim enhancement of the cerebellar lesion and associated central hyperintensity on diffusion-weighted imaging; these findings were consistent with an abscess (figure 2). The CT and MRI findings suggested an aggressive cholesteatoma with superinfection and cerebellar abscess. Postoperative histology confirmed the presence of a cholesteatoma and cerebellar abscess, and cultures grew moderate P mirabilis and heavy alpha-hemolytic streptococci.

[FIGURES 1-2 OMITTED]

References

(1.) Nemzek WR, Swartz JD. Temporal bone: Inflammatory disease. In: Som PM, Curtin HD, eds. Head and Neck Imaging. 4th ed. St. Louis: Mosby; 2003:1173-1229.

(2.) Sennaroglu L, Sozeri B. Otogenic brain abscess: Review of 41 cases. Otolaryngol Head Neck Surg 2000;123:751-5.

(3.) Nalbone VP, Kuruvilla A, Gacek RR. Otogenic brain abscess: The Syracuse experience. Ear Nose Throat J 1992;71:238-42.

Devin K. Tighe, MD; Jessica Borne, MD; David Kirsch, MD; Jose Garayburu, MD

From the Department of Radiology, Louisiana State University Health Science Center, and the Veterans Affairs Medical Center, New Orleans.