Malignant Otitis Externa

An Axial CT image of an 82-year-old diabetic man shows marked thickening of the right pinna (arrowhead) and external auditory canal (arrows) without extension to the skull base or evidence of mastoiditis.

Facts: Malignant Otitis Externa

• Severe infection of the external auditory canal (EAC) and skull base
• Elderly diabetics and immunocompromised patients
• Most common organism = P. aeruginosa
• Extension into deep structures or chronic osteomyelitis may occur without signs on local examination
• Potential complications: osteomyelitis of the temporomandibular joint, sigmoid sinus thrombosis, meningitis, optic neuritis
• Biopsy usually required to exclude carcinoma

Staging

1. Stage 1 = confined to EAC and/or facial nerve paralysis
2. Stage 2 = osteitis of the skull base and/or multiple cranial nerve involvement
3. Stage 3 = meninges or brain involvement

Imaging

• CT commonly used to define location, extent of disease.
• MRI may complement CT in cases with cranial nerve, brain involvement
• Imaging monitoring of diseases may be done with bone scan and/or gallium scan

Reference:

Okpala NCE, Siraj QH, Nilssen E, Pringle M. Radiological and radionuclide investigation of malignant otitis externa. J Laryngol Otol 2005;119:71-75.

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