Otoscopy :: THE EXTERNAL CANAL :: Fig7_34
 THE EXTERNAL CANAL  
Necrotizing Otitis Externa
(Previously Known as "Malignant Otitis Externa")

Necrotizing Otitis Externa
(Previously Known as "Malignant Otitis Externa")

Description : Definition
A severe and aggressive erosive form of otitis externa which occurs in elderly
diabetics and otherwise immunocompromised patients.

This condition is frequently fatal unless recognized and energetically treated at an early stage.

Malignant otitis externa is not malignant in the sense of neoplasia, but is potentially lethal due to the fulminating spread of infection which may involve bone, cranial nerves and the cranial contents.

A better descriptive title for this condition would be "Invasive otitis externa"!

Etiology
The causative organism is Pseudomonas aeruginosa, which is invariably found; the patient is almost always either diabetic or a severely immunocompromised individual. I

n these patients there appears to be a defect in the immune defence system which would normally limit the invasive capability of this bacterium.

Symptoms
The initial symptoms are those of an acute otitis externa, with local pain and discharge from the ear canal. As the infection progresses, the pain becomes quite severe and unremitting, and cranial nerve palsy may appear.

Malignant otitis externa is characterized by the progressive spread of infection from the ear canal into the adjacent structures. Frequently, the infection will spread into the temporal bone, causing osteomyelitis which may extend to the base of the skull, resulting in multiple cranial nerve palsies, meningitis, brain abscess or death.

Otoscopic appearances
The meatus is filled with a purulent discharge. The hallmark of malignant otitis externa is an area of infected granulation tissue on the floor of the cartilaginous ear canal near the junction between the cartilaginous and bony portions of the canal as seen here.
If the granulation tissue is removed, a defect may be found tracking under the bony external canal. The overlying skin is swollen and granulation tissue is often present within the external canal, arising from the junction of the bony and cartilaginous portions.

Granulation tissue with a mucoid exudate is seen arising from the junction between the bony and cartilaginous portions of the canal.

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