Clinical features of CSOM with a central perforation
THE CONTEXT
The described clinical pattern includes nonoffensive discharge, predominantly conductive hearing loss, a central perforation and changes in visible middle ear mucosa.
Ear discharge
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Discharge is nonoffensive and mucoid or mucopurulent. It may be constant or intermittent.
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It appears mostly during upper respiratory tract infections or after accidental entry of water into the ear.
Hearing loss and its mechanisms
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Hearing loss is conductive, varies in severity and rarely exceeds 50 dB.
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Some patients hear better with discharge than with a dry ear because discharge shields the round window and helps maintain a phase differential.
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In a dry ear with a perforation, sound strikes the oval and round windows simultaneously, cancelling their effects.
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In long-standing cases, toxins absorbed through the oval and round windows may damage the cochlea, causing mixed hearing loss.
Perforation and middle ear mucosa
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The perforation is always central and may lie anterior, posterior or inferior to the handle of the malleus.
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It may be small, medium or large; extension up to the annulus is termed subtotal.
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Middle ear mucosa is visible through a large perforation. It is normally pale pink and moist but becomes red, oedematous and swollen when inflamed.