Otology A20


Glue ear & audiogram interpretation

An audiogram plots the softest sound that can be heard across a range of low to high pitch sounds. It graphs frequency (low to high pitch) on the x-axis against hearing threshold (volume of sound heard) on the y-axis. In adults, normal hearing is often 0-25db. Different symbols are used for separating ears and types of conduction. Right (O) and left (X) air conduction plus right ([) and left (]) bone conduction. 

Conductive hearing loss shows a mild loss of air conduction but normal bone conduction. Causes of conductive hearing loss involve pathology in the middle or outer ear and include otitis externa, otitis media, tympanic membrane perforation, and ear wax. 

Sensorineural hearing loss shows a loss of air and bone conduction. Pathology in the inner ear, cochlear and vestibulocochlear nerve cause sensorineural hearing loss. Causes include ototoxicity, presbycusis, Meniere’s disease, infections and genetic defects. 

Mixed hearing loss is a combination of both sensorineural and conductive hearing loss. On an audiogram there will be a gap between air and bone conduction, but both will not be within normal range. A mixture of conductive and sensorineural causes can lead to mixed hearing loss.

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