Hearing Loss 

There are two general types of hearing loss: Conductive hearing loss and Sensorineural hearing loss.

Conductive hearing loss is caused by any disruption in the passage of sound from the external ear via the middle ear to the oval window.  Possible causes are impacted waxtympanic membrane perforation, otitis media, middle ear effusion, ossicle problems including otosclerosis. Such hearing losses are often correctable with medical or surgical treatment.

Sensorineural hearing loss results from damage to the delicate hair cells of the cochlea or the nerve fibres of the auditory nervePresbyacusis, or hearing loss related to aging, and noise induced damage are the commonest causes.  This type of hearing loss in one ear may be due to an underlying benign tumour (acoustic neuroma),  Sensorineural hearing loss is generally permanent, though medical treatment of certain conditions can prevent further deterioration.  When the hearing deficit exceeds 30% in both ears a hearing device (aid) is frequently a good solution.  Occasionally a mixed hearing loss, that is part conductive and part sensorineural, may occur.

Diagnostics

Pure tone audiometry, tympanometry and stapedial reflex tests will distinguish beween the different types of hearing loss and provide an indication of the level of disability.  These tests will also enable the response to medical treatment to be measured or deterioration over time to be monitored. Otoacoustic emissions may be measured to screen the cochlea for early signs hair cell damage.  When a patient has a sensorineural hearing loss in one ear, or which is worse in one ear, an MRI scan of the inner ear is essential to rule out a possible underlying acoustic neuroma.