Hearing Loss

The ear’s primary function is to convert a sound wave into an electric signal transported via the cochlear nerve to the brain, via a process called electromechanical transduction.  The complexity of the ear allows perception of a wide range of tones and loudness levels, distinguish speech from background noise and localise sound.

The ear is divided into the external ear (pinna and ear canal), middle ear (ear drum and ossicles) and inner ear (cochlear and cochlear nerve.) A wide range of pathologic processes can affect each component of the ear mechanism leading to conductive, sensorineural and mixed patterns of hearing loss.

Conductive hearing loss is the result of problems of the external and middle ear. The commonest of these results from wax impaction in the external canal. Other common causes include fluid behind the drum, perforation of the ear drum, ossicular chain problems such as otosclerosis and chronic ear infections with or without cholesteatoma.

Sensorineural hearing loss results from pathology of the inner ear and cochlear nerve. The commonest causes are age related hearing loss and noise induced hearing loss. When there is a difference between the ears a MRI scan is usually required to rule out the presence of more serious pathology such as an acoustic neuroma. There is of course a number of causes that need to be fully assessed and investigated.

Depending on the type and degree of hearing loss, observation, assistive listening devices and hearing aids, surgical reconstruction and cochlear implantation are options available to achieve optimal hearing rehabilitation.

See also St Vincent's Ear, Acoustic Neuroma, and Skullbase Courses for clinicians.