Hearing loss is a very common medical condition that most people have experienced at least once during their life. There are many causes for hearing loss, some being more severe or permanent than others.
There are two main categories of hearing loss: (1) conductive and (2) sensorineural. To understand the differences, one must first have a basic understanding about the physiology of hearing.
Sound waves move through the outer ear, being directed to the ear drum (tympanic membrane, TM). These sound waves move the TM, which causes 3 small connected bones (ossicles) to vibrate. This vibration causes the intensity of the energy (sound waves) to be increased, or amplified. The vibration is then conducted to the inner ear, where the organ of hearing (cochlea) is located. Within the cochlea there are specialized nerves, known as hair cells, that send the signal to the brain where the sound energy is detected.
Conductive hearing loss is due to an abnormality in transporting, or conducting, the sound energy to the inner ear. Examples would include a wax (cerumen) impaction of the ear canal, perforation of the tympanic membrane, fluid of the middle ear, and disorders of the ossicles.
On the other hand, sensorineural hearing loss is caused by dysfunction of the inner ear or the cochlear (hearing) nerve. The most common causes of this type of hearing loss are secondary to aging (presbycusis) or to excessive noise exposure.
The medical evaluation of hearing loss not only includes a standard examination, but should include a formal assessment of the patient’s hearing status. Historically, physicians used tuning musical forks to determine they type (conductive or sensorineural) and severity of the hearing loss. However, today otolaryngologists and audiologists are able to perform formal hearing tests (audiograms) that are more specific than the tuning fork testing. Based on the formal audiogram, the physician is able to make treatment decisions of the hearing loss.
The treatment for hearing loss depends on the specific cause for it. In general, surgical treatments are used to correct conductive hearing loss, whereas medical devices (such as hearing aids) are used to treat sensorineural hearing loss.
The causes of hearing loss are multiple and varied, as are their specific treatments. If you or a family member are concerned about hearing loss, then an otolaryngology and audiology evaluation may be beneficial.
Robert Wilson, MD.