A person suffers from hearing loss if auditory perception is diminished compares to the ability of unaffected individuals. It can be partial or complete, and complete hearing loss is also referred to as deafness. With hearing loss, there may be a loss of perception in the volume or ability to perceive certain frequencies of sounds. Hearing loss is common amongst people older than 65 years.
Sound waves travelling through the ear canal “shake” the ear drum causing the movement of ear bones which in turn, creates waves in the inner ear fluid (air conduction). In bone conduction, vibrations to the skull directly generate these waves. The fluid disturbance bends small hairs (stereocilia) on the cochlea causing stimulation of the auditory nerve which relays the signal to the brain.
Hearing loss may be localized to one ear (unilateral) or affect both ears (bilateral). Acute hearing loss is associated with trauma during accidents or infections while aging and tumors lead to chronic hearing loss.
Additional symptoms of pain and fever are seen during inflammation. Pus secretion and bleeding may happen in cases of severe ear infections. If the auditory nervous system is affected, the patient may present with symptoms such as ringing sensation in the ear (tinnitus) or a spinning sensation (vertigo).
Conductive hearing loss occurs when the transmission of vibration to the hearing apparatus (cochlea) is hampered along the way. This may be due to :
- Ear canal blockage due to accumulated cerumen (earwax), presence of foreign bodies and blood clots.
- Perforations in the tympanic membrane (ear drum) commonly caused by use of cotton swabs to clean ears and microbial infections.
- Dislocated ossicles (ear bones) and skull injuries due to major accidents.
- Otitis externa and otitis media which refers to inflammations in the ear canal and the middle ear, respectively.
If the inner ear or the nerves mediating the generation and transmission of nerve impulse are damaged, the hearing loss is then termed sensorineural hearing loss. This can happen due to :
- Acoustic trauma due to constant exposure to loud noise.
- Inner ear infections.
- Ototoxic drugs (gentamycin, aspirin in high doses, anti-malarial drugs and loop-diuretics).
- Head trauma which damages the auditory nervous system.
- Barotrauma when pressure changes while shifting to high altitudes or under water.
- Acoustic neuroma or tumors of the auditory nervous system.
An audiologist first evaluates the sound perception in each ear by tuning fork and audiometer tests. If symptoms of hearing loss are diagnosed, the ear canal and the ear drum are inspected for visible obstructions, using an otoscope. Blockages in the ear canal are removed by either flushing it with water or suction or by using forceps. Ear wax may be softened with oil drops before the cleaning procedure.
Antibiotics are prescribed to treat microbial infections. Medications that cause hearing loss as a side effect may be discontinued and replaced.
A hearing aid may help by amplifying sounds, in cases of irreversible hearing loss. Permanent cochlear damage can be managed by cochlear implants. In cases of acoustic neuroma, MRI scans will be performed and the case referred to a neurosurgeon. Other treatment measures depend on the underlying cause.