Hearing loss is classified either as congenital (if it occurs before birth) or acquired (if it occurs after birth).
Congenital hearing loss may be caused by hereditary factors as well as by disease or medical conditions suffered by a fetus. Genetic factors are thought to cause more than 50% of all incidents of congenital hearing loss in children. Genetic hearing loss may be autosomal dominant, autosomal recessive, or X-linked (related to the sex chromosome).
Hearing loss in adults, also known as acquired hearing loss can result from any of a variety of causes, including:
- Natural ageing process - is the most common cause of hearing loss
- Exposure to loud or constant noise - Prolonged exposure to noise and even brief exposure to loud noise can cause
permanent hearing loss.
- Disease - Diseases, such as Meningitis, Meniere's disease, and benign growths and tumours on the hearing nerve, can cause hearing loss.
- Toxic medication - Some medications including antibiotics can damage hair cells in the inner ear and auditory nerve. Among them are quinine, aminoglycosides, diuretics, large doses of aspirin, and some chemotherapy agents.
- Ear infections - Otitis media, characterized by accumulation of fluid in the middle ear, can lead to hearing loss, allergies, common colds, sore throats, inflamed tonsils and adenoids, blocked eustachian tubes. Viruses can also cause Otitis media.
- Injury - Perforation of the eardrum can be caused by rapid changes in air pressure (like
those which occur when flying or scuba diving), foreign objects (such as cotton
swabs that are used to clean the ears), or pressure caused by a middle-ear infection.
- Earwax - A build-up of wax (cerumen) in the ear canal can prevent sound from passing through the ear.
Types of Deafness
There are basically two types of deafness. One is caused by problems with the sound reaching the inner ear. Since the sound travels there via conduction, this is called conductive hearing loss. It's the far less common mechanism of hearing loss.
Much more common is sensorineural hearing loss. This is often called nerve deafness, even though the auditory nerve is almost never the cause. The problem is usually in the hair cells of the cochlea.
