What are forms of hearing loss?
Hearing loss, or deafness, can be present at birth (congenital), or become evident later in life (acquired). The distinction between acquired and congenital deafness specifies only the time that the deafness appears. It does not specify whether the cause of the deafness is genetic (inherited).
Acquired deafness may or may not be genetic. For example, it may be a manifestation of a delayed-onset form of genetic deafness. Alternatively, acquired deafness may be due to damage to the ear due to noise or from other conditions.
Congenital deafness similarly may or may not be genetic. For example, it may be associated with a white forelock, and be caused by a genetic disease called Waardenburg syndrome. In fact, more than half of congenital hearing loss is inherited. Alternatively, congenital deafness may be due to a condition or infection to which the mother was exposed during pregnancy, such as the rubella virus.
What are the types of hearing loss?
Hearing loss can also be classified based on which portions of the hearing system (auditory system) are affected. When the nervous system is affected, it is referred to as sensorineural hearing loss. When the portions of the ear that are responsible for transmitting the sound to the nerves are affected, it is referred to as conductive hearing loss.
Conditions affecting the cochlea, eighth cranial nerve, spinal cord, or brain cause sensorineural hearing loss. Examples include:
- Meniere's disease,
- noise-induced hearing loss (such as prolonged or excessive exposure to loud music or machinery),
- hearing loss of aging (presbycusis),
- nerve injury from syphilis,
- hearing loss of unknown cause (idiopathic hearing loss),
- nerve tumors and;
- drug toxicity (such as aspirin and aminoglycosides).
Conditions that affect the ear canal, eardrum (tympanic membrane), and middle ear lead to conductive hearing loss. Examples of conductive hearing loss include:
- ear wax blocking the ear canal,
- otitis media and;