Hearing loss can be categorized by which part of the auditory system is damaged. There are three basic types of hearing loss: conductive, sensorineural, or mixed.
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones (ossicles) of the middle ear. Conductive hearing loss usually involves a reduction in sound level or the ability to hear faint sounds. This type of hearing loss can often be corrected medically or surgically.
Some possible causes of conductive hearing loss:
- Impacted earwax (cerumen)
- Ear infections (otitis media)
- Perforated eardrum
- Benign tumors
- Infection of the ear canal (external otitis)
- Fluid in the middle ear from colds
- Allergies (serous otitis media)
- Poor eustachian tube function
- Presence of a foreign body
Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea), or the nerve pathways from the inner ear to the brain. Most sensorineural hearing loss cannot be surgically corrected or treated medically. Sensorineural hearing loss is permanent hearing loss. Sensorineural hearing loss reduces the ability to hear soft and faint sounds (ie. birds chirping, blinker clicking, consonant sounds of speech). Even when speech is loud enough to hear, it still can sound muffled.
Some possible causes of sensorineural hearing loss:
- Genetics (hearing loss that runs in the family)
- Drugs that may be toxic to the ear
- Exposure to loud noise
- Head trauma
- Birth defects of the inner ear
Mixed hearing loss is a combination of both conductive hearing loss and sensorineural hearing loss.