Hearing loss can be categorized by where or what part of the auditory system is damaged. There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss and mixed hearing loss.
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones, or 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 medically or surgically corrected.
- fluid in the middle ear from colds, allergies (serous otitis media)
- poor eustachian tube function
- ear infection (otitis media)
- perforated eardrum
- Impacted earwax (cerumen)
- Infection in the ear canal (external otitis)
- Presence of a foreign body
- Absence or malformation of the outer ear, ear canal, or middle ear
Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways from the inner ear (retrocochlear) to the brain. Sensorineural hearing loss cannot be medically or surgically corrected. It is a permanent loss.
Sensorineural hearing loss not only involves a reduction in sound level, or ability to hear faint sounds, but also affects speech understanding, or ability to hear clearly.
- birth injury
- drugs that are toxic to the auditory system, and genetic syndromes.
- noise exposure
- head trauma
Definitions of Parts Shown Above
- Helix – The in-curve rim of the external ear
- Antihelix – A landmark of the outer ear
- Lobule – A landmark of the outer ear. The very bottom part of the outer ear
- Crest of Helix – A landmark of the outer ear
- ExternalAuditory Meatus – or External Auditory Canal. The auditory canal is the channel through which the sounds are led from the ear outside to the middle ear.
- Eardrum – (tympanic membrane) A thin layer of skin at the end of the external ear canal
- Auditory Ossicles – The three small bones in the middle ear, know as the hammer (malleus), anvil (incus) and stirrup (stapes) which are connected to one another. Together these ossicles are called the ossicular chain. Their purpose is to lead the sound striking the eardrum further into the inner ear
- Oval Window – An opening in the bone between the air filled middle ear cavity and the fluid filled inner ear, and is covered by a thin membrane
- Cochlea – Part of the inner ear that contains part of the hearing organs.
- Semicircular Canals – Part of the organ of balance that is part of the inner ear
- Eighth Nerve – Nerve that transmits messages from the inner ear to the brain.
- Eustachian Tube – A tube connecting the middle ear cavity and the pharynx (back of the throat). It can be opened by coughing or swallowing, though it is normally closed. The occasional opening of the Eustachian tube is necessary to equalize the are in the middle ear cavity.