OPTA 215 ( hearing Loss)
Ear Anatomy and Physiology
Outer ear: Pinna, auditory canal
Middle ear: Tympanic membrane, malleus, incus, stapes, oval and round window,
Inner ear: Semicircular canels, cochlea vesibular nerve, auditory nerve,
Pinna
sound gathering, sound localization
external auditory canal
closed tube, 1 inch length
Transmith sound from outer ear to middle ear
filters low frequency sounds
maximizes the transmission of higher frequency sounds
helps localize sounds
Typanic membrane
-converts acoustic energy of sound pressure wave in mechanicsl vibrations
-composed of 3 layer
-vibrates
Three Ossicles, malleus, incus, and stapes
-moved by vibrations from the typanic membrane
-pressure must be maintained the same between inner and outer ear for the ossicles and typanic to function properly
Eustachian tube
-assist in equalizing air pressure
-run from middle ear to back of throat just above soft palete
Semicircular canels
-balance
-movement
-body position in space
Cochlea
-Bony shell like structure
-Stapes pushes inward on oval window, causes wavelike motion in cochlea
=Inside cochlea is organ of corti (described as the organ of hearing)
Organ of Corti
-Has thousands of hair cells that respond to different frequencies of sound
-When basilar membrane moves, hair cells are bent causing transmission of sound signal to auditory nerve
Auditory nerve
Transmits hearing signals to the brain
Conductive Hearing Loss
Occurs in the outer or middle ear
-Outer or middle ear is unable to conduct sound properly to the inner ear.
-Causes decrease in intensity:Does not distort signal
-A variety of disorders can lead to conductive hearing loss
CHL disorders; Atresia of ear canal
Ear canal fails to develop OR damage occurs:
-Associated with Treacher Collins Syndrome
-Could be a result of trauma like a severe burn
-External otitis (swimmer’s ear)
-Cerumen (earwax) can plug
-Otitis media (inflammation of middle ear)
Note: allergies/sinus infections swell or block the eustachian tube so pressure can’t equalize
CHL Disorders: Ottis media development
Children are more susceptible as e tube is shorter
- eustachian tube blocked
- pressure in middle ear is less than atmosphere pressure
- tympanic membrane reacts
- fluid is drawn from tissue lining in middle ear
- fluid become infected
- infected fluid begin to push against typanic membrane
-fluid pressure builds and causes perforation of the tympanic membrane
Otisis media treatment
Antibiotics (Abx) to kill any bacteria in the existing fluid
-Abx do not promote reabsorption of fluid so children can still be experiencing hearing loss, If child continues to have issues with fluid in middle ear they can have “tubes” inserted surgically that allow for equalization of pressure and reduction of the risk of fluid build up (myringotomy)
Sensorineural Hearing loss
-Occurs when damage to cochlea or any pathways leading to acoustic nerve
-Disrupts volume and distorts signal
-Can be congenital or acquired; More than 50% of congenital hearing loss is related to genetic factors, Are dominant and recessive genes for deafness, Congenital deafness is often associated with other syndromes, ie. Down Syndrome
SHL: aquired
-3rd most common chronic condition in US
-Sensorineural hearing loss associated with aging is called presbycusis:Risk of presbycusis increases as person ages, usually shows around age 60
- Noise is second most common cause: Can get temporary loss from loud noise, if exposure is frequent, can get permanent loss; Common causes?
-Acoustic neuroma: Tumor grows on auditory nerve
-Ototoxicity: Result of medications that can cause hearing loss
-Meniere’s disease: Sudden unilateral loss of hearing
Mixed Hearing Loss
Sensorineural and conductive component
Rehab/ habilitation
- hearing aids
- cochler implants
- Frequency modulated systems and assistive divices
American Sign Language
- signs made by moving hands, facial expressions, and body posture
-primary language for north amercan who are deaf, hard of hearing or mute.
What is the role of the outer ear?
To collect sound