Ear Disorders Flashcards
anatomy review
Eustachian tube
links the cavity of the middle ear to the nasal cavity and provides a route to equalize air pressure between the middle ear and the atmosphere
outer ear includes
pinna, auditory canal, ends at TM
middle ear includes
TM, malleus, incus, stapes,
inner ear includes
cochlea, semicircular canals, eustacian tube
ear
each labrinth has two parts
The cochlea is the auditory part of the labyrinth. Afferent neurons exiting the cochlea form the auditory (cochlea) nerve, which is part of the vestibulocochlear nerve (CN VIII).
The otolith organs and the semicircular canals form the vestibular part of the labyrinth. Afferent neurons from these organs form the vestibular nerve, which joins with the auditory nerve to form CN VIII.
Audiometry
normal range for human hearing
The normal range of human hearing is about 20 to 20,000 Hz. Some animals can hear up to 50,000 Hz. Human speech is usually 500 to 3,000 Hz.
ear
pathophys
The auditory and vestibular systems both usehair cellsto transduce mechanical forces into action potentials. Hair cells are located in a fluid-filled sensory organ called themembranous labyrinth.There is a labyrinth inside a hollowed-out part of the temporal skull bone on each side of the head.
testing
audiometry
aids in Dx hearing loss and severity of hearing loss
The audiogram tests for hearing loss
The INTENSITY of sound is measured in decibels (dB):
A whisper is about 20 dB.
Loud music (some concerts) is around 80 to 120 dB.
A jet engine is about 140 to 180 dB.
The TONE of sound is measured in cycles per second (cps) or Hertz (Hz):
Low bass tones range around 50 to 60 Hz.
Shrill, high-pitched tones range around 10,000 Hz or higher.
https://www.mountsinai.org/health-library/tests/audiometry
testing
Tympanometry
and contraindications
does the TM move?
Tympanogram test for compliance (movement) of the ear structures
measures the mobility of the ear drum and the small bones in the middle ear
CONTRAINDICATIONS: NEVER DO TYMPANOGRAM ON A PATIENT WITH A BASE OF SKULL FRACTURE OR HEAD TRAUMA!
NEVER DO TYMPANOGRAM ON A PATIENT WHO HAS HAD RECENT EAR SURGERY!
hearing loss
conductive
caused by disorders of the outer and middle ear whereby mechanical transmission of sound to the inner ear is blocked (ear wax perhaps).
defined by the presence of an air-bone gap on audiometry, the difference between air and bone conductuction thresholds.
Hearing loss
sensorineural
caused by disorders of the inner ear (cochlea or auditory neerve) usuallu from damage to the cochlear hair.
Hearing loss
general
Hearing loss is the third most common chronic condition in older Americans after hypertension and arthritis.
Ten percent of the US population (28 million Americans) have some degree of hearing loss.
2 main types: sensorineural and conductive
A 512-Hz tuning fork is useful in differentiating conductive from sensorineural losses.
hearing loss
weber test
In the Weber test, the tuning fork is placed on the forehead or front teeth. In conductive losses, the sound appears louder in the poorer-hearing ear, whereas in sensorineural losses it radiates to the better side.
hearing loss
Rinne test
In the Rinne test, the tuning fork is placed alternately on the mastoid bone and in front of the ear canal. In conductive losses greater than 25 dB, bone conduction exceeds air conduction; in sensorineural losses, the opposite is true.
Conductive Hearing Loss
general
Conductive hearing loss results from external or middle ear dysfunction.
Four mechanisms each result in impairment of the passage of sound vibrations to the inner ear:
(1) obstruction (eg, cerumen impaction),
(2) mass loading (eg, middle ear effusion),
(3) stiffness (eg, otosclerosis)
(4) discontinuity (eg, ossicular disruption).
Conductive losses in adults are most commonly due to cerumen impaction or transient eustachian tube dysfunction from upper respiratory tract infection. Persistent conductive losses usually result from chronic ear infection, trauma, or otosclerosis. Conductive hearing loss is often correctable with medical or surgical therapy, or both.
Sensorineural Hearing Loss
general
Sensory hearing loss results from deterioration of the cochlea, usually due to loss of hair cells from the organ of Corti.
The most common form is a gradually progressive, predominantly high-frequency loss with advancing age (presbycusis)
other causes include excessive noise exposure, head trauma, and systemic diseases.
An individual’s genetic make-up influences all of these causes of hearing loss.
Sensory hearing loss is usually not correctable with medical or surgical therapy but often may be prevented or stabilized. An exception is a sudden sensory hearing loss, which may respond to corticosteroids if delivered within short period after onset.
Hearing loss
more general
Most hearing loss results from presbycusis (getting old). However, prompt evaluation is warranted if the diagnosis is uncertain or if any alarm symptoms are present.
Because patients with gradual hearing loss often do not report this complaint, healthcare providers should take the initiative to ask about it. Patients often ignore or accept hearing loss; alternatively, they may not be as aware of their problem as those around them. Therefore, always include the patient’s family and friends in history taking.
Many patients will not wear hearing aids. Reasons include embarrassment about cosmetic appearance, the stigma associated with using them, cost, and technical difficulty. However, technologic and cosmetic advances in the hearing aid industry may improve patient compliance.
Because several causes of hearing loss are treatable, screening and early detection are important. Don’t be afraid to refer to ENT or audiologist. Every patient who complains of a hearing loss should be referred for audiological evaluation unless the cause is easily treated (eg, cerumen impaction, otitis media).
presbycusis
(getting old)
Gradually progressing high frequency loss with advancing age
Diagnostic Testing
Weber test
Rinne test
Audiometry
Auditory brainstem-evoked responses may differentiate between sensory and neural
sensory hearing loss
Tx
Not correctable with medical therapy
Prevention is key!
Hearing amplification
Unilateral severe sensorineural hearing loss
Stimulate the contralateral cochlea
Cochlear implant
Electronic device implanted into cochlea to stimulate the auditory nerve
sensory hearing loss
Referrals
Refer for audiologic evaluation promptly in new sensorineural hearing loss, unless cause is easily treated (Otitis Media).
hearing loss
screening
Screening recommendations
Age > 65
Prior exposure to high noise levels
Consider repeating every few years
Noise Trauma
general
2nd most common cause of sensory hearing loss
Sound > 85 dB potentially injury the cochlea, especially prolonged exposure
Usually affects high frequencies first
Continued exposure, progresses to involve speech frequencies
Examples:
Industrial machinery
Weapons
Excessively loud music
Concerts
Headphones
Prevention:
Monitoring workplace noise levels
Earplugs
Specially designed earmuffs
hearing loss
Physical trauma
Head trauma
Effects on inner ear similar to severe acoustic trauma
Examples
Airbag deployment
Concussion
Skull fracture
