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23 Cards in this Set
- Front
- Back
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acoustic impedance
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gives information regarding TM function and the status of the middle ear. How much sound if being interferred/hampered and how well the ear drum is moving.
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air pump
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air pump enables creating positive or negative air pressure in the ear canal, moving TM in and out
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compliant TM
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absorbs more sound (probe tone)
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stiffer
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reflects more sound
negative pressure in the middle ear TM pulled in toward middle ear also otosclerosis |
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the TM moves best when...
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there is equal pressure on both sides of it.
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fluid
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if the middle ear is filled with fluid, it will not move regardless of pressure. Can't compress/expand fluid.
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microphone in the probe
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measures how much of the probe tone is reflected by the TM as the pressure changes
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flaccid TM
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if one of the ossicle is missing or disconnected from the others
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air tight seal
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cannot get an air tight seal if there is TM perforation
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typanogram
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graphic represenation of TM movement as a function of air pressure exerted upon it in daPa (decapascals)
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Type A
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normal middle ear
greatest compliance (peak) at 0 daPa (atmospheric pressure). large inverted triangle with peak in the rectangle. |
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Type As
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same region of max compliance as A but much shallower (less compliant). normal ME pressure but less compliance due to stapes immobilization (otosclerosis)
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Type AD
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peak of the curve is extremely high with positive and negatives sides of the curve often not meeting. (too much compliance, can indicate separation in the ossicular chain)
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Type B
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flat curve, associated with fluid in the middle ear (MEF) or if wax occludes the tube of the probe. reflects back a consistent mount of probe tone no matter the pressure.
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Type C
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TM is compliant to negative pressure (-100 daPa or more). need to measure as low as -400 daPa. Extremely negative pressure in ME can yield a type B curve at less negative pressures.
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two muscles involved in ME operation
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tensor tympani: role uncertain
stapedius: both contract when loud sound presented to either of both ears at 70-100 dbSL at each frequency |
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stapedial reflex
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85 dBSL (above a person's threshold). involuntary reflex triggered bilaterally even though the stimuli is in one ear.
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acoustic reflex testing
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measures the stapedial reflex. tells us the efficiency with which sound is crossing from one side to the other. automatically adjusts pressure for max compliance. can differentiate cochlear, 8th nerve and brainstem lesions.
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contralateral acoustic reflex testing
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reflex measured in ear opposite to one receiving the tone. if fluid present, reflex may be absent.
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ipsilateral ART
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reflex measured in same ear receiving the tone. if fluid present, reflex may be absent.
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auditory evoked potentials
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does not require voluntary responses. used in newborn hearing screenings. yields audiological and neurological information on auditory pathways through the brainstem
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auditory brainstem responses
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(aka: BSER, BAER) these are computer averaged
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otoacoustic emissions (OAEs)
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ear emissions decrease with greater cochlear damage, not present in hearing loss greater than 40 dB. if absent, they suggest HL but dont know where. they are absent when theres fluid or negative pressure in the ME. If present, does not ensure normal hearing.
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