Transcript 4-Auditory-function-slides-2004

AUDIOLOGY IN ORL
and deafness
DR. BANDAR MOHAMMED ALQAHTANI, M.D
KSMC
Tympanic mem & Ossicular Amplification
22:1 in total
1.3:1 maleus to incus (lever action)
17 :1 TM surface to stapes footplate
problem in transmission leads to CHL
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Anatomy of hearing organ
THE COCHLEA
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Traveling wave & Tonotopic organization
High frequency at base and low frequency at apex
problem inside the cochlea transmission OR nerve transmission
lead to SNHL
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-so hearing loss can be divided into
Conductive vs SNHL
-both can be congentally/developmental vs aquired
-aquired :TINDM OVA
-congenital –---
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Auditory Assessment
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Clinical vs audiometric tests
Clinical :
- finger friction
- watch test
- speech test
- tuning fork test
Audiometric tests :
 subjective vs objective tests
- pure tone audiometry
- speech audiometry
- impedance audiometry
a-tympanometry
b-acoustic reflex
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Anatomy
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Audiometric Assessment
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Pure Tone Audiometry
Speech Audiometry
Acoustic Immittance (impedance test )
Auditory Brainstem Responses
Electrocochleography
Otoacoustic Emissions
Pure Tone Audiometry
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Most common ,subjective test
Air conduction testing
Frequencies 125,250,500,1000,2000,4000,8000 HZ
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Bone conduction testing
250,500,1000,2000,4000 HZ
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Pure tone audiometry
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USES
As baseline test (pre op and post op)
To differentiate the conductive vs sensorineural pathway
The degree of handicap or heaing loss and which frequencies
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Crossover
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Audiometric results are only valid when the results are
actually of the tested ear.
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Interaural attenuation reflects crossover.
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Air conduction from 40-80dB
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Bone conduction
even at 0dB
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Masking
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The audiometric technique used to eliminate responses by
the non-test ear.
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An appropriate noise is presented to the non-test ear while
the test ear is being tested.
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Masking level must exceed the non-test ear threshold, but
not create crossover.
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Speech Audiometry
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Determines how a well person hears and understands
speech,subjective test.
Speech reception threshold SRT
SRT 50% of spondees
SRT should be in close correlation with PTA +- 10 db
of PTA.
Discrimination score (DS) 30-40 db above PTA
90-100% in normal or conductive
DS is 60-70 in sensory hearing loss
DS -(normal ,CHL, COCHLEAR &RETROCOCH ROLLOVER )
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USES
-malingerer patients
-for fitting Hearing Aids
-for cochlear implant patients
-to differentiate cochlear than retro-cochlear lesion
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Acoustic Immittance
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Impedance: resistance to acoustic flow,objective
test
Admittance: ease of acoustic flow
Tested by:
Tympanometry
 Acoustic Stapedial Reflex
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Tympanometry
by Jerger
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A
normal between 100-(-100)
As stiff type otosclerosis or stiff TM.
Ad flaccid type ossicular discontinuity
B
flat –fluid in ME or thick TM
C
more in negative –retracted TM
Acoustic Stapedial Reflex
to elicit a stapedial muscle contraction, objective
test.
 3 primary acoustic reflex characteristics
Presence or absence of the reflex
 Reflex threshold
 Reflex Decay
 It tests VIII,brain stem ,VII
 Good for screening in infants and malingerer
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Acoustic Reflex Decay
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Measures the ability of the stapedius muscle to
maintain sustained contraction.
Lower frequency tone/noise for 10 seconds
Facial Paralysis
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Absent or abnormal stapedial reflex when the
recording probe is ipsilateral to the side of the
lesion.
Can also be helpful in locating lesions proximal
or distal to the stapedial muscle.
Eighth nerve lesions
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Absent reflexes when stimuli is presented to the
affected ear.
Reflexes in eighth nerve lesions are not
dependent on the degree of hearing loss.
Rapid reflex decay
Auditory Brainstem Responses
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Impulses that are generated by the auditory
neural pathway that can be recorded on the
scalp.
objective test
Not affected by sleep, sedation, or attention.
Bone Conduction ABR
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As reliable and repeatable as air conduction
ABR.
Particularly useful in structural abnormalities
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Canal Atresia or stenosis
ABR
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Primary goal is a clear and reliable Wave I
Wave I : distal 8th nerve
 Wave II : proximal 8th nerve
 Wave III : cochlear nuclei
 Wave IV : SOC
 Wave V : Lateral Lemniscus
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ABR
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Otoacoustic Emissions
Low energy sounds produced by the cochlear
outer hair cells,objective test.
 Cochlear amplification.
 Spontaneous emissions
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Not present in greater than 25dB hearing loss.
Evoked Emissions
Transient evoked
 Distorted Product
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OAE and middle ear pathology
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Transmission properties of the middle ear
directly influence the OAE characteristics.
Otitis media
 Newborns
 Tympanic membrane perforations
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ANY QUESIONS
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