audiology in orl

AUDIOLOGY IN ORL

DR. BANDAR MOHAMMED AL-QAHTANI, M.D

KSMC

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Tympanic mem & Ossicular Amplification22:1 in total 1.3:1 maleus to incus (lever action) 17 :1 TM surface to stapes footplateproblem in transmission leads to CHL

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Anatomy of hearing organTHE COCHLEA

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Traveling wave & Tonotopic organization

Traveling wave & Tonotopic organization

High frequency at base and low frequency at apexproblem inside the cochlea transmission leads to SNHL

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Auditory Assessment Clinical vs audiometric tests Clinical : - finger friction - watch test - speech test - tuning fork test

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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

Pure Tone Audiometry Speech Audiometry Acoustic Immittance (impedance test

) Auditory Brainstem Responses Electrocochleography Otoacoustic Emissions

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Pure Tone Audiometry Most common ,subjective test Air conduction testing

Frequencies 125,250,500,1000,2000,4000,8000 HZ

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 Audiometric results are only valid when the

results are actually of the test ear. Interaural attenuation reflects crossover. Air conduction from 40-80dB Bone conduction even at 0dB

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Masking

The audiometric technique used to eliminate responses by the non-test ear.

An appropriate noise is presented to the non-test ear while the test ear is being tested.

Masking level must exceed the non-test ear threshold, but not create crossover.

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Speech Audiometry Determines how well a person hears and

understands speech,subjective test. Spondee words SRT 50% of spondees SRT should be in close correlation with

PTA +- 10 db of PTA. Discrimination score (DS) (90-100% in

normal or conductive DS is 60-70 in sensory hearing loss

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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 Impedance: resistance to acoustic

flow,objective test Admittance: ease of acoustic flow Tested by:

Tympanometry Acoustic Stapedial Reflex

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Tympanometryby 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

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Acoustic Stapedial Reflexto 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 Measures the ability of the stapedius

muscle to maintain sustained contraction.

Lower frequency tone/noise for 10 seconds

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Facial Paralysis 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.

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Eighth nerve lesions 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

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Auditory Brainstem Responses

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.

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Bone Conduction ABR As reliable and repeatable as air

conduction ABR. Particularly useful in structural

abnormalities Canal Atresia or stenosis

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ABR 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 EmissionsLow energy sounds produced by the

cochlear outer hair cells,objective test.

Cochlear amplification. Spontaneous emissions

Not present in greater than 25dB hearing loss.

Evoked Emissions Transient evoked Distorted Product

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OAE and middle ear pathology

Transmission properties of the middle ear directly influence the OAE characteristics. Otitis media Newborns Tympanic membrane perforations

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ANY QUESIONS