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Special Testing

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Site of Lesion

Cochlear—sensory Nerve—neural (retrocochlear) Reliability vs. validity

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Pure tone and Speech Audiometry tell us………

does hearing loss exist magnitude of the loss left, right or binaural type of loss (conductive, sensorineural or

mixed)

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All hearing tests will turn out either …… true positive = within normal limits (wnl) true negative = test eliminates anatomical

area as cause of loss false positive = the test indicates lesion site

incorrectly false negative = the test incorrectly

eliminated an anatomical area as the cause of the loss

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Audiologic Tests for Site of Lesion

Sensitivity Specificity Its predictive value Its efficiency

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Immittance Static Compliance - mobility of the tympanic

membrane with a given value of pressure in the external auditory meatus

Tympanometry - a measurement of middle ear pressure determined by the mobility of the membrane as a function of different amounts of positive and negative air pressure in the external ear canal

Acoustic Reflex - contraction of the middle ear muscles due to intense sounds. Acoustic reflex occurs at 70 - 100 dB (SL) in normals, with 85 dB(SL) as mean

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Immitance Instrumentation

3 tubes for immittance measures miniature loudspeaker which emits 220 or 226 Hz

(incident wave) miniature microphone which picks up sound in the

external ear canal (reflected and incident wave) air pump for positive and negative pressure in

external ear canal Regular earphone on contralateral ear

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Immittance Meter

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Tympanometry

Type A = normal Type As = otosclerosis Type Ad = ossicular chain disarticulation Type B = flat—fluid in middle ear Type C = negative pressure --100 or more

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Acoustic Reflex

When an intense sound is introduced to either or both ears the stapedius muscle in both ears contracts causing both TM’s to stiffen

The signal used to illicit the reflex is called the RAS (reflex activating stimulus and can be made by any kind of sound)

Acoustic Reflex Threshold (ART) - the lowest level at which an acoustic reflex can be obtained

Acoustic Reflex Decay—abnormally fast decay (relaxation) of the stapedius muscle as the intense sound continues (lesions of the VIII nerve and parts of the brain stem. Tone presented at 10 dB above ART for 10 seconds. Done at 500 and 1,000 Hz only (3—5 seconds = VIII nerve problem)

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Auditory Evoked Potentials (AEP’s)

Electrocochleography (EcoG) The procedure for studying the neuro-electric events resulting from when an acoustic stimuli activates the inner ear

Auditory evoked potentials are the electrical responses to the sound stimuli. Latency = the time between the introduction of a stimulus and the occurrence of the response

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Instrumentation for Evoked Potentials

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Auditory Brain Stem Audiometry

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Brain-stem Evoked Potentials

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Otoacoustic Emissions (OAE)

Spontaneous Otoacoustic Emissions (SOAE’s) - when the cochlea produces sounds in the absence of external stimuli

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OAE (continued)

Evoked Otoacoustic Emissions (EOAE’s) occurs during or immediately following acoustic stimulation. There are several types of EOAE’s:

Transient Evoked Otoacoustic Emissions (TEOAE’s) produced by brief acoustic stimuli

Distortion Product Otoacoustic Emissions (DPOAE’s) results from inner ear distortion generated when two or more tones of different frequencies are introduced into the ear

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Loudness Recruitment

Recruitment Hyper-recruitment

Derecruitment

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Test for Recruitment

Alternate Binaural Loudness Balance (ABLB) test/laddergram

Short Increment Sensitivity Index (SISI

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Tone Decay

60 second method 2 minute method

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Bekesy Audiogram

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Bekesy Tracings

Type I = normal Type II = cochlear (cont. drops up to 20 dB

lower than pulsed after 1,000 Hz Type III = retrocochlear lesions (cont. drop

immediately) Type IV = retrocochlear (cont. drop before

500 Hz) Type V = Pseudohypacusis (pulsed drop

below continuous tones)