Special Testing
1
Site of Lesion
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Cochlear—sensory
Nerve—neural (retrocochlear)
Reliability vs. validity
2
Pure tone and Speech Audiometry
tell us………
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does hearing loss exist
magnitude of the loss
left, right or binaural
type of loss (conductive, sensorineural or
mixed)
3
All hearing tests will turn out either ……
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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
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Sensitivity
Specificity
Its predictive value
Its efficiency
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Immittance
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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
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3 tubes for immittance measures
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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
8
Tympanometry
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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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10
Acoustic Reflex
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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)
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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)
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Spontaneous Otoacoustic Emissions
(SOAE’s) - when the cochlea produces
sounds in the absence of external stimuli
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OAE (continued)
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Evoked Otoacoustic Emissions (EOAE’s) occurs
during or immediately following acoustic stimulation.
There are several types of EOAE’s:
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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
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Recruitment
Hyper-recruitment
Derecruitment
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Test for Recruitment
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Alternate Binaural Loudness Balance (ABLB)
test/laddergram
Short Increment Sensitivity Index (SISI
19
Tone Decay
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60 second method
2 minute method
20
Bekesy Audiogram
21
Bekesy Tracings
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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)
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