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SITE OF LESION TESTING

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SITE OF LESION TESTING:
• Distinguishing:
– Sensory (cochlear) from neural (retrocochlear) disorder.
– Different sources of conductive disorder
MEASURES OF SUCCESS:
SENSITIVITY
• Percentage of persons with a disorder who
show up on your test as having that disorder.
• In this application, % of persons with neural
disorder that show a “neural result” on the site
of lesion test.
MEASURES OF SUCCESS:
SPECIFICITY
• percentage of persons without a disorder who
show up on your test as not having that disorder.
• In this application, % of persons with a cochlear
disorder (or no auditory disorder at all) who
show up on your test as not having any neural
disorder.
Loudness Recruitment Tests
• Based on the changes in loudness
perception that accompany different
auditory disorders.
Loudness Growth Patterns
120
100
80
Normal
Cochlear
Retro-cochlear
60
40
20
0
10
30
50
70
Recruitment:
• "Abnormal growth of loudness" or,
persistence of normal loudness above
threshold. More common at higher
frequencies.
Complete: loudness curve meets
normal line
120
100
80
Normal
60
CompleteRecruitm
ent
40
20
0
10 dB
30 dB
50 dB
70 dB
Partial: loudness curve
approaches normal line
120
100
80
Normal
60
Partial
Recruitment
40
20
0
10dB
30 dB
50 dB
70 dB
Hyper- loudness curve crosses
above normal line
120
100
80
Normal
60
Hyperrecruitment
40
20
0
10dB
30 dB
50 dB
70 dB
Recruitment is consistent with
cochlear damage
•
•
•
•
from noise
ototoxic substances
aging
and other causes
Decruitment:
• Abnormal impairment of loudness growth
• loudness curve actually moves away from
normal line
• lack of functioning nerve cells to code
intensity
• associated with retro-cochlear (VIIIth n.)
lesions.
Decruitment
120
100
80
Normal
Decruitment
60
40
20
0
10 dB
30 dB
40 dB
50 dB
100
The Alternate Binaural Loudness
Balance (ABLB)Test
• requires:
• - normal hrg in one ear at freq to be used
• - difference in  between ears > 25 dB
ABLB
• tones pulse alternating between ears 2 or 3
times per judgement.
• pt is asked which ear is louder or same
• - begin at 20 SL in poorer ear,
• - 0 SL in better ear.
• - adjust level in better ear 5 dB steps.
ABLB
• - find level where loudness judged equal.
• - increase poorer ear by 10 or 20 dB and
repeat adjustments in better ear.
PLOTTING ABLB RESULTS:
• Use the “LADDERGRAM”
• Connect decibel values judged equally loud
ABLB SUCCESS?
• Sensitivity = 51%
• Specificity = 88%
The Alternate Monaural LB
(AMLB) Test
• tone alternates between 2 frequencies in the
same ear.
• judgment and procedure is similar to ABLB,
• but comparing "the high pitch versus the
low pitch.”
• generally this is harder for people to do.
Differential Intensity
Discrimination
• The Short Increment Sensitivity Index
(SISI)
• The High Level SISI
The Short Increment Sensitivity
Index
• detection of brief (200 ms) 1 dB-increments
in a 20 SL tone
• 20 trials
• > 70 % = cochlear damage
• < 30 % = other damage or normal
B. High Level SISI
•
•
•
•
at 75 dB HL
Results:
> 70 % = normal or cochlear
< 30 % = retrocochlear
SISI SUCCESS?
• Sensitivity = 68%
• Specificity = 90%
Tone Decay:
• Loss of audibility for a tone that is on
continuously.
• Greater decay is indicative of retrocochlear
problem.
• There are different methods:
Some Tone Decay Tests
• Carhart: begin at 0 SL, up in 5 dB steps
until tone is heard for a full minute
• Olson-Noffsinger: begin at 20 SL, up until
heard for full minute.
Tone Decay Results:
• Type I: no decay: norm, conduct or cochlear
• Type II: heard for longer times as level is
increased: cochlear
• Type III: No growth with increasing level:
retrocochlear
TONE DECAY SUCCESS?
• Sensitivity = 75%
• Specificity = 91%
Bekesy Audiometry:
•
•
•
•
Pt. controls level of tone,
Continuous tone: tone on constantly (C)
Interrupted tone: pulsed on and off (I)
Adaptation should only occur for C, not I
Bekesy Results:
I: C and I overlap: norm or cond.
II: C below I at freqs of HL: Cochlear
III: I follows loss, C drops to bottom: Retro
IV: C below I by 20-25 dB: Coch or Ret
V: I below C: False hearing loss
BEKESY AUDIOMETRY
SUCCESS?
• Sensitivity = 42%
• Specificity = 95%
Acoustic Reflex/ARD Success?
• Sensitivity = 85%
• Specificity = 86%
Auditory Evoked Potentials:
• ABR: within 10 ms of click: Brainstem
disorders.
• EcochG: Meniere's disease
• MLR: Primary auditory cortex: difficult to
pin down.
• Late Cognitive Potentials: processing of
sense info
Auditory Brainstem Response:
•
•
•
•
•
Response within 10 ms of stimulus
waves labeled with Roman numerals
Peaks I, III, and V most useful
Latencies are the key measure
Disorders will produce delays
ABR SUCCESS?
• Sensitivity = 97%
• Specificity = 88%
Middle Latency Response
•
•
•
•
10-80ms
From primary auditory cortex
Highly variable--poor clinical utility
Some correlation to Central Auditory
Processing Disorders
Late Cognitive Potentials
• 80-250 ms
• Processing of sensory information
• From Primary Auditory and Aud.
Association Cortex
• Varies with Attention/Subject wakefulness
P-300
• Obtained in “oddball” task
• Not just auditory
• Reflects Change in Working Memory-“Aha!”
• Changes in latency and amplitude with
variety of disorders
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