SITE OF LESION TESTING:
• Distinguishing:
– Sensory (cochlear) from neural (retro-cochlear) 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
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Normal
Cochlear
Retro-cochlear
Recruitment:
• "Abnormal growth of loudness" or, persistence of normal loudness above threshold. More common at higher frequencies.
Complete: loudness curve meets normal line
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Normal
CompleteRecruitment
Partial: loudness curve approaches normal line
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Normal
PartialRecruitment
Hyper- loudness curve crosses above normal line
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Hyper-recruitment
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
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NormalDecruitment
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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