SITE OF LESION TESTING: Distinguishing: –Sensory (cochlear) from neural (retro- cochlear)...

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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Normal

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