Presentation on theme: "SITE OF LESION TESTING:"— Presentation transcript:
1 SITE OF LESION TESTING: Distinguishing:Sensory (cochlear) from neural (retro-cochlear) disorder.Different sources of conductive disorder
2 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.
3 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.
4 Loudness Recruitment Tests Based on the changes in loudness perception that accompany different auditory disorders.
10 Recruitment is consistent with cochlear damage from noiseototoxic substancesagingand other causes
11 Decruitment: Abnormal impairment of loudness growth loudness curve actually moves away from normal linelack of functioning nerve cells to code intensityassociated with retro-cochlear (VIIIth n.) lesions.
13 The Alternate Binaural Loudness Balance (ABLB)Test requires:- normal hrg in one ear at freq to be used- difference in between ears > 25 dB
14 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.
15 ABLB - find level where loudness judged equal. - increase poorer ear by 10 or 20 dB and repeat adjustments in better ear.
16 PLOTTING ABLB RESULTS: Use the “LADDERGRAM”Connect decibel values judged equally loud
18 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.
19 Differential Intensity Discrimination The Short Increment Sensitivity Index (SISI)The High Level SISI
20 The Short Increment Sensitivity Index detection of brief (200 ms) 1 dB-increments in a 20 SL tone20 trials> 70 % = cochlear damage< 30 % = other damage or normal
21 B. High Level SISI at 75 dB HL Results: > 70 % = normal or cochlear < 30 % = retrocochlear
22 SISI SUCCESS?Sensitivity = 68%Specificity = 90%
23 Tone Decay: Loss of audibility for a tone that is on continuously. Greater decay is indicative of retrocochlear problem.There are different methods:
24 Some Tone Decay TestsCarhart: begin at 0 SL, up in 5 dB steps until tone is heard for a full minuteOlson-Noffsinger: begin at 20 SL, up until heard for full minute.
25 Tone Decay Results: Type I: no decay: norm, conduct or cochlear Type II: heard for longer times as level is increased: cochlearType III: No growth with increasing level: retrocochlear
26 TONE DECAY SUCCESS?Sensitivity = 75%Specificity = 91%
27 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
28 Bekesy Results: I: C and I overlap: norm or cond. II: C below I at freqs of HL: CochlearIII: I follows loss, C drops to bottom: RetroIV: C below I by dB: Coch or RetV: I below C: False hearing loss
31 Auditory Evoked Potentials: ABR: within 10 ms of click: Brainstem disorders.EcochG: Meniere's diseaseMLR: Primary auditory cortex: difficult to pin down.Late Cognitive Potentials: processing of sense info
32 Auditory Brainstem Response: Response within 10 ms of stimuluswaves labeled with Roman numeralsPeaks I, III, and V most usefulLatencies are the key measureDisorders will produce delays