Presentation on theme: "SITE OF LESION TESTING: Distinguishing: –Sensory (cochlear) from neural (retro- cochlear) disorder. –Different sources of conductive disorder."— Presentation transcript:
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.
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.
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
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
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