Objective Tests of the Auditory System SPA 4302

Objective Tests of the Auditory System SPA 4302 Summer 2007

Impedance (Z) vs. Admittance (Y) _______(R) _______(G) Mass Reactance(Xm) Mass Susceptance(Bm) Stiffness Reactance(Xs) Susceptance(Bs) Z = (R 2 + Xt 2)1/2 Y = (G 2 + Bt 2)1/2

Tympanogram: A plot of middle ear admittance as a function of _________ n Pressure is swept from +200 to -200 or 400 d. Pa n Should see peak at point where pressures are _______ n

Tympanogram types: A: peak between +100 and -200 d. Pa: normal n C: peak beyond -200 d. Pa: neg pressure n B: no peak flat tymp: ______ n As: peak but shallow: stiff: _______ n Ad: peak off scale: floppy: _______ n

Tympanogram Types

Static Admittance n A measure of the height of tympanogram peak A As Ad Adults 0. 30 to 1. 70 < 0. 30 >1. 70 3 -10 yrs 0. 25 to 1. 05 < 0. 2 > 1. 05 (All values are in ml of equivalent volume)

The Acoustic Reflex Stapedius contraction measured as change in ______ n Reflex arc: ¨ peripheral ear, ¨__________ ¨Cochlear nucleus ¨__________ ¨Medial Nuclei of VII ¨___________ n

MN 7 7 th CN R L SOC CN CN 8 th IE IE ME ME OE OE MN 7 7 th CN

Clinical Tests using Acoustic Reflexes: n A. R. ______: how intense sound must be to elicit the reflex? n A. R. _____: Is the degree of a contraction maintained throughout a 10 second stimulus?

AR Threshold: to pure-tones, 0. 5, 1, 2, 4 k. Hz n = lowest level at which change in _____ can be read n ipsilaterally or contralaterally n should be between ___ and ___ d. B SL. n

Otoacoustic Emissions (OAE) n Low-level sounds produced by the _______ and recordable in the external ear canal. Spontaneous n Click-evoked n _____ Product n Stimulus _____ n

Recording OAEs

Spectrum of Sound in Ear Canal

OAE as Measure of Cochlear Health

Auditory Evoked Potentials Recording: Comes From: Electrocochleography Cochlea, VIIIth nerve Auditory ____ Response Middle Latency Response _________ Auditory _____ Response Thalamus & _______ cortex Auditory Cortices _____ Hippocampus area

ABR MEASURES I-V IPL Amplitude (μV) I-III I III-V IV III V II Amp V Wave V Latency Time (ms)

Conductive Loss: Curve shifted to higher levels by amount of conductive loss

Severe Cochlear Losses