Special Testing

1. Special Testing

2. Site of Lesion • Cochlear—sensory • Nerve—neural (retrocochlear) • Reliability vs. validity

3. Pure tone and Speech Audiometry tell us……… • does hearing loss exist • magnitude of the loss • left, right or binaural • type of loss (conductive, sensorineural or mixed)

4. All hearing tests will turn out either …… • true positive = within normal limits (wnl) • true negative = test eliminates anatomical area as cause of loss • false positive = the test indicates lesion site incorrectly • false negative = the test incorrectly eliminated an anatomical area as the cause of the loss

5. Audiologic Tests for Site of Lesion • Sensitivity • Specificity • Its predictive value • Its efficiency

6. Immittance • Static Compliance - mobility of the tympanic membrane with a given value of pressure in the external auditory meatus • Tympanometry - a measurement of middle ear pressure determined by the mobility of the membrane as a function of different amounts of positive and negative air pressure in the external ear canal • Acoustic Reflex - contraction of the middle ear muscles due to intense sounds. Acoustic reflex occurs at 70 - 100 dB (SL) in normals, with 85 dB(SL) as mean

7. Immitance Instrumentation • 3 tubes for immittance measures • miniature loudspeaker which emits 220 or 226 Hz (incident wave) • miniature microphone which picks up sound in the external ear canal (reflected and incident wave) • air pump for positive and negative pressure in external ear canal • Regular earphone on contralateral ear

8. Immittance Meter

9. Tympanometry • Type A = normal • Type As = otosclerosis • Type Ad = ossicular chain disarticulation • Type B = flat—fluid in middle ear • Type C = negative pressure --100 or more

11. Acoustic Reflex • When an intense sound is introduced to either or both ears the stapedius muscle in both ears contracts causing both TM’s to stiffen • The signal used to illicit the reflex is called the RAS (reflex activating stimulus and can be made by any kind of sound) • Acoustic Reflex Threshold (ART) - the lowest level at which an acoustic reflex can be obtained • Acoustic Reflex Decay—abnormally fast decay (relaxation) of the stapedius muscle as the intense sound continues (lesions of the VIII nerve and parts of the brain stem. Tone presented at 10 dB above ART for 10 seconds. Done at 500 and 1,000 Hz only (3—5 seconds = VIII nerve problem)

12. Auditory Evoked Potentials (AEP’s) • Electrocochleography (EcoG) The procedure for studying the neuro-electric events resulting from when an acoustic stimuli activates the inner ear • Auditory evoked potentials are the electrical responses to the sound stimuli. Latency = the time between the introduction of a stimulus and the occurrence of the response

13. Instrumentation for Evoked Potentials

14. Auditory Brain Stem Audiometry

15. Brain-stem Evoked Potentials

16. Otoacoustic Emissions (OAE) • Spontaneous Otoacoustic Emissions (SOAE’s) - when the cochlea produces sounds in the absence of external stimuli

17. OAE (continued) • Evoked Otoacoustic Emissions (EOAE’s) occurs during or immediately following acoustic stimulation. There are several types of EOAE’s: • Transient Evoked Otoacoustic Emissions (TEOAE’s) produced by brief acoustic stimuli • Distortion Product Otoacoustic Emissions (DPOAE’s) results from inner ear distortion generated when two or more tones of different frequencies are introduced into the ear

18. Loudness Recruitment • Recruitment • Hyper-recruitment • Derecruitment

19. Test for Recruitment • Alternate Binaural Loudness Balance (ABLB) test/laddergram • Short Increment Sensitivity Index (SISI

20. Tone Decay • 60 second method • 2 minute method

21. Bekesy Audiogram

22. Bekesy Tracings • Type I = normal • Type II = cochlear (cont. drops up to 20 dB lower than pulsed after 1,000 Hz • Type III = retrocochlear lesions (cont. drop immediately) • Type IV = retrocochlear (cont. drop before 500 Hz) • Type V = Pseudohypacusis (pulsed drop below continuous tones)