Subjective interference is present in:
Correct Answer: Pure tone audiometry
Description: Ans: A (Pure tone audiometry) Ref: Dhingra page 27Explanation:PTA is subjective test.Impedance audiometry, OAE and BERA are objective tests.Otoacoustic Emission (OAE)OAE are low intensity sounds produced by the outerhair cells of a normal cochlea.Sedation does not affect OAE.Types are:Spontaneous OAE - Healthy individuals with hearing loss < 30 dB.Evoked OAE - Elicited by a sound stimulus and are of the following type:i. Transient evoked OAE (TEOAE)- evoked by clicks.ii. Distortion product OAE (DPOAE) - two tones are simultaneously presented to the cochlea to produce distortion products.UsesScreening test of hearing in neonatesDifferentiate between a cochlear and retro- cochlear lesionOAE may be absent in:50% of normal populationLesions of the cochleaMiddle ear disordersHearing loss > 30 dBBERA - Brainstem Evoked Response AudiometryAlso called BAER or BAEP or ABR (auditory brainstem response)In this electric potentials are generated in response to several click stimuli or tone hursts and picked up from the vertex by surface electrodesTests the integrity of central auditory pathwayNon invasive testNormally 7 waves are seen in the first 10 millisecondsI, III and V waves are most importantAbsolute latency, inter wave latency and the amplitude of the waves is measuredSite for generation of weaves areWave I - distal CN VIIIWave II - proximal CN VIIIWave III - cochlear nucleusWave IV - superior olivary complexWave V - lateral lemniscusWave VI and VII - inferior colliculusUsesScreening for hearing in infantsThreshold estimation in infantsTo diagnose retro cochlear pathology and brainstem lesionsMonitor VIII N in surgery of acoustic neuroma
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