Reversing Click Polarity May Uncover Auditory Neuropathy In Infants

Abstract

Comparing responses with positive versus negative polarity clicks may help separate ABRs from cochlear potentials and alert clinicians to the possibility of an auditory neuropathy. Therefore, absent or abnormal ABRs in the presence of normal otoacoustic emissions need not always implicate a purely "central disorder," but might be consistent with dysfunction between outer hair cells and primary afferent fibers.

Eletrococleografia extratimpânica na neuropatia/dessincronia auditiva

“…The recording amplitude is increased, compared to ABEP testing, by locating the electrodes closer to the site of origin of cochlear potentials, which is extremely relevant in AN/AD, as published papers have shown that CMs are ampler in such testing conditions. [22][23][24][25][26] Higher quality recordings make it possible to evaluate not only the amplitude but also the duration of CMs; the literature suggests that CMs are more prolonged in AN/AD, compared to normal subjects.…”

“…When OAEs are absent in these patients, however, the differential diagnosis depends on CM recordings. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]20,21 It seems inappropriate to analyze CMs by using ABEP testing for the following reasons: the stimulus (click) that is used to initiate neural potentials limits the conditions for recording CMs; 1,20,25,34 and secondly, many clinicians perform ABEP testing with supra-aural phones,…”

“…20 In the past 10 years, many papers on auditory neuropathy have underlined the role of CMs, which are now analyzed with greater care in AN/AD patients. Reports in the literature have shown that CMs in these patients are more prominent, having an abnormally increased amplitude, [23][24][25][26] and persist for up to 4 to 6 milliseconds after click stimulation, 22 contrary to what is found in normal subjects.…”

“…Furthermore, CMs may be identified by recording auditory evoked potentials using negative and positive polarity acoustic stimuli in which results may be compared, given that CMs are affected by the stimulus polarity, contrary to ABEPs. 1,20,25,34 To confirm the presence of CMs, some researchers block the insertion phone plastic tube to guarantee that recordings are auditory neurophysiological responses that truly reflect acoustic stimulation, rather than electrical artifacts. 3,20,24 Although the literature has suggested that cochlear function is normal in AN/AD, 3,13,34 it is important to analyze CMs in these cases; a number of findings about this specific cochlear potential in AN/AD patients appear to show that the cochlea may be dysfunctional.…”

“…3,20,24 Although the literature has suggested that cochlear function is normal in AN/AD, 3,13,34 it is important to analyze CMs in these cases; a number of findings about this specific cochlear potential in AN/AD patients appear to show that the cochlea may be dysfunctional. [23][24][25][26] The use of ABEP testing of CMs seems inadequate, as CMs cannot be carefully analyzed by this method. A better analysis of CM amplitude and morphology would be obtained with tone bursts, rather than the clicks usually used in ABEP testing.…”