[Changes in transient evoked otoacoustic emissions contralateral suppression in infants].
BACKGROUND
It has been suggested that the function of the medial olivocochlear system (MOCS) can be evaluated by the suppression effect of the transient evoked otoacoustic emission (TEOAE). The competitive noise has an inhibitory effect on the functioning of the outer hair-cell, reducing the level of otoacoustic emissions. Despite the fact that there is no postnatal growth of the cochlea, middle ear growth and auditory processing development continue after birth.


OBJECTIVE
To analyze age-related changes of MOCS using the TEOAE suppression in healthy infants.


METHODS
25 full-term infants with no risk factors for hearing loss were evaluated in two moments: at birth and at the age of six months. At both ages TEOAE were recorded in the "Quickscreen" mode, nonlinear stimulation at 78dB peSPL, for both ears, with and without contralateral noise presented at 60dB SPL.


RESULTS
The data analyses, using ANOVA, revealed significant contralateral suppression of otoacoustic emissions in both groups, but the TEOAE levels and the amount of TEOAE contralateral suppression were smaller at six-month of age when compared to the neonatal period (p < 0.01). The TEOAE suppression effect for neonatals was 2.81dB (+/- 0.19dB) and at the age of six months was 1.41dB (+/- 0.29dB).


CONCLUSIONS
The amount of TEOAE suppression decreased from birth to six months of age. The association between contralateral acoustic stimulation and a commercially available rapid TEOAE measurement system enables a non-invasive monitoring of the auditory efferent mechanism and seems to be clinically feasible to evaluate cochlear status and auditory efferent function development in infants at risk.
Durante
Alessandra Spada
AS
Curso de Fonoaudiologia da Faculdade de Ciências Médicas da Santa Casa de São Paulo. asdurant@usp.br
Carvallo
Renata Mota Mamede
RM
D000161:Acoustic Stimulation / Q000379:methods / Q000592:standards; D017677:Age Distribution; D000704:Analysis of Variance; D001299:Audiometry / Q000379:methods* / Q000592:standards; D003051:Cochlea / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology*; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009847:Olivary Nucleus / Q000502:physiology*; D017084:Otoacoustic Emissions, Spontaneous; D017678:Sex Distribution