Redução do limiar de reflexo acústico em neonatos sem risco auditivo

Abstract

The auditory sensitization, a tool used in the investigation of acoustic reflex, allows the decrease of acoustic reflex thresholds from a facilitating stimulus. It may be presented before or simultaneously with the elicitor tone. The thresholds after and before the facilitating stimulus are compared and it is expected to see the decreased threshold. From the study of the acoustic reflex it is possible to obtain information about the auditory pathways, such as structures of the brainstem, since the acoustic reflex pathway is related to the auditory nuclei in this site. They are also involved in auditory processing. Thus, alterations of the acoustic reflex could be related to deficits in auditory processing skills. Aim: This study aims at investigating the acoustic reflex sensitization from a highfrequency facilitating tone (6 kHz) in newborns without risk factors to hearing impairment. Results: The acoustic reflex threshold decreased in males and females for all studied frequencies. Conclusion: A high-frequency facilitating tone presented simultaneously produced a decrease of the acoustic reflex threshold in newborns without risk factors to hearing impairment.

Acoustic reflex on newborns: the influence of the 226 and 1,000 Hz probes

“…In this study, for newborns in Group I, the mean ASRT obtained with the 226 Hz probe was lower (Table 1) in all frequencies in comparison to that found by other studies (14,24) . With the 1,000 Hz probe, the average was 74.2 dB for the 1,000 Hz frequency and 62.9 dB for 2,000 Hz (Table 1).…”

“…The reflexes were detected more successfully among infants when the correlation was calculated in 1,000-8,000 Hz, and among adults, from 250 to 2,000 Hz. The ipsilateral reflex threshold was analyzed (14) in the 1,000, 2,000, and 4,000 Hz frequencies, with the 226 Hz probe, and it was observed that for the female gender and the right ear, the mean dB (±standard deviation) was 96. 43 There was no significant difference between gender and frequency.…”

“…The acoustic reflex is defined as the lowest stimulus intensity able to produce a detectable change in acoustic admittance (5,6,10) . The analysis of the presence or absence of Acoustic Stapedial Reflex Threshold (ASRT) may indicate a middle-ear dysfunction, significant cochlear hearing loss, retrocochlear pathology, or dysfunction in the facial nerve (11)(12)(13)(14) . The results of the acoustic reflex also help to interpret the audiological findings after verifying the compatibility between diagnostic tests (15) .…”

Estudo das medidas de imitância acústica com tom sonda de 226 e 1000 Hz em neonatos

“…The acoustic reflexes involve auditory nuclei of the encephalic trunk, which relate to auditory processing skills. Acoustic reflex alterations may, therefore, indicate an alteration in one of these nuclei and, consequently, in auditory processing skills such as locating, selective attention and speech with background noise (10) .…”

“…Starting from the considerations made above, we emphasize the need to carry on more tympanometry researches in neonates making use of both test conditions (226 e 1000 Hz). It is possible to research the thresholds of the acoustic reflexes in beast-fed babies, or even in the neonatal period, and, therefore, obtain information about the auditory pathways (10,15) . In literature there are studies which demonstrate the presence of contralateral acoustic reflex in neonates (20) , while there are others which demonstrate the presence of ispilateral acoustic reflex in breast-fed babies (6,21,22) .…”