[Normal parameters of ear acoustic emissions in neonates]. / Parámetros de normalidad de las otoemisiones acústicas en neonatos.

INTRODUCTION: The ear acoustic emissions (EAE) are produced from pure low intensity tones coming from the cochlea in response to a stimulus. Hypocusia in the neonate may be detected by universal hearing screening programs using EAE that have a sensitivity of 91% and specificity of 85%. OBJECTIVE: To define the normal limits we measured the EAE in a group of healthy newborns and calculated the media and standard deviation (SD). PATIENTS AND METHODS: We enrolled 280 healthy neonates, previous external ear evaluation for permeability and we measured the EAE at 7 to 30 days of life at 2000, 2500, 3187, 4000, 5062 y 6375 Hz, using a 55-65 dB stimulus for each frequency band. RESULTS: In each frequency band evaluated we calculated the media: 10.76, 9.16, 9.46, 7.89, 4.83, 2 dB SPL, and minus two SD: 0.54, -0.33, 0.06, -2.04, -4.37, -7.43 dB SPL, that we considered the lower limit of normality for both ears in each frequency band tested. There were no significant differences between measurements in both ears (p>0.05). CONCLUSIONS: The EAE measurement is an easy, and low cost test that can be used to make the universal hearing screening accessible. These results support the normal levels of EAE and the Corti organ function in healthy newborns.

[Hearing screening and diagnosis of hearing loss: high risk versus low risk neonates]. / Tamizaje y confirmación diagnóstica de hipoacusia. Neonatos de alto riesgo versus población abierta.

INTRODUCTION: congenital hearing loss is a serious health problem affecting 1 to 3 out of 1000 neonates, and is the most common cause of neurosensorial defect; hearing screening helps to identifying early permanent childhood hearing loss (HL). OBJECTIVE: to establish the percentage of hearing loss in newborns with and without risk factors through hearing screening. MATERIAL AND METHODS: by using a cross-sectional design, a group of neonates with risk factors and a group without risk factors were included in a two-stage hearing screening program. The otoacoustic emissions (OAEs) procedure was done in the first stage and the automated auditory brain stem response (AABR) procedure in the second stage. The latter was performed only in children with abnormal results in the OAE procedure. RESULTS: 518 newborns were included in the hearing screening procedures; 220 neonates with risk factors and 298 without risk factors. 35 had + OAE test and the ABBR procedure helped to confirm that 30 neonates had hearing loss, 26 had bilateral HL; 10 had asymmetric HL; 4 had unilateral HL and 5 were false positives. The AABR procedure ascertained 17 HL cases with a threshold > 40 dB (86 per 100,000), 11 cases (55 per 100,000) in the risk group and 6 (30 per 100,000) in the non-risk group (p < 0.05). The main risk factors were prematurity, craniofacial anomalies, mechanical ventilation, prescription of amikacin and cytomegalovirus infection. CONCLUSIONS: the two-stage hearing screening program ascertained that 5.7 % had HL. AABR (threshold > 40 dB) confirmed 17 (86 per 100,000) neonates with HL, which was more frequent in the risk group (5 %) than in the non-risk group (2 %; p < 0.05).