Assessment of hearing organ activity in a group of neonates with central nervous system impairment

The effect of peri-intraventricular hemorrhage on the auditory pathway of infants

OBJECTIVE

To verify the effect of peri-intraventricular hemorrhage on the auditory pathway of preterm infants.

METHOD

It is a non-concurrent cohort study. This study was conducted in a tertiary public. Preterm infants with peri-intraventricular hemorrhage comprised the study group, and preterm infants without peri-intraventricular hemorrhage were included as a comparison group, both were similar in relation to gestational age and risk indicators for hearing loss. Participants had to meet the following inclusion criteria: have been born at the study site, presence of otoacoustic emissions by transient stimulus in both ears and brainstem auditory evoked potentials with all components bilaterally identified.

RESULTS

44 infants with an average age of 3 months with peri-intraventricular hemorrhage and 2,6 months without peri-intraventricular hemorrhage met the inclusion criteria. Regarding the brainstem auditory evoked potentials results, a significant increase was observed in absolute latency values of waves I, III and V, as well as in the interpeak intervals I-III and I-V, bilaterally, in infants with peri-intraventricular hemorrhage.

CONCLUSION

This study concluded that infants with peri-intraventricular hemorrhage presented a delay in the neural conduction of sound, which justifies the monitoring of the auditory function in these infants during the period of language development.

Chronic prenatal hypoxia impairs cochlear development, a mechanism involving connexin26 expression and promoter methylation

Chronic prenatal hypoxia is a damaging to fetal development and may have various consequences, including hearing loss. Connexin 26 (Cx26) is one of the major protein subunits required for gap junction formation, and has an important role in maintaining homeostasis in the cochlea and normal hearing. Cx26 mutation and expression abnormality are closely associated with inherited nonsyndromic deafness, but the association between Cx26 and prenatal hypoxia is less established. The present study aimed to examine Cx26 expression and aberrant methylation the Cx26 promoter region in the cochlea from rats exposed to chronic prenatal hypoxia. Hematoxylin and eosin staining demonstrated that the number of hair cells in the organ of Corti were less in the hypoxia group. Reverse transcription-quantitative polymerase chain reaction and western blot analysis revealed that protein and mRNA levels of Cx26 were decreased in the hypoxia group compared with the control group. Further bisulfite sequencing analysis revealed that prenatal hypoxia significantly increased the methylation status of the promoter region of the Cx26 gene. These results demonstrate that chronic prenatal hypoxia caused hearing impairment, and suggest that promoter region hypermethylation and expression downregulation of Cx26 underlie the mechanism of action.

The effects and outcomes of electrolyte disturbances and asphyxia on newborns hearing

OBJECTIVE

To determine the effect of electrolyte disturbances (ED) and asphyxia on infant hearing and hearing outcomes.

STUDY DESIGN

We conducted newborn hearing screening with transient evoked otoacoustic emission (TEOAE) test on a large scale (>5000 infants). The effects of ED and asphyxia on infant hearing and hearing outcomes were evaluated.

RESULT

The pass rate of TEOAE test was significantly reduced in preterm infants with ED (83.1%, multiple logistic regression analysis: P<0.01) but not in full-term infants with ED (93.6%, P=0.41). However, there was no significant reduction in the pass rate in infants with asphyxia (P=0.85). We further found that hypocalcaemia significantly reduced the pass rate of TEOAE test (86.8%, P<0.01). In the follow-up recheck at 3 months of age, the pass rate remained low (44.4%, P<0.01).

CONCLUSION

ED is a high-risk factor for preterm infant hearing. Hypocalcaemia can produce more significant impairment with a low recovery rate.