The effects of hypoxia, premature birth, infection, ototoxic drugs, circulatory system and congenital disease on neonatal hearing loss.

OBJECTIVES: To investigate the incidence of neonatal hearing loss in well-baby populations and in a neonatal intensive care unit and to identify potential risk factors for hearing loss in a neonatal intensive care unit which the Joint Committee on Infant Hearing (JCIH) had not recommended.

METHODS: Auditory screening was conducted in 226 infants (452 ears) born in Tohoku University from 2000 to 2001. The cases included 124 healthy newborn infants (248 ears), and 102 newborn infants (204 ears) treated in the neonatal intensive care unit (NICU). Hearing impairment was confirmed through a primary screening of the automated auditory brainstem response (AABR) and a secondary test of the auditory brainstem response (ABR) with otolaryngologic evaluation. Based on these examinations, we divided infants into two groups, 'Pass' and 'Refer'.

RESULTS: Nine patients (15 ears) in Refer group were identified through our protocol. The incidence of the Refer group was 0.8% (1 out of 124) in the well-baby nursery, 7.8% (8 out of 102) in the NICU populations. The infants in Refer group were shown to have a higher incidence of congenital infection (P < 0.01), high C-reactive protein (CRP) (> or =10 mg/dl), chromosomal aberration, and central nervous system abnormality (P < 0.05). On the other hand, there were no statistical differences between the Pass and Refer groups in NICU, birth weight (<2200 g), gestational age, the values of total serum bilirubin, the values of arterial blood gases (pH, PaCO2 , PaO2 ), percutaneous oxygen saturation (SpO2), hemodynamics (blood pressure and heart rate) (P > 0.1). Respiratory status such as the Apgar score (the abbreviation for appearance, pulse, grimace, activity, respiration) (1 min; < or =4), (5 min; < or =6), Silverman retraction score, ototoxic drug use, respiratory distress syndrome (RDS), Meconium aspiration syndrome (MAS), and persistent pulmonary hypertension of newborn (PPHN) were also not statistically related to hearing loss (>0.999).

CONCLUSION: Even in a small number of infants, there are positive relationships between hearing loss and congenital infection, high CRP (> or =10 mg/dl), chromosomal aberration and central nervous system abnormality. The CRP (> or =10 mg/dl) variable are not listed in the high-risk register published by the JCIH, but we can say that the variable may predict hearing impairment in our patient population. The possibility of autosomal recessive inheritance of genes for deafness is supposed when newborns have no other risk factors for hearing loss. This leads us to conclude that hearing screening is an effective way to find out hearing loss population.