Auditory brainstem responses in preterm neonates: maturation and follow-up.

Seventy-five neonatal intensive care unit patients with given auditory brainstem response screening tests at 40 db and 70 db above the normal adult hearing threshold. The presence of wave V, the criterion for pass, was strongly related to postconceptual age: It appeared at 70 db in 50% of the infants tested at 32 weeks' PCA and at 40 db in 50% of the infants tested at 40 weeks' PCA. Forty-four infants failed the last test before NICU discharge (15 at 70 db and 29 at 40 db), but most infants were discharged at a PCA of less than 40 weeks. No significant correlation appeared between ABR test failure and intraventricular hemorrhage, hyaline membrane disease, perinatal asphyxia, hyperbilirubinemia, or aminoglycoside therapy. Follow-up information was obtained in 23 of the 36 "failing" infants who survived (8 died). This consisted of definitive hearing tests in ten patients and historical information supporting normal auditory function in 13 patients. One case of severe hearing loss was confirmed. Thus, most failures of the ABR screen apparently resulted from immaturity. These data raise doubts regarding the effectiveness of ABR screening in the NICU.