Newborn hearing screening at the Neonatal Intensive Care Unit and Auditory Brainstem Maturation in preterm infants

Objectives: Aim of this study is to report and discuss the results of 4 years of Newborn hearing screening (NHS) program at the Neonatal Intensive Care Unit (NICU), particularly evaluating the clinical ABR results.

Methods: Retrospective study. NHS data from NICU newborns, admitted for ≥5 days, in the period from January 1st^, 2013 and December 31st^, 2016, were retrieved and analyzed. NHS results were classified as following: (i) "pass" when both ears for both the a-TEOAE (automated Transient-Evoked Otoacoustic Emissions) and the a-ABR (automated Auditory Brainstem Response) protocol resulted as "pass"; (ii) "fail" when one ear, at either one of the two performed tests resulted as "fail"; (iii) "missing" when the newborns were not tested with both protocols. All "fail" and "missing" newborns were retested (with both tests): in the case of a second "fail" result, a clinical ABR was performed within a period of 3 months.

Results: A total of 1191 newborns were screened. From those, 1044/1191 resulted as "pass", 108/1191 as "fail", and 39/1191 as "missing". During the re-testing of these 147 newborns, 43 were assigned as "missing", 63 were assigned as "pass" (showing bilaterally a wave V identifiable within 30 dB nHL) and 25 failed the retest and/or did not present an identifiable wave V within 30 dB nHL. Among the 147 retested infants, we identified a group of 16 subjects who resulted as NHS "refer" and who, during the audiological follow-up, showed either: (i) a unilateral or bilateral wave V identifiable over 30 dB nHL, at the first clinical ABR assessment; or (ii) a bilateral wave V identifiable within 30 dB nHL, in a following clinical ABR test during the first year of life. These 16 subjects were defined to have an 'Auditory Brainstem Maturation' issue.

Conclusions: A possible "maturation" of the ABR response (and therefore of the auditory pathway) has been hypothesised in 16 out of 1191 infants (1.3%). A delay of the auditory pathway maturation in preterm babies compared to term newborns has already been suggested in the literature. A possible delay of the NHS retest could be considered, in selected cases, with significant savings in economic resources and parental anxiety.