Auditory brainstem response morphology and analysis in very preterm neonatal intensive care unit infants.

OBJECTIVES/HYPOTHESIS Analysis of auditory brainstem response (ABR) in very preterm infants can be difficult owing to the poor detectability of the various components of the ABR. We evaluated the ABR morphology and tried to extend the current assessment system. STUDY DESIGN Prospective cohort study. METHODS We included 28 preterm very low birth weight infants admitted to the neonatal intensive care unit of Sophia Children's Hospital. ABRs were measured between 26 and 34 weeks postconceptional age. The presence of the following ABR parameters was recorded: the ipsilateral peaks I, III and V, the contralateral peaks III and V, and the response threshold. RESULTS In 82% of our population, a typical "bow tie" response pattern was present as a sign of early auditory development. This bow tie pattern is the narrowest part of the response wave and is predominantly characterized by the ipsilateral negative peak III. This effect may be emphasized by the contralateral peak III. The bow tie pattern is seen approximately 0.1 milliseconds before the ipsilateral peak III. From 30 weeks postconceptional age onward, a more extensive morphologic pattern is recorded in 90% of the infants. A flow chart was designed to analyze the ABR morphology of preterm infants in an unambiguous stepwise fashion. CONCLUSIONS A typical bow tie pattern preceding peak III seems to be the earliest characteristic of the developing ABR morphology in preterm infants. As ABR characteristics will improve with increasing age, neonatal hearing screening should be postponed until after 34 weeks.