Abstract
AIMS: Cochlear synaptopathy, or hidden hearing loss, involves synaptic loss between inner hair cells and auditory nerve fibers. While linked to aging and excessive noise exposure in adults, its impact on neonates remains unclear. This study compared cochlear synaptopathy in full-term neonates hospitalized in the neonatal intensive care unit (NICU) versus healthy controls. METHODS: Sixty full-term neonates-30 hospitalized in the neonatal intensive care unit (NICU) and 30 healthy controls-were enrolled. Inclusion criteria comprised gestational age ≥ 37 weeks, chronological age < 1-month, normal auditory brainstem response (ABR) thresholds (≤ 25 dB nHL), transient evoked otoacoustic emissions, and tympanometry. ABR wave I and V amplitudes, wave I/V ratio, growth functions, acoustic reflex thresholds (ART), and adaptation tests (rapid-rate ABR) were analyzed. RESULTS: No significant differences emerged between NICU-hospitalized and control neonates in ABR wave I/V amplitudes (wave I: 0.05-0.15 µV vs. 0.06-0.11 µV; wave V: 0.12-0.21 µV vs. 0.14-0.20 µV), I/V ratio (0.57-0.75 vs. 0.54-0.67), ART (80.35-73.14 dB HL vs. 78.44-71.59 dB HL), or adaptation latencies (7.60 ms vs. 7.56 ms). CONCLUSION: The results suggest that NICU hospitalization does not significantly increase the risk of cochlear synaptopathy in full-term neonates, even when evaluating synaptic integrity using ABR wave I/V ratios, a biomarker for hidden hearing loss, despite normal hearing thresholds.