Temporal processing in the auditory brainstem response by full-term 6-week- and 9-month-old infants

Change to Hearing Loss-Related Risks and Screening in Preterm Infants

Hearing loss is one of the most common congenital defects in infancy; it increases speech and language delays and adversely affects academic achievement and socialemotional development. The risk of hearing loss in premature infants is higher than that in normal newborns, and because of the fragility of the auditory nervous system, it is more vulnerable to different risk factors. The hearing screening guidelines in current use were proposed by the American Academy of Pediatrics and updated in 2007, but there are no uniform guidelines for hearing screening in preterm infants. This review focuses on the risk factors related to hearing loss in premature infants, hearing screening strategies, and reasons for failure. The aim is to provide a more comprehensive understanding of hearing development in preterm infants to achieve early detection and early intervention. At the same time, attention should be paid to delayed auditory maturation in preterm infants to avoid excessive intervention. KEY POINTS: · Hearing loss is very common in infancy, especially in premature infants.. · Genetic factors, infection, hyperbilirubinemia, drugs, and noise are the main causes.. · We should pay attention to the delayed hearing maturity of premature infants and avoid excessive intervention..

Prenatal exposure to multiple pesticides is associated with auditory brainstem response at 9months in a cohort study of Chinese infants

BACKGROUND

Pesticides are associated with poorer neurodevelopmental outcomes, but little is known about the effects on sensory functioning.

METHODS

Auditory brainstem response (ABR) and pesticide data were available for 27 healthy, full-term 9-month-old infants participating in a larger study of early iron deficiency and neurodevelopment. Cord blood was analyzed by gas chromatography-mass spectrometry for levels of 20 common pesticides. The ABR forward-masking condition consisted of a click stimulus (masker) delivered via ear canal transducers followed by an identical stimulus delayed by 8, 16, or 64 milliseconds (ms). ABR peak latencies were evaluated as a function of masker-stimulus time interval. Shorter wave latencies reflect faster neural conduction, more mature auditory pathways, and greater degree of myelination. Linear regression models were used to evaluate associations between total number of pesticides detected and ABR outcomes. We considered an additive or synergistic effect of poor iron status by stratifying our analysis by newborn ferritin (based on median split).

RESULTS

Infants in the sample were highly exposed to pesticides; a mean of 4.1 pesticides were detected (range 0-9). ABR Wave V latency and central conduction time (CCT) were associated with the number of pesticides detected in cord blood for the 64ms and non-masker conditions. A similar pattern seen for CCT from the 8ms and 16ms conditions, although statistical significance was not reached. Increased pesticide exposure was associated with longer latency. The relation between number of pesticides detected in cord blood and CCT depended on the infant's cord blood ferritin level. Specifically, the relation was present in the lower cord blood ferritin group but not the higher cord blood ferritin group.

CONCLUSIONS

ABR processing was slower in infants with greater prenatal pesticide exposure, indicating impaired neuromaturation. Infants with lower cord blood ferritin appeared to be more sensitive to the effects of prenatal pesticide exposure on ABR latency delay, suggesting an additive or multiplicative effect.