Frequency-Following Response and Auditory Behavior in Children with Prenatal Exposure to the Zika Virus

Introduction Prenatal exposure to the Zika virus can impair neurodevelopment and cause auditory damage. Objective To analyze the frequency-following response (FFR) and the auditory behavior (with the LittlEars ® questionnaire) of children with and without prenatal exposure to Zika virus infection. Methods A total of 30 children participated in the present study, divided into 3 groups: 10 children with microcephaly and prenatal exposure to the Zika virus; 10 normocephalic children with prenatal exposure to the Zika virus; and 10 children with no evidence of prenatal exposure to the virus. The FFR test was performed with the /da/ syllable. The LittlEars ® questionnaire was used with parents/guardians. Results For the FFR measurements, there was no difference between the groups. The children with exposure to the Zika virus presented a final score in the questionnaire below what is expected from children with normal hearing. A significant difference was observed for the final, semantic, and expressive scores between the group with microcephaly and the other groups. A strong negative correlation was seen between the LittlEars ® questionnaire final score and the FFR measurements for the group with microcephaly when compared with the other groups. Conclusion Children exposed to the Zika virus, with and without microcephaly, presented FFR patterns similar to what was seen in children with no evidence of virus exposure. However, they showed signs of immature auditory behavior, suggesting auditory development delay.

Cochlear Fibrocyte and Osteoblast Lineages Expressing Type 2 Deiodinase Identified with a Dio2CreERt2 Allele

Type 2 deiodinase (Dio2) amplifies levels of 3,5,3′-L-triiodothyronine (T3), the active form of thyroid hormone, and is essential for cochlear maturation and auditory development. However, cellular routes for endocrine signaling in the compartmentalized, anatomically complex cochlea are little understood. Dio2 generates T3 from thyroxine (T4), a more abundant thyroid hormone precursor in the circulation, and is dramatically induced in the cochlea before the onset of hearing. The evidence implies that specific Dio2-expressing cell types critically mediate T3 signaling but these cell types are poorly defined because Dio2 is expressed transiently at low levels. Here, using a Dio2CreERt2 knockin that activates a fluorescent reporter, we define Dio2-expressing cochlear cell types at high resolution in male or female mice. Dio2-positive cells were detected in vascularized supporting tissues but not in avascular internal epithelia, indicating segregation of T3-generating and T3-responding tissues. In the spiral ligament and spiral limbus, Dio2-positive fibrocytes clustered around vascular networks that convey T4 into cochlear tissues. In the otic capsule, Dio2-positive osteoblasts localized at cartilage surfaces as the bony labyrinth matures. We corroborated the identities of Dio2-positive lineages by RNA-sequencing of individual cells. The results suggest a previously unrecognized role for fibrocytes in mediating hormonal signaling. We discuss a model whereby fibrocytes mediate paracrine-like control of T3 signaling to the organ of Corti and epithelial target tissues.

A Survey of Neonatal Nurses Perspectives on Voice Use and Auditory Needs with Premature Infants in the NICU

Background: Exposure to the voice and language during the critical period of auditory development associated with the third trimester is thought to be an essential building block for language. Differences in the auditory experience associated with early life in the NICU may increase the risk of language delays for premature infants. NICU nurses are fundamental in the care of premature infants; how they use their voices may be important in understanding auditory experiences in the NICU. This study examined voice use behaviors of NICU nurses in the United States and their current knowledge of early auditory development. Method: An opt-in, online questionnaire. Results: Nurses reported using their voice more as the age of infants approached term gestation and speaking to infants was the most common type of voice use. Both infant and nurse factors influenced reported voice use decisions in the NICU. Nurses did not believe the NICU auditory environment to be sufficient to meet early auditory needs of premature infants but did believe that premature infants are exposed to adequate voice sounds. Conclusions: A gap in knowledge regarding the importance of early exposure to voice sounds may be a barrier to nurses using their voices to support early auditory development.

SOURCES OF SOUND LEVELS IN NICU AND INCUBATOR

Introduction: Currently there is limited research regarding estimated intrauterine sound levels. Benzaquen, Gagnon, Hunse& Foreman (1990) suggest however that intrauterine noise consists predominantly of low-frequency noise with sound levels being 40 dB above 500 Hz. Ideally, to promote healthy auditory development, sound levels in the NICU should be consistent with intrauterine environment. Each part has two sections A and B, the section A Methodology: is from more sick babies requiring Level 3 NICU care, whereas the section B is for babies requiring Level 2 NICU care. Our unit is 20 beded NICU with 15 beds level III and 5 beds level II unit, the study was conducted in level III unit. All sources of noise levels higher than 55 dBA in the NICU n Results: eed to be eliminated or mitigated. Since the alarms of equipments were important sources of noise in the NICU, eliminating or decreasing volume of alarms will reduce sound level. Every NICU requires a sound level assessment system in order to achieve environmental noise limiting guidelines and to get closer to the standard sound levels. Conclusion:By evaluating sound levels, the sources of noise can be identied and their effects on sound levels can be studied.

Characterization of developmental changes in spontaneous electrical activity of superior olivary neurons before hearing onset under injectable or volatile anesthesia

In this work we studied the impact of two widely used anesthetics on the electrical activity of auditory brainstem neurons during development. The spontaneous electrical activity in neonate rats of either sex was analyzed under the injectable mix of ketamine/xylazine (K/X mix) and the volatile anesthetic isoflurane (ISO). We used a ventral craniotomy in mechanically ventilated pups to carry out electrophysiology recordings in the superior olivary complex (SOC) between birth (postnatal day 0, P0) and P12. To characterize neuronal activity of single and ensembles of neurons, we performed patch clamp and multi-electrode experiments under different anesthetic conditions. Our results provide the first study that compares K/X mix and ISO in the same rodent species. We demonstrate that electrical activity of SOC neurons ramps up during development, and that the firing pattern of single units recorded in K/X mix was similar to that reported in ISO anesthetized rat pups. However, ISO displayed a large scatter on its suppressing effects on electrical activity when delivered at 1.5% in the presence or the absence of K/X mix. Taken together, our results shed light on the use of anesthetics for future studies to enable electrophysiology or optical imaging studies in-vivo to obtain functional information on the activity of medial olivochoclear neurons and their role in auditory development.

Cochlear Implantation in Infants: Why and How

In children with congenital deafness, cochlear implantation (CI) prior to 12 months of age offers the opportunity to foster more typical auditory development during late infancy and early childhood. Recent studies have found a positive association between early implantation and expressive and receptive language outcomes, with some children able to achieve normal language skills by the time of school entry. Universal newborn hearing screening improved early detection and diagnosis of congenital hearing loss, allowing for earlier intervention, including decision-making regarding cochlear implant (CI) candidacy. It can be more challenging to confirm CI candidacy in infants; therefore, a multidisciplinary approach, including objective audiometric testing, is recommended to not only confirm the diagnosis but also to counsel families regarding expectations and long-term management. Surgeons performing CI surgery in young children should consider both the anesthetic risks of surgery in infancy and the ways in which mastoid anatomy may differ between infants and older children or adults. Multiple studies have found CI surgery in infants can be performed safely and effectively. This article reviews current evidence regarding indications for implantation in children younger than 12 months of age and discusses perioperative considerations and surgical technique.

Functional Polymorphism of MMP9 and BDNF as Potential Biomarker of Auditory Neuroplasticity in Prelingual Deafness Treatment With Cochlear Implantation—A Retrospective Cohort Analysis

Genetic biomarkers of neuroplasticity in deaf children treated with cochlear implantation (CI) might facilitate their clinical management, especially giving them better chances of developing proficient spoken language. We investigated whether carrying certain variants of the genes encoding matrix metalloproteinase MMP9 and neurotrophin brain-derived neurotrophic factor ( BDNF), involved in synaptic plasticity, can be taken as prognostic markers of how well auditory skills might be acquired. Association analysis of functional MMP9 rs3918242 and BDNF rs6265 variants and the child’s auditory development measured at CI activation and 1, 5, 9, 14, and 24 months post CI activation with LittlEARS Questionnaire (LEAQ) was conducted in a group of 100 children diagnosed with DFNB1-related deafness, unilaterally implanted before the age of 2 years. Statistical analysis in the subgroup implanted after 1 year of life ( n = 53) showed significant association between MMP9 rs3918242 and LEAQ scores at 1 month ( p = .01), at 5 months ( p = .01), at 9 months ( p = .01), and at 24 months ( p = .01) after CI activation. No significant associations in the subgroup implanted before 1 year of life were observed. No significant associations between the BDNF rs6265 and LEAQ score were found. Multiple regression analysis ( R2 = .73) in the subgroup implanted after 1 year of life revealed that MMP9 rs3918242 was a significant predictor of treatment outcome. In conclusion, C/C rs3918242 MMP9 predisposes their deaf carriers to better CI outcomes, especially when implanted after the first birthday, than carriers of C/T rs3918242 MMP9.