Detection improvement for neonatal click evoked otoacoustic emissions by time-frequency filtering.

This study employed a time-frequency filtering technique to improve click evoked otoacoustic emission (CEOAE) detection at lower frequency bands, and hence to reduce the number of referral cases in neonatal OAE screening. Using this approach the detectability of CEOAEs, in terms of lower frequency SNRs and whole wave reproducibility, was significantly improved. Evaluations of screening outcomes demonstrated this method significantly reduced the overall referral rate, by 2.5 percentage points in initial CEOAE hearing screening. This approach may have potential application in OAE technology and in neonatal hearing screening programmes.

Preconditioning attenuates apoptosis and necrosis: role of protein kinase C epsilon and -delta isoforms.

Preconditioning reduces cardiomyocyte necrosis in vivo and in vitro, but it is unknown whether preconditioning blocks apoptosis. We wanted to compare the effects of preconditioning on necrosis and apoptosis in cardiomyocytes. Necrosis was detected with propidium iodide, and apoptosis was quantified by three complementary techniques: flow cytometry, TdT-mediated dUTP nick-end labeling assay, and DNA-laddering electrophoresis. Apoptosis increased with simulated ischemia time (6 h, 19 +/- 1%; 12 h, 27 +/- 2%; 18 h, 40 +/- 4%; 24 h, 54 +/- 4%; and 36 h, 83 +/- 4%; n = 6 for each group). Simulated ischemia and reoxygenation contributed equally to apoptosis (12-h ischemia, 27 +/- 2%, n = 6; 12-h ischemia and 12-h reoxygenation, 51 +/- 4%, n = 6; and 24-h ischemia, 54 +/- 5%, n = 8). Necrosis occurred primarily during reoxygenation; none was detected during simulated ischemia. Preconditioning with 10 min of simulated ischemia reduced necrosis (18 +/- 6%, n = 8) but had no effect on apoptosis. However, three 1-min cycles of simulated ischemia separated by 5 min of reoxygenation reduced necrosis and apoptosis similarly. The protein kinase C (PKC) inhibitors Go6976 (0.1 microM) or chelerythrene (4 microM) abolished the effect of preconditioning. Preconditioning selectively activated PKC epsilon but had no effect on PKC delta and on total PKC enzyme activity. Preconditioning protected against necrosis and apoptosis, but the preconditioning ischemia required for blocking apoptosis was less than that for reducing necrosis. Activation of PKC epsilon isoform is important in mediating the protection.

Paediatric hearing screening in the community: a comparison of outcomes from transient evoked and distortion product otoacoustic emission measures.

The present study aimed to compare TEOAE screening outcomes based on different pass/fail criteria and the outcomes from TEOAE and DPOAE measures in children. For the purpose of the study, the subjects were divided into two age groups: group 1 (n = 36; mean age 2.7 months, SD 1.2), and group 2 (n = 29; mean age 37.5 months, SD 16.3). Results indicated that the agreement of screening outcomes between pass/fail criteria for the TEOAE measure and between TEOAE and DPOAE measures was significantly lower for the younger group than for the older group. The greater variability in the younger age group could be partly attributed to the higher physiological noise produced by young infants. Irrespective of the pass/fail criteria used, the findings of the present study suggest that the OAE outcomes for children with weak OAEs or OAEs obscured by excessive noise were most variable.

Transient evoked otoacoustic emissions in 6-year-old school children: a normative study.

Great potential has recently been demonstrated for the application of transient evoked otoacoustic emissions (TEOAEs) in screening the hearing of school-aged children. The present study aimed to describe the range of TEOAE values obtained from a large cohort of 6-year-old children in school settings. Results indicated significant sex and ear asymmetry effects on signal-to-noise ratio, response, whole wave reproducibility, band reproducibility and noise levels. A prior history of ear infections was also shown to influence response level, whole wave reproducibility and band reproducibility. The sex, ear and history specific normative data tables derived may contribute to future improvements in the accuracy of hearing screening for 6-year-old school children.

Otoacoustic emission findings in Rett syndrome.

Rett syndrome is a neurologic disorder affecting mainly females after a seemingly normal 6 to 18 months of life. The resulting developmental disabilities include apparent dementia and loss of acquired language, social skills, and purposeful hand use. The present investigation assessed 10 individuals with Rett syndrome and a control group matched for age and sex. The present study aimed to determine the clinical feasibility of obtaining otoacoustic emissions (OAEs) from the Rett syndrome group and to compare the characteristics of the transient evoked and distortion-product OAEs obtained from the two subject groups. Results indicated that OAE evaluation is a clinically feasible method of assessing individuals with Rett syndrome. The Rett syndrome group had less robust OAEs, especially in the higher frequencies, when compared to the control group. Seven of the Rett syndrome group were identified as having reduced or absent OAEs in at least one ear. These findings suggest a need for hearing screening at an early age and monitoring of hearing on a regular basis.

Infant hearing screening: a comparison of two techniques.

Hearing screening programs for Australian children are known to have poor coverage in many areas. In addition, only a minority of children are screened for hearing loss before 2 years of age. However, early detection of hearing loss and early treatment are generally considered very important to successful rehabilitation outcomes. Traditional methods of screening infants have limitations with their accuracy in detecting children with hearing loss. This study compared the results obtained with a traditional questionnaire approach to screening and a newer objective technique involving otoacoustic emission measures. Poor correlation was found between pass rates for the two techniques, suggesting that the questionnaire approach is not an accurate screening method for detecting infant hearing loss. With further development, otoacoustic emission testing holds promise as an objective alternative hearing screening procedure.