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V Amplitude (v + amplitude)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

Click and Low-, Middle-, and High-Frequency Toneburst Stimulation of the Canine Cochlea

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 3 2002
G. Ter Haar
A method was developed to deliver tonebursts ranging in frequency from 1 to 32 kHz for frequency-specific assessment of the canine cochlea. Brainstem auditory-evoked responses (early latency responses, 0,10 ms) to a click (CS) and to 1-, 2-, 4-, 8-, 12-, 16-, 24-, and 32-kHz toneburst stimulations (TS) were compared at 80-dB sound pressure level stimulus (SPL) intensity in 10 adult dogs. All stimulations yielded a 5,7 positive wave pattern, with the exception of the 1-kHz TS, which evoked a frequency-following response (FFR). Thresholds were lowest for the CS and the 12- and 16-kHz TS. All individual peak latencies for TS were significantly (P, .05) longer than for CS. Peak I latencies were significantly (P,.05) shorter for the 12- and 16-kHz TS than for the other TS. Interpeak latencies I-V were significantly (P, .05) longer for the 4- to 32-kHz TS than for CS. Differences in interpeak latencies I,III were not significant. Amplitudes of waves I and V were significantly (P, .05) lower for TS than for CS, except for higher wave V amplitude (P, .05) at 2- and 32-kHz TS. Peak I-V amplitude ratios were significantly (P, .05) higher for the 2-, 4-, 16-, 24-, and 32-kHz TS and lower for the 8- and 12-kHz TS, compared to CS. We conclude that reproducible information on frequency specificity of the canine cochlea can be obtained by TS. This report provides a normative database for parameters needed to evaluate frequency-specific hearing loss in dogs. [source]

Electrophysiologic Effects of Placing Cochlear Implant Electrodes in a Perimodiolar Position in Young Children,

THE LARYNGOSCOPE, Issue 1 2004
Phillip A. Wackym MD
Abstract Objective The purpose of this study was to intraoperatively record the electrically evoked auditory brainstem response (EABR) before and after placement of the electrode positioning system (EPS) (CII Bionic Ear with HiFocus I cochlear implant electrode array) as well as before and after stylet removal (Nucleus Contour cochlear implant electrode array). It was hypothesized that physiologic changes would occur after perimodiolar positioning of the electrode array and these changes would be evident from the EABR recordings. Study Design Consecutive young (11,36 month old) pediatric cochlear implant recipients (n = 17) had intraoperative EABRs recorded from three intracochlear electrodes that represented apical, medial, and basal locations. Wave V amplitudes and thresholds were studied relative to electrode location and pre- versus postperimodiolar positioning. These evoked potential measures were analyzed for statistical significance. Setting Tertiary referral children's hospital/medical college. Results Wave V thresholds of the EABR were lower, and amplitudes were larger after perimodiolar positioning, although the changes were dependent on electrode location and implant design. Statistically significant decreases in EABR wave V threshold and increases in suprathreshold wave V amplitude were found for the basal electrode for the CII Bionic Ear HiFocus I and for the apical electrode for the Nucleus Contour. Conclusions Placement of either the CII Bionic Ear HiFocus I or Nucleus Contour cochlear implant electrode array in the perimodiolar position in young children resulted in less electrical current necessary to stimulate the auditory system. Changes in electrophysiologic thresholds and amplitudes, measured with EABR, indicate that the electrode array is placed closer to the modiolus with both electrode designs. [source]

Comparison of brainstem auditory evoked responses recorded at different presentation rates of clicks in term neonates after asphyxia

ACTA PAEDIATRICA, Issue 12 2001
ZD Jiang
This study examined whether high presentation rates of clicks while recording brainstem auditory evoked responses (BAER) can improve the detection of central auditory impairment in asphyxiated neonates using the BAER. The BAER was analysed at different presentation rates of clicks within the first week after birth in 38 term neonates who suffered perinatal asphyxia. At the routinely used 21 s,1 clicks all BAER wave latencies increased significantly (ANOVA, p < 0.05-0.01). After excluding five neonates who had a significantly elevated BAER threshold, only wave V latency increased slightly (p < 0.05). The interpeak intervals of I,V and III,V also increased slightly (both p < 0.05). Similar results were found at 51 s,1 clicks. As the clicks were increased to 91 s,1, the III,V interval increased more significantly (p < 0.01) and the III,V/I,III interval ratio also increased significantly (p < 0.01). In particular, wave V amplitude reduced more significantly than that in normal term controls (p < 0.01). Compared with values in the controls, wave V amplitude reduced by 4.5%, 12.2% and 24.7% at 21, 51 and 91 s,1 clicks, respectively. Conclusion: Although a moderate increase in the rate (e.g. 51 s,1) while recording the BAER did not improve the detection of hypoxic-ischaemic auditory impairment, a significant increase (e.g. 91 s,1) did, which mainly indicates an abnormal reduction in wave V amplitude. [source]