| Summary: | 碩士 === 國立台北護理學院 === 聽語障礙科學研究所 === 96 === Background: This study is designed for comparing the cochlear traveling time difference between ears of Meniere’s disease (MD) patients and normal subjects. Both derived-band auditory brainstem responses (ABRs) and compound action potentials (CAPs) detecting techniques were used. To improve the recognized waveform latencies, the CAP was detected by using the Biologic TM-EcochGtrode system electrodes. Derived-band technique was adopted and modified from previous literature by applying an ipsilateral high-pass masking noise.
Material and Methods: This study received institutional review board approval. Twenty-two unilateral Meniere’s disease patients (8 males, 14 females) diagnosed according to the 1995 guidelines published by American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS, 1995) were included with the symptom presented within one week, aged 26 to 60 years, and thirty ears from thirty subjects with hearing sensitivity within normal limits (15 left, 15 right), aged 20 to 43 years. All subjects underwent extratympanic electrode insertion using the Biologic TM-ECochGtrode system (Biologic Systems Corp, Mundelein,Ill) and ABR responses to six stimulus conditions were obtained, including click alone and click presented with various ipsilateral pink noise high-pass filtered maskers (cut-off frequencies were close to 8000, 4000, 2000, 1000 and 500 Hz). Six auditory brainstem evoked potentials are recorded and subtracted by each other, resulting in above 8000 Hz, 8000-4000 Hz, 4000-2000 Hz, 2000-1000 Hz and 1000-500 Hz five derived-band ABRs. Estimates from derived-band ABRs and CAP were comparable to each other.
Results: More than 85 % for both derived-band CAP and wave V latencies can be identified in a low-frequency band (500-1000 Hz). The percentage of recognizable latency presented in derived-band CAP (93.4 %) is higher than the one in ABR wave V (89.0 %) across all frequencies. Both peak latencies presented in derived-band CAP and ABR wave V increase as the cochlea is masked from 8 kHz and higher down to 0.5 kHz. The absolute band-derived latency distribution presented in MD group overlaps the one in normal hearing group either observed in CAP or wave V. The latency difference between click alone and band-derived ABR detected both in CAP and wave V, also revealed no significant difference compared between experimental and normal groups. However, the latency change between click alone and band-derived ABR evaluated in both CAP and wave V, significant increase in MD group when compared with normal hearing group at low frequency band (500-1000 Hz) (P< 0.05).
Conclusion:
1. Recognizable latencies presented in derived-band CAP are improved by tympanic membrane electrodes recording.
2. With this modified derived-band CAP recording, the identification ratio of cochlear traveling wave velocity in CAP is higher than the one in ABR wave V.
3. By comparing the absolute peak latency values at each band-derived frequency between MD group and control group, there is no significant difference. This result may be referred to the variation of disease progression in collected MD patients in this study.
4. Both band-derived CAP and ABR wave V can detect the alteration of the cochlear traveling wave velocity in a low frequency band of 500-1000 Hz when compared using latency change in MD group. This result suggests that the derived-band technique may be more sensitive in detecting an endolymphatic hydrop condition in an assumed low frequency map in the cochlea.
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