Responsiveness of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency

Shuman He, Bahar S. Shahsavarani, Tyler C. McFayden, Haibo Wang, Katherine E. Gill, Lei Xu, Xiuhua Chao, Jianfen Luo, Ruijie Wang, Nancy He

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Objectives: This study aimed to (1) investigate the responsiveness of the cochlear nerve (CN) to a single biphasic-electrical pulse in implanted children with cochlear nerve deficiency (CND) and (2) compare their results with those measured in implanted children with normal-size CNs. Design: Participants included 23 children with CND (CND1 to CND23) and 18 children with normal-size CNs (S1 to S18). All subjects except for CND1 used Cochlear Nucleus cochlear implants with contour electrode arrays in their test ears. CND1 was implanted with a Cochlear Nucleus Freedom cochlear implant with a straight electrode array in the test ear. For each subject, the CN input/output (I/O) function and the refractory recovery function were measured using electrophysiological measures of the electrically evoked compound action potential (eCAP) at multiple electrode sites across the electrode array. Dependent variables included eCAP threshold, the maximum eCAP amplitude, slope of the I/O function, and time-constants of the refractory recovery function. Slopes of I/O functions were estimated using statistical modeling with a sigmoidal function. Recovery time-constants, including measures of the absolute refractory period and the relative refractory period, were estimated using statistical modeling with an exponential decay function. Generalized linear mixed-effect models were used to evaluate the effects of electrode site on the dependent variables measured in children with CND and to compare results of these dependent variables between subject groups. Results: The eCAP was recorded at all test electrodes in children with normal-size CNs. In contrast, the eCAP could not be recorded at any electrode site in 4 children with CND. For all other children with CND, the percentage of electrodes with measurable eCAPs decreased as the stimulating site moved in a basal-to-apical direction. For children with CND, the stimulating site had a significant effect on the slope of the I/O functions and the relative refractory period but showed no significant effect on eCAP threshold and the maximum eCAP amplitude. Children with CND had significantly higher eCAP thresholds, smaller maximum eCAP amplitudes, flatter slopes of I/O functions, and longer absolute refractory periods than children with normal-size CNs. There was no significant difference in the relative refractory period measured in these two subject groups. Conclusions: In children with CND, the functional status of the CN varied along the length of the cochlea. Compared with children with normalsize CNs, children with CND showed reduced CN responsiveness to electrical stimuli. The prolonged CN absolute refractory period in children with CND might account for, at least partially, the observed benefit of using relatively slow pulse rate in these patients.

Original languageEnglish (US)
Pages (from-to)238-250
Number of pages13
JournalEar and hearing
Volume39
Issue number2
DOIs
StatePublished - Jan 1 2018

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Cochlear Nerve
Action Potentials
Electrodes
Cochlear Nucleus
Cochlear Implants
Recovery of Function
Ear
Cochlea

Keywords

  • Cochlear implant
  • Cochlear nerve
  • Cochlear nerve deficiency
  • Electrically evoked auditory compound action potentials
  • Neural refractoriness

ASJC Scopus subject areas

  • Otorhinolaryngology
  • Speech and Hearing

Cite this

He, S., Shahsavarani, B. S., McFayden, T. C., Wang, H., Gill, K. E., Xu, L., ... He, N. (2018). Responsiveness of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency. Ear and hearing, 39(2), 238-250. https://doi.org/10.1097/AUD.0000000000000467

Responsiveness of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency. / He, Shuman; Shahsavarani, Bahar S.; McFayden, Tyler C.; Wang, Haibo; Gill, Katherine E.; Xu, Lei; Chao, Xiuhua; Luo, Jianfen; Wang, Ruijie; He, Nancy.

In: Ear and hearing, Vol. 39, No. 2, 01.01.2018, p. 238-250.

Research output: Contribution to journalArticle

He, S, Shahsavarani, BS, McFayden, TC, Wang, H, Gill, KE, Xu, L, Chao, X, Luo, J, Wang, R & He, N 2018, 'Responsiveness of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency', Ear and hearing, vol. 39, no. 2, pp. 238-250. https://doi.org/10.1097/AUD.0000000000000467
He, Shuman ; Shahsavarani, Bahar S. ; McFayden, Tyler C. ; Wang, Haibo ; Gill, Katherine E. ; Xu, Lei ; Chao, Xiuhua ; Luo, Jianfen ; Wang, Ruijie ; He, Nancy. / Responsiveness of the electrically stimulated cochlear nerve in children with cochlear nerve deficiency. In: Ear and hearing. 2018 ; Vol. 39, No. 2. pp. 238-250.
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author = "Shuman He and Shahsavarani, {Bahar S.} and McFayden, {Tyler C.} and Haibo Wang and Gill, {Katherine E.} and Lei Xu and Xiuhua Chao and Jianfen Luo and Ruijie Wang and Nancy He",
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AU - He, Shuman

AU - Shahsavarani, Bahar S.

AU - McFayden, Tyler C.

AU - Wang, Haibo

AU - Gill, Katherine E.

AU - Xu, Lei

AU - Chao, Xiuhua

AU - Luo, Jianfen

AU - Wang, Ruijie

AU - He, Nancy

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N2 - Objectives: This study aimed to (1) investigate the responsiveness of the cochlear nerve (CN) to a single biphasic-electrical pulse in implanted children with cochlear nerve deficiency (CND) and (2) compare their results with those measured in implanted children with normal-size CNs. Design: Participants included 23 children with CND (CND1 to CND23) and 18 children with normal-size CNs (S1 to S18). All subjects except for CND1 used Cochlear Nucleus cochlear implants with contour electrode arrays in their test ears. CND1 was implanted with a Cochlear Nucleus Freedom cochlear implant with a straight electrode array in the test ear. For each subject, the CN input/output (I/O) function and the refractory recovery function were measured using electrophysiological measures of the electrically evoked compound action potential (eCAP) at multiple electrode sites across the electrode array. Dependent variables included eCAP threshold, the maximum eCAP amplitude, slope of the I/O function, and time-constants of the refractory recovery function. Slopes of I/O functions were estimated using statistical modeling with a sigmoidal function. Recovery time-constants, including measures of the absolute refractory period and the relative refractory period, were estimated using statistical modeling with an exponential decay function. Generalized linear mixed-effect models were used to evaluate the effects of electrode site on the dependent variables measured in children with CND and to compare results of these dependent variables between subject groups. Results: The eCAP was recorded at all test electrodes in children with normal-size CNs. In contrast, the eCAP could not be recorded at any electrode site in 4 children with CND. For all other children with CND, the percentage of electrodes with measurable eCAPs decreased as the stimulating site moved in a basal-to-apical direction. For children with CND, the stimulating site had a significant effect on the slope of the I/O functions and the relative refractory period but showed no significant effect on eCAP threshold and the maximum eCAP amplitude. Children with CND had significantly higher eCAP thresholds, smaller maximum eCAP amplitudes, flatter slopes of I/O functions, and longer absolute refractory periods than children with normal-size CNs. There was no significant difference in the relative refractory period measured in these two subject groups. Conclusions: In children with CND, the functional status of the CN varied along the length of the cochlea. Compared with children with normalsize CNs, children with CND showed reduced CN responsiveness to electrical stimuli. The prolonged CN absolute refractory period in children with CND might account for, at least partially, the observed benefit of using relatively slow pulse rate in these patients.

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KW - Cochlear implant

KW - Cochlear nerve

KW - Cochlear nerve deficiency

KW - Electrically evoked auditory compound action potentials

KW - Neural refractoriness

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