Is cochlear synapse loss an origin of low-frequency hearing loss associated with endolymphatic hydrops?

Carla V. Valenzuela; Choongheon Lee; Abby Mispagel; Atri Bhattacharyya; Shannon M. Lefler; Shelby Payne; Shawn S. Goodman; Amanda J. Ortmann; Craig A. Buchman; Mark A. Rutherford; Jeffery T. Lichtenhan

doi:10.1016/j.heares.2020.108099

Is cochlear synapse loss an origin of low-frequency hearing loss associated with endolymphatic hydrops?

Carla V. Valenzuela, Choongheon Lee, Abby Mispagel, Atri Bhattacharyya, Shannon M. Lefler, Shelby Payne, Shawn S. Goodman, Amanda J. Ortmann, Craig A. Buchman, Mark A. Rutherford, Jeffery T. Lichtenhan

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6 Scopus citations

Abstract

There is a strong association between endolymphatic hydrops and low-frequency hearing loss, but the origin of the hearing loss remains unknown. A reduction in the number of cochlear afferent synapses between inner hair cells and auditory nerve fibres may be the origin of the low-frequency hearing loss, but this hypothesis has not been directly tested in humans or animals. In humans, measurements of hearing loss and postmortem temporal-bone based measurements of endolymphatic hydrops are generally separated by large amounts of time. In animals, there has not been a good objective, physiologic, and minimally invasive measurement of low-frequency hearing. We overcame this obstacle with the combined use of a reliable surgical approach to ablate the endolymphatic sac in guinea pigs and create endolymphatic hydrops, the Auditory Nerve Overlapped Waveform to measure low-frequency hearing loss (≤ 1 kHz), and immunohistofluorescence-based confocal microscopy to count cochlear synapses. Results showed low- and mid-(1–4 kHz) frequency hearing loss at all postoperative days, 1, 4, and 30. There was no statistically significant loss of cochlear synapses, and there was no correlation between synapse loss and hearing function. We conclude that cochlear afferent synaptic loss is not the origin of the low-frequency hearing loss in the early days following endolymphatic sac ablation. Understanding what is, and is not, the origin of a hearing loss can help guide preventative and therapeutic development.

Original language	English
Article number	108099
Journal	Hearing research
Volume	398
DOIs	https://doi.org/10.1016/j.heares.2020.108099
State	Published - Dec 2020

Keywords

Auditory Nerve Overlapped Waveform
Endolymphatic hydrops
Low-frequency hearing loss
Ménière's disease
Ribbon synapse

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10.1016/j.heares.2020.108099

Cite this

@article{8bd8da6369f94bc39a3344198bbb99de,

title = "Is cochlear synapse loss an origin of low-frequency hearing loss associated with endolymphatic hydrops?",

abstract = "There is a strong association between endolymphatic hydrops and low-frequency hearing loss, but the origin of the hearing loss remains unknown. A reduction in the number of cochlear afferent synapses between inner hair cells and auditory nerve fibres may be the origin of the low-frequency hearing loss, but this hypothesis has not been directly tested in humans or animals. In humans, measurements of hearing loss and postmortem temporal-bone based measurements of endolymphatic hydrops are generally separated by large amounts of time. In animals, there has not been a good objective, physiologic, and minimally invasive measurement of low-frequency hearing. We overcame this obstacle with the combined use of a reliable surgical approach to ablate the endolymphatic sac in guinea pigs and create endolymphatic hydrops, the Auditory Nerve Overlapped Waveform to measure low-frequency hearing loss (≤ 1 kHz), and immunohistofluorescence-based confocal microscopy to count cochlear synapses. Results showed low- and mid-(1–4 kHz) frequency hearing loss at all postoperative days, 1, 4, and 30. There was no statistically significant loss of cochlear synapses, and there was no correlation between synapse loss and hearing function. We conclude that cochlear afferent synaptic loss is not the origin of the low-frequency hearing loss in the early days following endolymphatic sac ablation. Understanding what is, and is not, the origin of a hearing loss can help guide preventative and therapeutic development.",

keywords = "Auditory Nerve Overlapped Waveform, Endolymphatic hydrops, Low-frequency hearing loss, M{\'e}ni{\`e}re's disease, Ribbon synapse",

author = "Valenzuela, {Carla V.} and Choongheon Lee and Abby Mispagel and Atri Bhattacharyya and Lefler, {Shannon M.} and Shelby Payne and Goodman, {Shawn S.} and Ortmann, {Amanda J.} and Buchman, {Craig A.} and Rutherford, {Mark A.} and Lichtenhan, {Jeffery T.}",

note = "Funding Information: We thank Dr. Dorina Kallogjeri for assistance with the statistical analysis, and Dr. John J. Guinan, Jr. for critiquing an earlier version of this manuscript. We thank two reviewers for their helpful comments. This research was supported by the American Academy of Otolaryngology- Head and Neck Surgery Foundation Centralized Otolaryngology Research Efforts, through the AAO-HNSF Resident Research Award (C.V.V.), the National Institute of Deafness and Other Communication Disorders within the National Institutes of Health, through R01 DC014997 (J.T.L.), R01 DC014712 (M.A.R.), and the “Development of Clinician/Researchers in Academic ENT” training grant T32 DC000022 (C.V.V.). Publisher Copyright: {\textcopyright} 2020",

year = "2020",

month = dec,

doi = "10.1016/j.heares.2020.108099",

language = "English",

volume = "398",