Case Control Study
Copyright ©The Author(s) 2025. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. Oct 6, 2025; 13(28): 108180
Published online Oct 6, 2025. doi: 10.12998/wjcc.v13.i28.108180
Medial olivocochlear reflex dysfunction in multiple sclerosis: The influence of brainstem lesion localization and its clinical implications
Ibrahim Salih Gecer, Alper Tabaru, Beyhan Yilmaz, Elif Kaya, Nurhan Kaya Tutar, Bekircan Gumuslu, Mehmet Faruk Oktay
Ibrahim Salih Gecer, Department of Otorhinolaryngology, Istanbul Bakirkoy Research and Training Hospital, Istanbul 34147, Türkiye
Alper Tabaru, Department of Otorhinolaryngology, Van Research and Training Hospital, Van 65170, Türkiye
Beyhan Yilmaz, Bekircan Gumuslu, Mehmet Faruk Oktay, Department of Otorhinolaryngology, Istanbul Bagcilar Research and Training Hospital, Istanbul 34200, Türkiye
Elif Kaya, Department of Audiology, Istanbul Bagcilar Research and Training Hospital, Istanbul 34200, Türkiye
Nurhan Kaya Tutar, Department of Neurology, Istanbul Bagcilar Research and Training Hospital, Istanbul 34200, Türkiye
Author contributions: Gecer IS and Yilmaz B conceived the ideas and experimental design of the study; Tutar NK, Kaya, and Gumuslu B performed the data collection; Oktay MF and Tabaru A performed the data analyses and interpretation; Tabaru A provided revisions to the scientific content of the manuscript; Tabaru A and Yilmaz B provided grammatical revisions to the manuscript; Oktay MF provided access to crucial research components; Yilmaz B was the advisor for the project.
Institutional review board statement: This study was reviewed and approved by the Institutional Review Board (IRB) of İstanbul Training and Research Hospital (Approval No. 2781, dated March 19, 2021). All procedures were conducted in accordance with the ethical standards of the institutional and national research committee, and with the 1964 Helsinki Declaration and its later amendments.
Informed consent statement: All participants were informed about the purpose, procedures, risks, and benefits of the study prior to participation. Written informed consent was obtained from all individuals included in the study. Participation was voluntary, and participants were allowed to withdraw from the study at any time without any consequences. Confidentiality of all personal data was maintained throughout the research process.
Conflict-of-interest statement: The authors have no conflicts of interest to declare.
STROBE statement: The authors have read the STROBE Statement – checklist of items, and the manuscript was prepared and revised according to the STROBE Statement – checklist of items.
Data sharing statement: The datasets generated and analyzed during the current study are available from the corresponding author upon reasonable request. All data have been de-identified to ensure participant confidentiality and comply with ethical standards. Researchers requesting access will be required to outline the purpose of their use and agree to data use terms. Where applicable, supporting documentation and code used in the analysis can also be made available to facilitate reproducibility of the findings.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Ibrahim Salih Gecer, Department of Otorhinolaryngology, Istanbul Bakirkoy Research and Training Hospital, Dr. Tevfik Saglam Cad No: 11 Zuhuratbaba Mah Bakirkoy, Istanbul 34147, Türkiye. gecersalih@gmail.com
Received: April 9, 2025
Revised: May 26, 2025
Accepted: July 16, 2025
Published online: October 6, 2025
Processing time: 122 Days and 9.2 Hours
Abstract
BACKGROUND

Multiple sclerosis (MS) is known to affect many sensory systems, yet most auditory research in MS has focused on the afferent pathways, with relatively few studies examining efferent function. The brainstem is a common site for MS plaques, and the medial olivocochlear (MOC) system is located in the superior olivary complex (SOC) of the brainstem. The cochlear nuclei are also involved in the MOC reflex arc. Additionally, the temporal cortex can modulate the SOC and cochlear nucleus, so lesions in the brainstem or temporal cortex may affect the MOC reflex in MS.

AIM

To investigate efferent auditory system activity in patients with multiple sclerosis via the MOC reflex.

METHODS

The study included 50 patients with MS and 50 healthy controls. Patients with MS were divided into three subgroups according to cranial magnetic resonance imaging findings: Patients with brainstem lesions (Group 1, n = 20); patients with temporal cortex lesions without brainstem involvement (Group 2, n = 20); and patients without any lesions in the brainstem or temporal cortex (Group 3, n = 10). Tympanometry, acoustic stapedial reflex thresholds, pure-tone audiometry, and transient-evoked otoacoustic emission (TEOAE) tests (with and without contralateral noise) were performed for all participants.

RESULTS

There was no significant difference in pure-tone hearing thresholds or baseline TEOAE amplitudes between the MS and control groups, indicating normal cochlear function in patients with MS; however, MOC reflex suppression was significantly reduced in patients with MS compared to controls (P = 0.021). In particular, Group 1 (MS with brainstem lesions) showed the lowest mean suppression values, which was significantly lower than that of Group 2 and the control group (P = 0.002). By contrast, Group 2 and Group 3 did not significantly differ from controls. Additionally, patients with MS exhibited a sex difference in MOC function: Male patients had significantly lower suppression compared to female patients both within Group 1 and in the MS group as a whole.

CONCLUSION

The findings indicate that the efferent auditory system (specifically the MOC reflex) is affected by MS. MOC reflex activity was most significantly decreased in patients with MS with brainstem lesions, while temporal cortex lesions alone did not appear to notably impair the MOC reflex. Diminished MOC activity may underlie various auditory difficulties in patients with MS (e.g., hearing in noise), and loss of efferent suppression could contribute to symptoms such as hyperacusis or tinnitus in this population. Further studies are needed to better understand the relationship between MOC dysfunction and auditory symptoms in MS, as well as the potential diagnostic value of MOC testing in MS.

Keywords: Multiple sclerosis; Inner ear; Hearing loss; Medial olivocochlear reflex; Autoimmune disease

Core Tip: This study provides evidence that the efferent auditory pathway, assessed via the medial olivocochlear (MOC) reflex, is compromised in patients with multiple sclerosis (MS), particularly in those with brainstem lesions. The findings suggest that demyelinating lesions in the brainstem, where the MOC system is anatomically localized, may impair auditory modulation. Temporal cortex involvement appears to have no significant effect. These results support the relevance of efferent auditory evaluation in understanding auditory dysfunctions associated with MS.