Usefulness of masseter vestibular evoked myogenic potentials in identifying brainstem dysfunction among individuals with multiple sclerosis.

OBJECTIVE: The present study aimed to investigate the findings of cervical, ocular and masseter vestibular evoked myogenic potentials (cVEMP, oVEMP and mVEMP) among Multiple sclerosis (MS) and correlate with clinical and MRI findings. DESIGN: Standard group comparison research design. STUDY SAMPLE: Individuals with relapsing-remitting MS (n = 45) and age-sex-matched controls (n = 45) were the participants. All of them underwent case history, neurological examination, cVEMP, oVEMP and mVEMP testing. MRI was obtained only for MS participants. RESULTS: Abnormal result on at least one vestibular evoked myogenic potential (VEMP) sub-type was evidenced in 95.56% of participants whereas, unilateral or bilateral abnormal result on all three VEMP sub-types was observed in 60% of participants. The mVEMP abnormality was higher (82.22%) than cVEMP (75.56%) and oVEMP (75.56%) abnormalities but the differences were not significant (p > 0.05). There was no significant association of VEMP abnormalities with the presence of the brainstem symptoms, the brainstem signs, or the MRI lesions (p > 0.05). In the MS group, 38% had normal brainstem MRI; however, mVEMP, cVEMP and oVEMP abnormalities were evidenced in 82.4%, 64.7% and 52.94%, respectively. CONCLUSIONS: Among the three VEMP sub-types, mVEMP appears to be of greater value in identifying silent brainstem dysfunction undetected by clinical and MRI findings in the MS population.

Analysis of SLC26A4 Gene in Individuals with Non Syndromic Hearing Impairment in Relation with GJB2 Associated Mutations.

Background: Hearing Loss (HL) is the most common sensory disorder. HL commonly ranges from mild to severe. Persons with HL face difficulty in hearing conversations or sounds through one ear or both ears, which impacts one's ability to interact with others. Hence it is a communicable disorder that makes people socially isolated, lonely, and frustrated. HL in children severely affects language development. The people who are referred to as 'Deaf' with very little or no hearing capabilities, are considered as having profound hearing loss. More than 124 genes are causative for Non-Syndromic HL (NSHL) with varying inheritance, among which the SLC26A4 mutations are the second commonest cause of hereditary HL across the globe. Methods: Samples from 70 NSHL patients were analyzed through Next-Generation Sequencing (NGS) and generated five pathogenic variants [N246fs (rs918684449), K564fs (rs746427774), F122fs, V239D (rs111033256), T721M (rs121908363)] each with frequency of 1.42%. Three missense variants [S399P (rs747431002), L597S (rs55638457), and G6V (rs111033423)] were reported under the "uncertain" category. All the collected samples were further genotyped to look for the possibility of having GJB2 and HL-associated mutations. Results: Out of five SLC26A4 pathogenic mutations N246fs (rs918684449) and K564fs (rs746427774) were observed in samples which were positive for GJB2-HL associated candidate mutations [W24X (rs104894396), Q124X (rs397516874) and W77X (rs80338944)]. Similarly, pathogenic variants F122fs, V239D (rs111033256) and T721M (rs121908363) were observed in patient samples which were negative for GJB2-HL associated mutations. Conclusion: Our data will expand the list of variants underlying NSHL and encourage further genotype SLC26A4 gene concerning the south Indian population with a large sample size.

Tone Burst Masseter Vestibular Evoked Myogenic Potentials: Normative Values and Test-Retest Reliability.

BACKGROUND: Masseter vestibular evoked myogenic potential (mVEMP) is a recent tool for the assessment of vestibular and trigeminal pathways. Though a few studies have recorded mVEMP using click stimuli, there are no reports of these potentials using the more conventional VEMP eliciting stimuli, the tone bursts. PURPOSE: The aim of the study is to establish normative values and determine the test-retest reliability of tone burst evoked mVEMP. RESEARCH DESIGN: The research design type is normative study design. STUDY SAMPLE: Forty-four healthy participants without hearing and vestibular deficits in the age range of 18 to 50 years participated in the study. DATA COLLECTION AND ANALYSIS: All participants underwent mVEMP testing using 500 Hz tone-burst stimuli at 125 dB peSPL. Ten participants underwent second mVEMP testing within 1 month of the initial testing to estimate the test-retest reliability. RESULTS: Tone burst mVEMP showed robust responses in all participants. There were no significant ear and sex differences on any mVEMP parameter (p > 0.05); however, males had significantly higher EMG normalized peak-to-peak amplitude than females. Intraclass correlation coefficient (ICC) values of tone burst mVEMP showed excellent test-retest reliability (ICC >0.75) for ipsilateral and contralateral p11 latency, ipsilateral EMG normalized p11-n21 peak to peak amplitude, and amplitude asymmetry ratio. Fair and good test-retest reliability (0.4 < ICC > 0.75) was observed for ipsilateral and contralateral n21 latency, contralateral EMG normalized peak-to-peak amplitude, and amplitude asymmetry ratio. CONCLUSION: Tone burst mVEMP is a robust and reliable test for evaluating the functional integrity of the vestibulomasseteric reflex pathway.