Sujeet Kumar Sinha

Involvement of peripheral vestibular nerve in individuals with auditory neuropathy

The vestibulocochlear nerve is a sensory nerve that serves the organs of hearing and equilibrium. Neuropathies of the nerve, particularly auditory neuropathy may be caused by primary demyelination or by axonal diseases. In disorders affecting the cochlear nerve, it is probable that the vestibular nerve is involved as well. There are isolated reports of the involvement of the inferior vestibular nerve (using vestibular-evoked myogenic potentials) in individuals with AN. However, there is a dearth of information on the involvement of the superior vestibular nerve and other functions such as optokinetic, saccade and vestibulo-occular reflex. A total of three subjects diagnosed as having auditory neuropathy, underwent an extensive vestibular assessment consisting of clinical tests of stability (Romberg, Fukuda stepping test), administration of dizziness questionnaire developed by Maryland hearing and balance centre, cervical vestibular-evoked myogenic potentials and a standard electronystagmography test battery. In the present study, the entire subject population assessed showed hypofunctional caloric responses and absent VEMPs. Two out of the three subjects were asymptomatic of vestibular dysfunction. On the clinical tests of stability, two subjects showed deviations to the right, while one subject performed normally. Thus, the present study indicates a possible involvement of peripheral vestibular nerve involvement in individuals with auditory neuropathy.

Vestibular Evoked Myogenic Potential as a Tool to Identify Vestibular Involvement in Auditory Neuropathy

Abstract Auditory neuropathy is characterized by a unique pattern of hearing loss, absent or severely distorted ABR, preserved OAE, and measurable cochlear microphonics. As the vestibular and cochlear branches are parts of the same fiber bundle system called the vestibulocochlear nerve, it is likely that neuropathy in one (cochlear branch) might also form a feature in the other (vestibular branch). But none of these tests are able to explain the involvement of the vestibular system in these cases. Thus, the present study was undertaken to explore this aspect to determine: (1) the involvement of the vestibular pathway in cases with auditory neuropathy; (2) if there is any relationship between vestibular abnormalities and the symptoms they mimic; and (3) the incidence of vestibular abnormality in patients with auditory neuropathy. Ten subjects (7 male and 3 female) in the age range of 15 to 35 years participated in this study. The test battery administered included pure-tone audiometry, ABR, OAE, Immittance, and VEMP. The results showed: (1) nine out of the 10 subjects showed abnormal or absent VEMP; (2) there is no one-to-one correlation between the abnormal or absent VEMP and the vestibular symptoms that these subjects present; and (3) 80% of the ears with auditory neuropathy showed abnormal VEMP results giving an indication of high incidence of vestibular involvement in the auditory neuropathy population. The present study provides evidence for involvement of the vestibular branch of the VIIIth cranial nerve in a high percentage of the auditory neuropathy population; hence, it is suggested that there is need for vestibular assessment in cases of auditory neuropathy that would help to better understand the disorder. It is also suggested that the term “acoustic neuropathy” be used to indicate those patients in whom only the acoustic nerve is affected and “vestibuloacoustic neuropathy” to label those patients who also show involvement of the vestibular system.

Auditory Neuropathy/Dys-synchrony In School-aged Hearing-impaired Children: A South Indian Perspective

Abstract Recently, use of otoacoustic emission technology has led to identification of auditory neuropathy as a distinct hearing disorder in children as well as adults. Children with auditory neuropathy require audiologic and educational management that may differ from that required by other hearing impaired. The purpose of this study was to estimate the prevalence and audiologic characteristics of auditory dys-synchrony in school-aged hearing- impaired children in an integrated school; 220 students from grade one to grade eight were recruited for the study. Initially all the subjects were screened using DPOAE and the subjects who had otoacoustic emissions present were subjected for a detailed diagnostic evaluation. Results showed that the prevalence of auditory dys-synchrony was around 2.27% in hearing-impaired individuals. These results indicate that auditory dyssynchrony is not an extremely rare disorder and although only a small portion of the population of children with hearing loss is affected, it is undoubtedly important to detect this disorder so that individualized treatment plans can be devised.

Are cervical vestibular evoked myogenic potentials sensitive to changes in the vestibular system associated with benign paroxysmal positional vertigo

Abstract Objective: This study aimed to correct the notion regarding the efficacy of cervical vestibular evoked myogenic potentials (cVEMP) in identifying benign paroxysmal positional vertigo (BPPV)-associated changes in the peripheral vestibular system. Study design: A static group comparison research design was used to compare the cVEMP results of a group of individuals with BPPV in the age range of 30–60 years against age- and gender-matched healthy individuals. The cVEMP were recorded with tone bursts of 500 Hz gated using a Blackman window. The 95dB nHL tone bursts were presented at the rate of 5.1 Hz. The response was band-pass filtered between 10 and 1500 Hz and amplified by a factor of 5000. The response window was set to 70 ms, which was inclusive of a 15-ms pre-stimulus recording. Results: Responses were analysed for individual peak latencies, peak-to-peak amplitudes, and asymmetry ratio and compared between the groups using mixed analysis of variance and an independent samples t-test. The results revealed no significant difference in the latencies of P13 and N23 (p > 0.05). There was also a lack of difference for peak-to-peak amplitude and asymmetry ratio between the two groups (p > 0.05). Conclusion: There was no difference in the latency or amplitude measures between healthy individuals and the individuals with BPPV, which undermines the utility of cVEMP in identifying changes associated with BPPV in the peripheral vestibular system.

Amplification strategy to enhance speech perception in individuals with auditory neuropathy spectrum disorder

Objective: The present study was conducted to determine if low-cut modified amplification improved aided speech perception compared to standard NAL-NL1 prescriptive amplification in individuals with ANSD. The study further aimed to check the influence of the number of channels in a hearing aid on speech perception with low-cut modification of amplification. Study design: A total of 22 individuals with ANSD in the age range 15–42 years were recruited for the study. The unaided and aided speech identification scores were obtained with standard amplification and low-cut amplification settings in both a four- and a 16-channel digital hearing aid. Results: The results showed that low-cut amplification was slightly better than standard amplification for aided speech perception. Such an improvement could be attributed to the elimination of upward spread of masking during low-cut modification of amplification. In addition, improvement was greater with a four-channel hearing aid compared to a 16-channel hearing aid. Conclusions: The use of low-cut amplification with a low number of channels in the hearing aid for individuals with ANSD is recommended. However, further studies are essential to determine whether the slight improvement in aided scores with a low-cut fitting strategy leads to actual improvement in quality of life.

Tone-evoked brainstem responses and auditory steady state responses to 40hz and 80hz amplitude modulated stimuli with different frequencies - a comparative study

AbstractTone burst evoked auditory brainstem responses and auditory steady state responses with 40 or > 80 Hz modulation can be used to determine frequency specific threshold.AimThe present study was taken up to check for the efficacy of estimating hearing thresholds by tone burst ABR and ASSR. The frequency effect (low, mid and high) on estimating the threshold was also focused upon.Methods20 normal hearing adults (40 ears) in the age range of 16 to 30 years participated in the study. The pure tone audiometry and immittance was initially done. Subsequently, tone-burst ABR, 80Hz ASSR and 40Hz ASSR to estimate the threshold with three frequencies 500Hz (low), 2000Hz (mid) and 4000Hz (high) was done. The data was analyzed statistically using pair sample t-test.ResultsASSR threshold for 80Hz and 40Hz was almost comparable. ASSR was superior to estimate the threshold than tone-burst ABR. For the low frequency the discrepancy between the behavioral threshold and frequency-specific evoked audiometry was more when compared to mid and high frequency.ConclusionPresent study showed that steady-state responses were efficient means of threshold detection than visual detection of ABR wave-V. In awake adult subjects, 40Hz and 80Hz amplitude modulated produced similar results. For the threshold estimation ASSR was better than tone-burst ABR.

Menstrual cycle effects on sacculocollic reflex pathway

Abstract Introduction: Female sex hormones such as oestrogen and progesterone are found to have direct effects in the sensitivity of cochlea, till central auditory cortex by bringing the variation in vascularity in these regions. The aim of the present study was to assess the influence of sex hormones produced during menstrual cycle on the sacculocollic reflex pathway. Method: Twenty female subjects in the age range of 18–25 years with no vestibular pathologies participated in the study. Cervical vestibular evoked myogenic potential test was administered on all the subjects in three phases of menstrual cycle, that is, follicular phase (1–4 days), luteal phase (12–15 days) and menstrual phase (22–25 days). Results: Friedman Chi-square test of difference among repeated measures was done to check the significant differences in mean latency and amplitude values of cVEMP across three phases of menstrual cycle. Although there were differences in the mean latency and amplitude of cVEMP peaks across three phases of menstrual cycle, the statistical analysis revealed no significant effect of different phases of menstrual cycle on the latency or amplitude parameters of cVEMP. Conclusions: There is no significant effect of different phases of menstrual cycle on the latency or amplitude parameters of cVEMP.

Assessment of otolith mediated neural reflexes through cervical and ocular vestibular evoked myogenic potentials in individuals with auditory neuropathy spectrum disorders

Abstract Auditory neuropathy spectrum disorder (ANSD) is characterized by abnormal auditory neural function in the presence of normal cochlear function. Although the presence of vestibular dysfunction has been reported in ANSD through sporadic studies, cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP) were sparingly explored in the same individuals with ANSD. Thus, the present study aimed at investigating otolith modulated neural function in individuals with ANSD. A static group comparison research design was used. cVEMP and oVEMP were elicited by 500-Hz tone bursts from 31 individuals with ANSD and 31 age- and gender-matched healthy controls. Results showed that the response prevalence was less than 20% for both potentials. The present responses were characterized by significant prolongation of later peaks and inter-peak latency intervals and significantly reduced amplitudes compared to the controls (p < 0.001). Both potentials exhibited larger asymmetry ratios compared to the controls, but only cVEMP asymmetry ratio reached a statistically significant level. There was no association of cVEMP and oVEMP response prevalence with the presence of vestibular symptoms. Abnormal or absent responses in the majority of individuals suggest superior and inferior vestibular nerve dysfunction in ANSD. A detailed vestibular evaluation, in addition to the auditory system assessment, is strongly recommended in ANSD.