Interaural Latency Difference Research Articles

Characteristics of Auditory Brainstem Response in Night-shift Health Workers

Background: With technological advancement and economic competitiveness there is an exponential rise in the number of shift workers. Worldwide, healthcare workers constitute the single largest proportion of workers who work on shift duty in order to provide round-the-clock healthcare services to patients. Various studies have demonstrated an association between circadian cycle disturbance due to shift work and adverse health impacts. Purpose: The purpose of the study was to investigate the impact of night shift work on the brainstem-evoked auditory potentials in nursing interns who had been assigned to their first night shift after working day shifts. Methods: A longitudinal, self-case-control study was designed with a sample of 67 nursing interns. Brainstem evoked response audiometry (BERA) had been done after completion of their first posting in Day-shift and then after completion of Night-shift. The paired t-test was used for data analysis. Results: The findings of the study showed significant changes in latencies of wave II ( p < .0001), wave IV ( p < .0001), wave V ( p = .012 & .30), interpeak latency III-V ( p = .009 & .003) and V/I ratio ( p < .0001) for both ears. Conclusions: BERA is an objective non-invasive test to evaluate hearing ability by measuring increased latency and interaural latency difference. After night shift, there were significant changes in auditory acuity which was highly suggestive of delayed transmission in auditory pathway. Hearing impairment has a cascading effect on cognition which may affect night-shift workers’ daily activities and may lead to medical error and risk to patient safety.

Which stimulus should be used for auditory brainstem response in newborns; CE-Chirp® level specific versus Click stimulus.

Auditory Brainstem Response (ABR), the electrical responses in the neuronal pathways extending from the inner ear to the auditory cortex, are evaluated with auditory stimuli. ABR analysis evaluates waves I, III and V's absolute-latencies, amplitude values, interpeak-latencies, interaural-latency differences, and morphologies. This study aims to reveal the advantages of CE-Chirp® LS stimulus and its clinical uses to increase by comparing the amplitude, latency, and interpeak-latency differences of waves I, III, and V at 80dB nHL and wave V at 60, 40, 20dB nHL by using click and CE-Chirp® LS stimuli. 100 (54 boys, 46 girls) infants with normal hearing were included in the National Newborn Hearing Screening Program. With the click and CE-Chirp® LS ABR, the absolute latency and amplitude values of wave V at 20, 40, and 60dB nHL, and the absolute-latency, interpeak-latency, and amplitude values of waves I, III, and V at 80dB nHL are determined between stimuli and right-left ear. When the wave V latency and amplitudes obtained at 80, 60, 40, and 20dB nHL levels were examined between genders, and according to the risk factor, no significant difference was found between click and CE-Chirp® LS stimuli (p>0.05). Waves I, III, and V absolute-latency, amplitudes were compared at 80dB nHL and wave V absolute-latency, amplitudes at 60, 40, and 20dB nHL; the amplitudes measured with CE-Chirp® LS were significantly higher than the click stimulus (p<0.05). When two stimuli were compared for I-III and III-V interpeak-latency values at 80dB nHL level, no significant difference was found between the two stimuli (p>0.05). However, the I-V interpeak-latency value was statistically significantly decreased for two stimuli, regardless of the ear (p<0.05). It is suggested to increase the use of CE-Chirp® LS stimulus with better morphology and amplitude in clinics, believing that it facilitates clinicians' interpretation.

Diagnostic Validity of Auditory Brainstem Response for the Initial Screening of Vestibular Schwannoma.

Background and ObjectivesTo investigate the diagnostic validity of auditory brainstem response (ABR) in the screening of vestibular schwannoma (VS).Subjects and MethodsForty patients diagnosed with VS using magnetic resonance imaging who had undergone ABR before treatment between 2005 and 2015 were included. ABR results were considered positive when findings met at least one of the following criteria: 1) absent evoked response, 2) desynchronization of waves other than wave I, 3) interpeak latency (IPL) between waves I and III >2.5 ms, 4) IPL between waves I and V >4.4 ms, 5) wave V interaural latency difference >0.2 ms, and 6) interaural difference in IPL between waves I and V >0.2 ms.ResultsThe overall sensitivity of ABR was 85.0%. For tumors measuring <10 mm, the sensitivity of ABR was 66.7%, whereas it increased to 90.3% for tumors measuring >10 mm. The sensitivity of tumors confined to the internal acoustic canal was 73.3% compared with 100.0% for tumors confined to the cerebellopontine angle. In patients with serviceable hearing, the mean tumor size was 7.8±2.9 mm in patients with a normal ABR and 15.1±9.4 mm in patients with an abnormal ABR, indicating a significant difference (p<0.05).ConclusionsABR alone is insufficient for the screening of VS, bearing the risk of false-negative outcomes when examining small, intracanalicular tumors. However, ABR can be inexpensively applied for the screening of VS measuring >10 mm in patients with serviceable hearing, supporting the need for further active diagnostic and treatment modalities in clinical practice.

Association between the inter-aural latency difference of brainstem auditory evoked potential wave V and neonatal hyperbilirubinemia

OBJECTIVE To study brainstem auditory evoked potential (BAEP) in neonates with hyperbilirubinemia using short auditory stimuli (60 dBnHL), and to investigate the differences in the inter-aural latency difference (ILD) of wave V between neonates with different total serum bilirubin (TSB) levels. METHODS A prospective study was conducted in neonates with hyperbilirubinemia who were admitted to the Department of Neonatology, Yuhuan People's Hospital of Zhejiang Province, from May 2019 to October 2020. The neonates were divided into a severe group (n=50) and a mild group (n=50) according to their TSB levels. The mild group was divided into two subgroups: 7-10 days (n=20) and 11-14 days (n=20) according to their age. ILD was compared between the neonates with different TSB levels, and its diagnostic value was analyzed. RESULTS Compared with the mild group, the severe group had significantly higher proportions of neonates with abnormal hearing threshold and abnormal ILD (P 0.05). The receiver operating characteristic (ROC) analysis showed that ILD had predictive value for hearing impairment caused by neonatal hyperbilirubinemia (P < 0.05), with an area under the ROC curve of 0.727 as well as a sensitivity of 52.4% and a specificity of 90.9% at the optimal cut-off value of 0.365 ms. CONCLUSIONS Serum bilirubin in neonates affects the ILD of BAEP wave V, especially in those with severe hyperbilirubinemia. ILD at the optimal cut-off value of ≥0.4 ms shows potential value in the diagnosis of hearing impairment caused by neonatal hyperbilirubinemia.

Effect of Stimulus Rates in Chirp and Click Evoked Auditory Brainstem Response in Adults with Normal Hearing Sensitivity

Introduction The effects of increasing stimulus repetition rate on the ABR using click stimuli have been investigated in normal and hearing impaired subjects with neurologic abnormality but there is limited study on the effect of stimulus repetition rate on ABR using chirp stimuli. The present study aims to compare the chirp evoked auditory brainstem responses with reference to changes in latency of peaks, interaural latency differences and interwave latency intervals as a function of rate and compare those responses with the click evoked auditory brainstem responses, in normal hearing subjects. Materials and Methods Total 30 normally hearing adults were considered for this study. All participants were screened for normal hearing sensitivity upto 8 kHz in pure tone audiometry for middle ear pathology and central auditory processing disorder. Four parameters of ABR were considered to assess in this study including absolute latency, interwave latency intervals, latency-rate function and interaural latency. ABR was done based on the protocol of this study. Results Results revealed that there was a significant difference in the absolute latency and interwave intervals when the stimulus repetition rate was increased. Conclusion The latencies of wave III and V increases and waveform morphology changed as the stimulus repetition rate increased above 20/sec. The absolute latency of wave III and V was found to be shorter than clicks and can be used especially in newborn hearing evaluation assuming in shorter time window.

Assessment of cervical and ocular vestibular evoked myogenic potentials in migraine patients

BackgroundPatients suffering from vestibular migraine (VM) are known to have various vestibular test abnormalities interictally and ictally. Recently, vestibular evoked myogenic potentials (VEMPs) have become accepted as a valid method for otolith function assessment. Many studies have identified various vestibular symptoms and laboratory abnormalities in migraineurs. Since migraineurs with no accompanying vestibular symptoms might exhibit subclinical vestibular dysfunction, we investigated vestibular function using ocular and cervical VEMPs in migraine patients. The aim was to study cervical VEMP and occular VEMP in migraineurs with and without vestibular symptoms interictally.ResultsMigraine and VM patients showed significantly longer P13 latency of cVEMP compared to controls. A statistically significant cVEMP interaural P13 latency difference was found in VM compared to healthy controls. Cervical VEMP N23 latency, peak-to-peak amplitude, interaural N23 latency, and amplitude asymmetric ratio did not show any significant difference in migraine and VM patients compared to healthy controls as well as no significant difference across the three groups regarding oVEMP parameters.ConclusionsAbnormal interictal cVEMP results in migraineurs might indicate subclinical vestibulo-collic pathway dysfunction.

The Ototoxic Potential of Cobalt From Metal-on-Metal Hip Implants: Objective Auditory and Vestibular Outcome.

During the past decade, the initial popularity of metal-on-metal (MoM) hip implants has shown a progressive decline due to increasingly reported implant failure and revision surgeries. Local as well as systemic toxic side effects have been associated with excessive metal ion release from implants, in which cobalt (Co) plays an important role. The rare condition of systemic cobaltism seems to manifest as a clinical syndrome with cardiac, endocrine, and neurological symptoms, including hearing loss, tinnitus, and imbalance. In most cases described in the literature, revision surgery and the subsequent drop in blood Co level led to (partial) alleviation of the symptoms, suggesting a causal relationship with Co exposure. Moreover, the ototoxic potential of Co has recently been demonstrated in animal experiments. Since its ototoxic potential in humans is merely based on anecdotal case reports, the current study aimed to prospectively and objectively examine the auditory and vestibular function in patients implanted with a MoM hip prosthesis. Twenty patients (15 males and 5 females, aged between 33 and 65 years) implanted with a primary MoM hip prosthesis were matched for age, gender, and noise exposure to 20 non-implanted control subjects. Each participant was subjected to an extensive auditory (conventional and high-frequency pure tone audiometry, transient evoked and distortion product otoacoustic emissions [TEOAEs and DPOAEs], auditory brainstem responses [ABR]) and vestibular test battery (cervical and ocular vestibular evoked myogenic potentials [cVEMPs and oVEMPs], rotatory test, caloric test, video head impulse test [vHIT]), supplemented with a blood sample collection to determine the plasma Co concentration. The median [interquartile range] plasma Co concentration was 1.40 [0.70, 6.30] µg/L in the MoM patient group and 0.19 [0.09, 0.34] µg/L in the control group. Within the auditory test battery, a clear trend was observed toward higher audiometric thresholds (11.2 to 16 kHz), lower DPOAE (between 4 and 8 kHz), and total TEOAE (1 to 4 kHz) amplitudes, and a higher interaural latency difference for wave V of the ABR in the patient versus control group (0.01 ≤ p < 0.05). Within the vestibular test battery, considerably longer cVEMP P1 latencies, higher oVEMP amplitudes (0.01 ≤ p < 0.05), and lower asymmetry ratio of the vHIT gain (p < 0.01) were found in the MoM patients. In the patient group, no suggestive association was observed between the plasma Co level and the auditory or vestibular outcome parameters. The auditory results seem to reflect signs of Co-induced damage to the hearing function in the high frequencies. This corresponds to previous findings on drug-induced ototoxicity and the recent animal experiments with Co, which identified the basal cochlear outer hair cells as primary targets and indicated that the cellular mechanisms underlying the toxicity might be similar. The vestibular outcomes of the current study are inconclusive and require further elaboration, especially with respect to animal studies. The lack of a clear dose-response relationship may question the clinical relevance of our results, but recent findings in MoM hip implant patients have confirmed that this relationship can be complicated by many patient-specific factors.

Audiological Evaluation of Vestibular Schwannoma Patients with Normal Hearing

Objective: To evaluate the audiological aspects of vestibular schwannoma (VS) patients with normal hearing. Study Design: Retrospective study. Setting: Quaternary referral center for skull base pathologies. Patients: The records on 4,000 patients who had been diagnosed with VS between 1986 and December 2017 were retrospectively reviewed. The patients included in the study were the ones who complied with the strict audiological normality criteria, as follows: a pure tone hearing threshold (at the 6-octave-spaced frequencies from 250 to 8,000 Hz) ≤25 dBHL; a word recognition score >90%; and interaural differences ≤10 dB at each frequency. Interventions: Auditory brainstem response (ABR) testing and radiological imaging. Main Outcome Measures: The incidence of normal objective hearing among VS patients, and the diagnostic utility of the ABR and the effect of tumor size and site on the response. Results: The incidence of normal hearing among VS patients was 4.2%. Tinnitus and vertigo were the most common symptoms across tumor grades; 5.6% of the tumors were large and giant tumors. The ABR yielded a sensitivity of 73.6%, with a false negative rate of 26.3% using a cutoff point of 0.2 ms for interaural latency differences. Conclusions: The diagnosis of VS should not be based on audiometric thresholds alone. Alarming signs of VS should be clear to the physician in order not to miss or delay the diagnosis of the disease. The ABR is useful in the diagnosis of VS, but normal results do not exclude the occurrence of the disease in patients with normal hearing.

Cervical Vestibular Evoked Myogenic Potential in Children with Auditory Neuropathy Spectrum Disorder of prelingual onset

children with ANSD of pre-lingual onset, and to compare c-VEMP findings to those in children with non- ANSD sensorineural (non -ANSD SNHL) of pre-lingual onset.Methods: The study included 35 children with bilateral ANSD, and 32 children with bilateral non-ANSD SNHL of severe, severe to profound, or profound degree. Both groups of children had the onset SNHL pre-lingually. The study also included 15 control children. Mean age and SD were 6.9 years ± 2.9 for the control children, 7.8 years ± 3.1 for the ANSD children, and 8.8 years ± 3.4 for the non-ANSD children. All participant children were subjected to full history taking, otological examination, hearing assessment, recording for auditory brainstem response and cochlear microphonics, Distortion product otoacoustic emission recording, and c-VEMP recording.Results: Results showed that the vast majority of ANSD children (88% of ears) had intact c-VEMP response. Moreover, there was no statistically significant difference between the ANSD children and control children as regards the VEMP parameters (P1-N1 amplitude, asymmetric ratio, P1 latency, N1 latency, and inter-aural latency differences of P1 and N1). There was no statistically significant difference between ANSD with risk factors and those without risk factors as regards VEMP parameters. Results indicate that the vast majority of ANSD children with pre-lingual onset, even those with risk factors, have normal saccular function along with intact and normally functioning inferior vestibular nerve, and the other central connections responsible for the VEMP response. On the other hand, 53.1% of ears children with non-ANSD SNHL had an absent c-VEMP response, and 46.9% of ears had intact and normal c-VEMP response. The overall results indicate that while the pathology of non-ANSD SNHL involves the saccule in more than half of children, the underlying pathology ANSD spares the saccule and its central connection.Conclusions: Results suggest that the site of lesion in ANSD children of pre-lingual onset is restricted to the auditory system with sparing the vestibular system in the majority of children. These findings support the choice of cochlear implantation as the best line of management in children with ANSD, even in the presence of risk factors. So cochlear implantation in children with ANSD is safer than children with SNHL as there will be no fear of bilateral saccular dysfunction in the case saccular damage occurred in the surgery side as a result of the surgical procedure.

Diagnostic Accuracy of Ocular Vestibular Evoked Myogenic Potentials for Superior Canal Dehiscence Syndrome in a Large Cohort of Dizzy Patients.

To determine the diagnostic accuracy of ocular vestibular evoked myogenic potentials (oVEMPs) for superior canal dehiscence syndrome (SCDS) in a large cohort of unselected dizzy patients. Most SCDS patients are dizzy (90%); however, only 30% demonstrate archetypical SCDS clinical proxies (Tullio or Hennebert findings). Several case-control studies have addressed specific SCDS markers using VEMP testing, but the diagnostic value of VEMP for SCDS has not been demonstrated in a target population of dizzy patients. The aim of this study was to confirm the diagnostic properties of oVEMP for SCDS in an unselected cohort of dizzy patients. This diagnostic accuracy study was performed in a tertiary referral center and included a consecutive sample of dizzy patients referred for vestibular function testing. One hundred fifty subjects were collected prospectively; five were excluded due to middle ear disorders, 10 had the target condition (SCDS group), and 135 had an alternative condition (non-SCDS group), based on diagnostic criteria for SCDS used in our department as reference standard. The non-SCDS group was subdivided into diagnostic categories including an "undefined dizziness" group. The index test applied to the total sample (missing data: 1%) consisted of oVEMP recording using three different stimulation modalities, that is, air-conducted (AC) sound stimulation and midsagittal bone-conducted (BC) vibration at both forehead (Fz) and vertex (Cz). Data analysis was conducted on four oVEMP parameters: amplitude, latency, amplitude asymmetry ratio, and interaural latency difference. Between-group analysis was conducted with nonparametric tests. The oVEMP diagnostic accuracy for SCDS was determined with uni/multiparametric receiver operating characteristic analysis. Best cutoff points were computed for those parameters or parameter combinations that showed an accuracy level appropriate for clinical use (area under the curve [AUC] > 0.8). Different oVEMP parameters, in particular, the amplitude to AC stimulation (SCDS: 53, inter quartile range [IQR]: 27.6-68.3 µV; non-SCDS: 4.4, IQR: 2.0-8.1 µV; p < 0.001), were able to separate SCDS from non-SCDS conditions with statistical significance. AC oVEMP amplitude had the highest diagnostic accuracy (area under the curve = 0.96) for SCDS, with optimal sensitivity (100%) and high specificity (89%) at a specific cutoff point (16.7 µV); as an SCDS index, it could distinguish these patients not only from those with other vestibular diagnoses but also from patients with undefined dizziness (sensitivity 100%; specificity 81%). oVEMP was able to identify all subjects affected by SCDS, according to our diagnostic criteria, in a large cohort of unselected dizzy patients. The AC oVEMP amplitude parameter showed optimal sensitivity and high specificity for SCDS and may represent an ideal screening test for SCDS among dizzy patients. This is noteworthy when considering that not all SCDS patients express the clinical key features of vestibular hypersensitivity to sound or pressure change, even though most complain of dizziness.

Evaluation of saccular and inferior vestibular nerve function in children with auditory neuropathy spectrum disorder.

The aim of the current work was to evaluate the function of the saccule and inferior vestibular nerve in children with auditory neuropathy spectrum disorder (ANSD) by recording the cervical-evoked myogenic potentials (C-VEMP) on those children and to compare C-VEMP results in ANSD children of pre-lingual onset to those in ANSD children of post-lingual onset. The study included 38 ANSD children of pre-lingual onset, 16 ANSD children of post-lingual onset, and 20 control children. All participant children were subjected to C-VEMP testing using 500Hz tone burst stimuli. The vast majority of ANSD children of pre-lingual onset (35 out of 38; 92.1%) had bilateral intact C-VEMP response with C-VEMP parameters (amplitude, asymmetric ratio, latency, and inter-aural latency difference) that were not statistically different than those in the control children. Only three children had bilateral absent C-VEMP response. On the other hand, the majority of ANSD children of post-lingual onset (11 out of 16; 68.75%) had bilateral absent C-VEMP response. The remaining five children had bilateral intact C-VEMP response with C-VEMP parameters that were not statistically different than those in the control children. The pathology of ANSD spares the saccule and inferior vestibular nerve in the vast majority of ANSD children of pre-lingual onset, while it involves them in the majority of ANSD of post-lingual onset reflecting different site(s) of lesion between the two ANSD categories. Such results have important clinical implications as regards to the management of ANSD in children.

Audiological findings in children with ataxia-telangiectasia (A-T) syndrome

AimTo assess peripheral and central hearing in children with A-T. Method3 children diagnosed with A-T according to the diagnostic criteria for A-T of the European Society for Immunodeficiencies. Involuntary movements were seen in the form of chorea-athetosis together with tremors. They were examined to assess both peripheral and central hearing was assessed (hearing thresholds). Sound-field testing, tympanometry, acoustic reflexes, Otoacoustic Emissions (OAEs) and Auditory Brainstem Responses (ABR) were done for all of them. ResultsBasic Audiological evaluation is of a limited value as the children are not co-operative. Sound field testing could not be done. Bilateral normal middle ear functions as reflected by Tympanometry and Acoustic Reflexes. Advanced Audiological evaluation including OAEs and ABR are more valuable in assessing hearing in children with A-T. Bilateral pass response at all test frequencies in DPOAEs. Abnormal ABR findings were obtained in the form of a delay in wave V latency more than 2 SD with subsequent increased in I-V interpeak latency with no significant interaural latency difference. ConclusionConsistent with bilateral normal peripheral hearing sensitivity with central hearing affection. LimitationsThe rarity of the disease, make it difficult to be applied on many cases.

Role of cervical vestibular evoked myogenic potentials (cVEMP) and auditory brainstem response (ABR) in the evaluation of vestibular schwannoma

IntroductionCervical vestibular evoked myogenic potentials (cVEMP) can assess the integrity of the inferior vestibular nerve thereby promising to be a useful tool in the audiological test battery to diagnose vestibular schwannoma. ObjectiveTo ascertain the utility of cVEMP in diagnosis of vestibular schwannoma in conjunction with the ABR and to evaluate whether the size of lesion has any effect on the cVEMP measures. MethodsCase-files of 15 known cases of vestibular schwannoma whose pure tone audiometry, auditory brainstem response (ABR), cVEMP and radiological investigation findings were available, were included in the study. Patients were categorised as large or small tumours based on the size. The absolute and inter-peak latencies of ABR, amplitudes of waves V and I, and inter-aural latency difference of wave V of ABR; and latency of P1 and N1 of cVEMP and amplitude of P1–N1 complex were considered in the study. ResultsThere were eight large and nine small tumours. All the patients with large tumours showed significant severity of hearing loss whereas only three out of nine patients with small tumours showed severe to profound deafness in the affected ear. The rest showed hearing status ranging from normal hearing sensitivity to moderate hearing loss. Most of the patients with large tumours showed complete absence of ABR in the affected ears with no identifiable wave-peaks. ABR in small tumours exhibited delayed III–I and delayed V–I interpeak latency interval (IPL). Four out of five patients with large unilateral tumours revealed contralateral effects of reduced amplitude or absence of cVEMP. On the contrary, six out of eight unilateral small tumours showed a normal cVEMP response in the contralateral ear. Both the patients with NF2 in the present study demonstrated cVEMP abnormalities. ConclusionABR and cVEMP, when used in combination, can be of immense use in identification of neuro-otologic conditions such as vestibular schwannoma and bilateral tumours in NF2. In the evaluation of unilateral vestibular schwannoma, abnormal contralateral findings of cVEMP and ABR are strongly indicative of the tumour size >2.5cm. In unilateral severe to profound loss wherein ABR in poorer ear cannot give information of site-of-lesion, cVEMP can help in the differentiation.

Ocular vestibular evoked myogenic potentials to vertex low frequency vibration as a diagnostic test for superior canal dehiscence

To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome. The oVEMP using 125 Hz single cycle bone-conducted vertex vibration were tested in 15 patients with unilateral superior canal dehiscence (SCD) syndrome, 15 healthy controls and in 20 patients with unilateral vestibular loss due to vestibular neuritis. Amplitude, amplitude asymmetry ratio, latency and interaural latency difference were parameters of interest. The oVEMP amplitude was significantly larger in SCD patients when affected sides (53 μVolts) were compared to non-affected (17.2 μVolts) or compared to healthy controls (13.6 μVolts). Amplitude larger than 33.8 μVolts separates effectively the SCD ears from the healthy ones with sensitivity of 87% and specificity of 93%. The other three parameters showed an overlap between affected SCD ears and non-affected as well as between SCD ears and those in the two control groups. oVEMP amplitude distinguishes SCD ears from healthy ones using low-frequency vibration stimuli at vertex. Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems.

Delayed restoration of maximum speech discrimination scores in patients with idiopathic sudden sensorineural hearing loss.

To assess possible delayed recovery of the maximum speech discrimination score (SDS) when the audiometric threshold ceases to change. We retrospectively examined 20 patients with idiopathic sudden sensorineural hearing loss (ISSNHL) (gender: 9 males and 11 females, age: 24-71 years). The findings of pure-tone average (PTA), maximum SDS, auditory brainstem responses (ABRs), and tinnitus handicap inventory (THI) were compared among the three periods of 1-3 months, 6-8 months, and 11-13 months after ISSNHL onset. No significant differences were noted in PTA, whereas an increase of greater than or equal to 10% in maximum SDS was recognized in 9 patients (45%) from the period of 1-3 months to the period of 11-13 months. Four of the 9 patients showed 20% or more recovery of maximum SDS. No significant differences were observed in the interpeak latency difference between waves I and V and the interaural latency difference of wave V in ABRs, whereas an improvement in the THI grade was recognized in 11 patients (55%) from the period of 1-3 months to the period of 11-13 months. The present study suggested the incidence of maximum SDS restoration over 1 year after ISSNHL onset. These findings may be because of the effects of auditory plasticity via the central auditory pathway.

Otologic manifestations of acoustic neuroma

Conclusion: Many patients with acoustic neuroma (AN) experience hearing loss and tinnitus. Time from first symptoms to diagnosis can be considerable. AN should be suspected, and MRI scans performed, in patients with hearing loss accompanied by asymmetry, tinnitus, low speech discrimination score (SDS), and abnormal auditory brainstem response (ABR). Objectives: To determine the otorhinolaryngological factors associated with AN by analyzing the clinical manifestations and diagnostic test results of patients with AN before MRI scanning. Methods: This study enrolled 114 patients definitively diagnosed with AN after visiting the Ear-Nose-and-Throat and Neurosurgery Departments of Kyung Hee University Medical Center from 2001 to 2013. Factors retrospectively analyzed included patient age, gender, major symptoms, accompanying symptoms, symptom duration, pure-tone audiometry, SDS, asymmetry, tinnitogram, ABR, and MRI scan results. Results: The main symptom of AN was hearing loss, and the most frequent accompanying symptom was tinnitus. More severe deafness correlated significantly with lower SDS (p < 0.05). Asymmetric hearing was observed in 75 of 116 patients (64.6%), and mean SDS was 73.1 ± 34.1%. Of patients with latencies of waves I, III, and V on ABR tests, 56.1%, 92.4%, and 92.4%, had interaural latency differences ≥0.2 ms. However, audiometry results did not correlate with lesion site or tumor size (p > 0.05).

Amplitude normalization reduces cervical vestibular evoked myogenic potential (cVEMP) amplitude asymmetries in normal subjects: proof of concept.

The cervical vestibular evoked myogenic potential (cVEMP) is an acoustically synchronized, signal averaged, brief inhibitory response of a contracted muscle usually resulting from an acoustic stimulus. The cVEMP is recorded from the tonically contracted sternocleidomastoid muscle (SCM). The presence and amplitude of the cVEMP is related to both the integrity of the sacculo-collic pathway and magnitude of electromyographic (EMG) activity at the time of recording. Measurement variables include the absolute latency of the primary positive going component (referred to as P13) and interaural (i.e., left versus right) latency differences. Also measured is the peak-to-peak interaural amplitude asymmetry (IAA; percent difference in amplitude, left versus right). It is known that the amplitude of the cVEMP is positively correlated with the magnitude of tonic EMG from which the evoked potential is extracted. Thus, if EMG amplitude is uncontrolled, one cannot determine whether cVEMP asymmetries are occurring due to unilateral end organ disease or asymmetric tonic EMG activity. Two methods have been suggested to control for tonic EMG activity. These include (1) patient self-monitoring of EMG activity with biofeedback and (2) mathematical correction (i.e., amplitude normalization) of the left and right cVEMP waveforms. Currently, it is unknown how effective amplitude normalization techniques are at reducing cVEMP amplitude asymmetry in the presence of varying levels of EMG. The purpose of this investigation was to determine whether the use of amplitude correction techniques would reduce significantly the P13-N23 IAA data in otologically and neurologically intact adults when the level of EMG was varied between right and left sides. A prospective, repeated measures design was used for three different investigations in which cVEMPs were recorded and then processed using amplitude correction. Subjects were 20 otologically and neurologically health young adults between 21 and 29 yr of age. cVEMPs were recorded at four different EMG target levels ranging from 100 to 400 μV. The absolute peak-to-peak amplitude of P13-N23, absolute latency of P13, and the left/right amplitude asymmetry of P13-N23 were measured both with and without the use of EMG amplitude correction techniques. IAAs were calculated using 10 different conditions of varying EMG asymmetry with and without amplitude correction. Data were analyzed using repeated measures analysis of variance (ANOVA) to detect tonic EMG level-dependent differences separately for P13 latency, P13-N23 peak-to-peak amplitude, and mean root mean square (RMS) amplitude cVEMP responses. The amplitude of cVEMP responses from the left and right side were used to calculate IAA for subsequent analyses. Linear regression analyses compared level of tonic EMG with cVEMP amplitude. A one-way multivariate analysis of variance (MANOVA) was used to determine if IAAs were significantly reduced following amplitude correction. Any differences found were investigated using unplanned linear contrasts. The uncorrected cVEMP amplitude and RMS EMG all increased significantly with increases in the EMG target levels. With amplitude correction, cVEMP amplitude did not change significantly with changes in RMS EMG or EMG target levels. These findings suggest that the use of amplitude correction techniques represent an effective method of neutralizing the factor of variability in tonic EMG level on the cVEMP that would be otherwise uncontrolled. Indeed when correction is employed in cases of extreme tonic EMG asymmetry, the upper limit of percent IAA is roughly half of that when EMG correction techniques are not used. Our findings are also in agreement with those of Bogle et al (2013) showing that the input/output growth function for P13/N23 amplitude is not linear but, in fact, saturates at supra-maximal stimulation levels. Accordingly, and contrary to what has been published previously, achieving maximum muscle activation may produce a paradoxically inferior signal-to-noise ratio and in some cases result in an artificially small (or undetectable) corrected cVEMP amplitude. cVEMP amplitude either asymptotes (if maximum EMG amplitude saturation occurs at the same stimulus intensity as yields the maximum cVEMP amplitude), or the cVEMP can become smaller if EMG amplitude can increase further beyond the stimulus intensity that yields that largest P1-N1 amplitude. In the latter case the noise increases further to reach maximum and creates a disadvantageous signal (cVEMP) to noise (tonic EMG) ratio.

Binaural recordings of Auditory Brainstem Response for establishment of normative data and its application in screening patients with symmetrical hearing loss

Background: This article presents clinically important details of recording and evaluating ABR details that will eventually be helpful in standardization of our neurophysiology lab, so that ABR recordings on a routine basis will produce better and meaningful results for interpretation. Aims & Objective: To establish normative data required for recording Auditory Brainstem Response (ABR) using binaural stimulations in children with normal hearing. Materials and Methods: This study was conducted on 40 apparently healthy children with normal hearing. Database was collected following assessment with otological questionnaire, otoscopic examination. BERA was used as a tool for establishment of normative data. Standard test protocol given by Hall was followed for ABR recordings. Results: The Interaural latency difference was less than 0.2 ms (milliseconds) and was found to be in normal limit. Normative data was obtained and the mean values of absolute latencies for left ear were 1.77 ms, 3.73 ms and 5.70 ms respectively and for right ear these were 1.77 ms, 3.76 ms and 5.56 ms respectively. Mean values for amplitude of wave I and V for left ear were 0.36 uV and 0.56 uV respectively. For right values were 0.31 uV and 0.52 uV respectively. Mean values of amplitude ratio (V/I) for left and right ears were 3.06 and 1.80 respectively. Mean values of interpeak latencies of wave I-III, III-V, I-V were 2.01 ms, 2.03 ms and 3.89 ms respectively for left ear and for right ear values were 1.98 ms, 2.02 ms and 3.84 ms respectively. Mean values for left and right ear hearing threshold was 26.25 dBnHL. Conclusion: ABR parameters show variation in values depending upon age, myelination process, maturation of auditory pathway, environmental factors, laboratory setup etc. Hence it is concluded that each laboratory should have its own normative data which can be used as a baseline data for screening of patients with hearing loss.

Characterizing the Effects of Frequency on Parameters of Short Tone-bursts Induced Ocular Vestibular Evoked Myogenic Potentials

Stimulus is the essence of any audiovestibular investigation and ocular vestibular-evoked myogenic potential (oVEMP) would be no different. Several investigations have examined the effect of frequency of stimulus on oVEMP parameters with prime reports concentrated around amplitude and to a lesser extent threshold. Effects of stimulus frequency on latency-related parameters have been sparingly explored with equivocal results. Thus, the aim of this study was to investigate the effects of air-conducted frequency-specific short tone-bursts on latency, amplitude, and threshold-related parameters of various peaks of oVEMP. A normative study was conducted to obtain oVEMP responses from 50 healthy individuals in the age range of 18 - 30 years. Tone-bursts at octave and midoctave frequencies from 250 to 2000 Hz were used to acquire responses from the inferior oblique muscle using contralateral electrode placement. oVEMPs were present in 100% of the individuals at or below the frequency of 1000 Hz. The largest amplitudes and the lowest threshold corresponded to 500 Hz tone-burst, whereas 250 Hz produced largest absolute latencies as well as interpeak latency intervals (P < 0.05). Frequency had no effect on interaural latency difference as well as interaural amplitude ratio. Owing to largest amplitudes and best thresholds, 500 Hz appears better stimuli for clinical recording of oVEMPs. This is true irrespective of the peak complex being assessed is n1p1 or p1n2.

Preoperative Characteristics of Auditory Brainstem Response in Acoustic Neuroma with Useful Hearing: Importance as a Preliminary Investigation for Intraoperative Monitoring

We classified the results of preoperative auditory brainstem response (ABR) in 121 patients with useful hearing and considered the utility of preoperative ABR as a preliminary assessment for intraoperative monitoring. Wave V was confirmed in 113 patients and was not confirmed in 8 patients. Intraoperative ABR could not detect wave V in these 8 patients. The 8 patients without wave V were classified into two groups (flat and wave I only), and the reason why wave V could not be detected may have differed between the groups. Because high-frequency hearing was impaired in flat patients, an alternative to click stimulation may be more effective. Monitoring cochlear nerve action potential (CNAP) may be useful because CNAP could be detected in 4 of 5 wave I only patients. Useful hearing was preserved after surgery in 1 patient in the flat group and 2 patients in wave I only group. Among patients with wave V, the mean interaural latency difference of wave V was 0.88 ms in Class A (n = 57) and 1.26 ms in Class B (n = 56). Because the latency of wave V is already prolonged before surgery, to estimate delay in wave V latency during surgery probably underestimates cochlear nerve damage. Recording intraoperative ABR is indispensable to avoid cochlear nerve damage and to provide information for surgical decisions. Confirming the condition of ABR before surgery helps to solve certain problems, such as choosing to monitor the interaural latency difference of wave V, CNAP, or alternative sound-evoked ABR.