Brainstem Auditory Potentials Research Articles

Evaluation of Brainstem Auditory-Evoked Potentials in Infants with Iron Deficiency Anemia

Purpose: To evaluate and compare the brain functions of infants with and without Iron Deficiency anaemia (IDA) electrophysiologically with brainstem auditory potentials (BAEPs). Materials and Methods: BAEP tests were performed on 26 healthy infants and 26 infants with iron deficiency anaemia, aged 6-24 months, who were followed through the Paediatric Haematology Department at SDU Faculty of Medicine. Children were classified as anaemic if their haemoglobin (Hb) level fell below -2 standard deviations for their age. All patients diagnosed with iron deficiency anaemia received 5 mg/kg/day of divalent iron glycine sulphate complex in three doses daily for a duration of 12 weeks, to be taken on an empty stomach. Both group were orally administered Chloral hydrate at a dosage of 50mg/kg prior to the BAEP test to induce sedation. The BAEP was recorded at a sound intensity level of 90 decibels, with a frequency of 10 Hertz, and with click stimuli ranging from 1000 to 2000. The BAEP test was administered to the IDA group before and after treatment, as well as to the control group, with a 3-month interval between tests. Results: 14 (53.8%) of the IDA patients were males, and 16 (61.5%) of the control group were females. Patients with IDA had an average age of 14.4±3.09 months, while the control group patients have an average age of 11.2±4.04 months. Patients with iron deficiency anaemia had lower pre-treatment levels of Hb, Hct, MCV, MCH, MCHC, transferrin saturation percentage, and ferritin compared to the control group, whereas platelet and RDW values were greater (p˂0.001). The study compared the Brainstem Auditory Evoked Potential (BAEP) values of patients with Iron Deficiency Anaemia (IDA) before treatment with those of control patients. The results indicated that the III-V interval, showing nerve conduction time, was significantly prolonged in the pre-treatment BAEPs (p˂0.05). There was no significant difference in interpeak latencies between the control group and patients with iron deficiency anaemia (IDA) following therapy (p˂0.05). Significant differences were found in the I-III, III-V, and I-V interpeak latencies of individuals with iron deficiency anaemia before and after treatment (p

The Effects of Stimulus Repetition Rate on Electrically Evoked Auditory Brainstem Potentials in Postlingually Deafened Adult Cochlear Implant Recipients.

Background: By using outcome prediction scores, it is possible to distinguish between good and poor performers with cochlear implants (CI) after CI implantation. The reasons for poor performance, despite good basic conditions, can be manifold. On the one hand, the postoperative fitting may be inadequate; on the other, neurophysiological disease processes may impair speech understanding with a CI. These disease processes are not yet fully understood. In acoustics, it is known that the auditory brainstem responses (ABR) and their latencies and amplitudes allow differential diagnosis based on reference values for normal-hearing individuals. The aim of this study was to provide reference values for electrically evoked brainstem responses (EABRs) in terms of rate-dependent latencies and amplitudes. Methods: 20 ears of 18 experienced adult CI recipients with a predicted and measured good postoperative word recognition score were recruited from the clinic's patient pool. In the same stimulation mode and intensity we measured latencies and interpeak-latencies of EABRs and electrically evoked compound action potentials (ECAPs). With a defined supra-threshold stimulation intensity above the individual ECAP threshold, we applied stimulation at several rates between 11 and 91 stimuli per second. Results: We found rate dependences for EABR latency t3 and t5 in the order of 0.19 ms and 0.37 ms, respectively, while ECAP was not affected by rate. Correspondingly, the interpeak intervals' rate dependences for t5-t1, t5-t3 and t3-t1 were of the order of 0.37 ms, 0.18 ms and 0.19 ms. Comparing the EABR amplitudes between the stimulation rates 11/s and 81/s, we found that at 81/s the amplitudes were significantly reduced down: to 73% for A3 and 81% for A5. These rate dependences of latency and amplitude in EABR have characteristics comparable to those of acoustic ABR. Conclusions: These data may serve to provide reference values for EABR and ECAP latencies, interpeak intervals and amplitudes with respect to stimulation rate. Altered response patterns of ECAPs and EABRs to normalised stimulation modes could be used in the future to describe and classify neuropathological processes in a better-differentiated way.

Evaluation of an Investigational Hearing Screening Device (HeLe) to Demonstrate Acoustic Brainstem Response among Normal-hearing Adults

Objective. This pilot human trial demonstrates the ability of the investigational newborn hearing screening device to provide acoustic stimulation to produce evoked potentials, as well as its ability to capture and acquire auditory evoked potentials, especially the auditory brainstem response (ABR) wave V. This pilot study also demonstrates the ease of recognizing and identifying ABR waves in the graphical presentation of the evoked potentials over time.Methods. Fourteen normal-hearing adults or a total of twenty-eight (28) normal-hearing adult ears underwent auditory brainstem response testing using the investigational hearing screening device. A commercially available auditory brainstem response detection device was used to confirm that the acquired ABR waves of the investigational device are normal. The ABR waves displayed by the investigation device were also reviewed by the clinical audiologists to determine their recognizability and identifiability.Results. The pilot trial demonstrates the ability of the investigational newborn hearing screening device in providing acoustic stimulation to produce evoked potentials, and in acquiring and capturing ABR waves, specifically the wave V, among normal-hearing adult ears. The clinical audiologists recognized and identified the ABR wave V among the evoked potentials at 40dB, 60dB, and 80dB acoustic stimulation. About eighty-nine percent (89.2%) of all ears tested had identifiable and recognizable wave V upon acoustic stimulation at 40dB.Conclusion. The investigational hearing screening device: (1) can provide acoustic stimulation to produce evoked potentials, (2) can accurately capture and acquire these evoked potentials, (3) can present these evoked potentials in a voltage per time graphical display which an audiologist and trained HCP can easily read and interpret (diagnostic ABR), and (4) can present wave V auditory brainstem potentials that can be easily identified by an audiologist and trained HCP (screening ABR).Keywords: ,

Study of auditory pathways in type 1 diabetes mellitus through brainstem auditory evoked potentials and contralateral acoustic reflex.

To investigate the functionalities of the neural pathways through the auditory evoked potentials of the brainstem and the contralateral stapedial acoustic reflexes in normal-hearing individuals with type 1 diabetes mellitus, in order to detect possible alterations in the central auditory pathways. This is a cross-sectional study with a comparison group and a convenience sample, consisting of 32 individuals with type 1 diabetes mellitus and 20 controls without the disease. All subjects had hearing thresholds within normal limits and type A tympanometric curves. The acoustic reflex arc and brainstem auditory potentials were investigated. Statistical analyses were performed using the SPSS 17.0. The Chi-square test, Student´s t-test, and Multiple linear regression were used. The auditory thresholds of the acoustic reflex were statistically lower in the group with the disease at frequencies of 0.5 kHz and 1.0 kHz in the left ear (p=0.01 and p=0.01, respectively). The absolute latencies III and V of the auditory potentials of the brainstem in the right ear and V in the left ear were increased in subjects with type 1 diabetes mellitus (p=0.03, p=0.02 and p=0.03, respectively). The findings suggest that subjects with type 1 diabetes mellitus are more likely to present alterations in the central auditory pathways, even with auditory thresholds within normal limits.

WYNIKI OBSERWACJI PACJENTÓW Z NEUROFIBROMATOZĄ TYPU 1 PO FORMALNYM TRENINGU SŁUCHOWYM

BackgroundThe aim was to electrophysiologically evaluate changes in the peripheral and central auditory systems in individuals with neurofibromatosis type 1 who underwent formal auditory training.Material and methodsThe sample consisted of 6 individuals aged between 9 and 15 years. The procedures involved anamnesis, meatoscopy, brainstem auditory potentials and long-latency evoked potentials, and behavioral tests of central auditory processing. All individuals were given 9 weekly sessions of formal auditory training.ResultsAfter therapeutic intervention we observed improved performance in auditory closure (<i>p</i> = 0.014) and figure–background discrimination for verbal sounds (<i>p</i> = 0.025). There were no significant changes in brainstem auditory evoked potentials. However, the P300 of the longlatency auditory evoked potential showed significant differences for the left ear in terms of latencies of waves N2 (<i>p</i> = 0.05) and P3 (<i>p</i> = 0.05) and the amplitude of N2–P3 (<i>p</i> = 0.05).ConclusionsTherapeutic intervention by means of formal auditory training is effective in rehabilitating central auditory processing disorder. There were improved responses in both behavioral and electrophysiological assessments, which were maintained for at least 4 months.

Simultaneous measurement of human auditory nerve and brainstem potentials: Effects of upward spread of excitation

Acoustic clicks evoke strong synchrony of auditory-nerve (AN) fibers, thereby eliciting a compound action potential (CAP); however, synchrony is reduced by the delay of the cochlear traveling wave. Upward-frequency chirps compensate for this delay, resulting in larger CAPs evoked by chirps than clicks. Our model simulations of CAPs suggest that chirps presented at high intensities (100 dB peSPL) adapt basal AN fibers via upward spread of excitation of low-frequency chirp components. This adaptation results in less-than-or-equal-to CAP amplitudes and distorted CAP morphology compared to CAPs evoked by clicks. Simulations show that these effects on CAP amplitude and morphology can be avoided by reducing the amplitude of the low-frequency components of the chirp (i.e., modified chirp). Here we present CAPs from 12 young adults with NH, which for high stimulus intensities, exhibit reduced amplitudes and broader CAP morphology for chirps than clicks, whereas CAP amplitudes for modified chirps exceed those for clicks, consistent with model simulations. The distorted CAP morphology in response to high-level chirps is consistent with adaptation of AN responses and broad cochlear excitation. Interestingly, the deleterious effects of high-level chirps on CAP amplitude and morphology are reduced or absent in simultaneous recordings of the auditory brainstem response.

Opioid modulation of cochlear auditory responses in the rat inner ear.

The auditory system has an extensive efferent innervation, which contributes to processes of control and regulation of the afferent input. The expression of receptors to various neurotransmitters and neuropeptides in the inner ear has been described, among which endogenous opioid receptors are found. The role of opioid receptors in the cochlea is not yet fully defined, it has been reported that opioid agonists and antagonists modulate the response to auditory stimuli and in clinical practice, multiple cases have been reported in which the consumption of opioid derivatives induce sensorineural hearing loss. In this work, we evaluated the effects of acute treatment with morphine, fentanyl, tramadol, and naloxone, in the auditory brain stem potentials (ABR), the compound action potential (CAP), and distortion products otacoustic emissions (DPOAE), across a wide range of stimulus frequencies and amplitudes. Adult Long-Evans rats of the strain CII/ZV weighing 180-220g were used. For the ABR recording drugs were administered intraperitoneally or intravenously. For the CAP and DPOAE drugs were applied by direct perfusion in the middle ear. The opioid agonists produced a consistent increase in the amplitude of the PI component of the ABR and of the N1-P1 amplitude of the CAP. Naloxone produced no significant changes in the ABR and a reduction of the CAP N1-P1 amplitude. Also, opioid agonists induced a decrease in the amplitude of the DPOAE. These results show that the opioid receptor activation modulates both the afferent response at both the afferent response to acoustic stimuli, and also at the cochlear mechanics as revealed by DPOAE changes. These results present a significant step in understanding how opioid modulation of auditory responses may contribute to the auditory processing and to sensorineural hearing loss produced by opioids.

Electrically Evoked Auditory Brainstem Response over Round Window by Bipolar Stimulation

Auditory brainstem potentials can be elicited by electrical stimulation of the round window (RW). In this technique, extracochlear stimulation is objectively used in the selection of cochlear implant (CI) candidates to avoid cochlear damage. However, until now, its use is limited due to the large artifacts generated by electrical stimulation. Our objective was to obtain reliable and reproducible electrically evoked auditory brainstem responses (eEABRs) using a new method of stimulation. This was a prospective study including subjects who underwent electrical stimulation on RW during CI surgery between 2013 and 2016. A "Stimulator Box," which produces electric stimuli identical to those provided by a CI, and an evoked potential recording equipment were used. The results obtained with monopolar and bipolar electrodes were compared. RW eEABR recordings of 49 subjects (mean age, 34 years) were characterized by their stability and by having wave V between 3 and 5.5 ms. A higher percentage of responses were obtained on increasing the phase duration instead of the pulse amplitude. A significantly greater percentage of positive responses were obtained using bipolar stimulation than using monopolar stimulation (p<0.001). Using extracochlear electrical stimulation technique, described herein, and bipolar electrical stimulation probe allows for reliable and reproducible eEABR recordings in CI candidates.

The effect of interaural timing on the posterior auricular muscle reflex in normal adult volunteers

The posterior auricular muscle (PAM) reflex to sounds has been used clinically to determine hearing threshold as an alternative to other audiological diagnostic measures such as the auditory brainstem response. We have shown that the PAM response is also sensitive to interaural timing differences in normally hearing adults. PAM responses were evoked by both ipsilateral/ contralateral monaural stimulation and by binaural stimulation. Introducing sound delays ipsilaterally or contralaterally decreased the PAM response amplitude and increased its latency. The PAM response in this study shows a qualitatively similar pattern to that seen by the binaural interaction component (BIC) of the auditory brainstem potential to binaural clicks described in previous studies, in that both: have their shortest latency and maximal amplitudes centred around zero interaural timing differences, have response latencies increase with increasing interaural delays up to 1.2 ms and have response amplitudes decrease with increasing interaural delays of up to 1.2 ms. Our data show that the PAM response may be useful in measuring binaural integration in humans non-invasively for diagnostic or research studies.

S11-4. Deviance-related responses along the auditory hierarchy in the brain

In electrophysiological research, automatic auditory deviance detection has traditionally been associated with mismatch negativity (MMN), a component of the auditory evoked potential (AEP), peaking at 100–250 ms from stimulus onset. However, a series of recent studies have revealed that MMN may no longer represent the earliest electrophysiological response of auditory change detection in human, as shown by deviant modulated middle latency responses (MLRs), peaking at latencies 20–50 ms after stimulus onset. Recently, early correlates of deviance detection can be seen in the frequency following response (FFR), a sustained component of the auditory brainstem potential that is phase-locked to the periodic characteristics of the eliciting stimulus. Here, amplitude modulated sounds were presented to healthy subjects in a frequency oddball paradigm, and deviance-related responses were elicited in the FFR and MLR, as well as the long latency response (LLR), reflected by MMN. These findings demonstrate that different levels along the auditory hierarchy show auditory deviations from a regular sound sequence in one single recording protocol.

Audiograms of three subterranean rodent species (genus Fukomys) determined by auditory brainstem responses reveal extremely poor high-frequency hearing.

Life underground has shaped the auditory sense of subterranean mammals, shifting their hearing range to low frequencies. Mole-rats of the genus Fukomys have, however, been suggested to hear at frequencies up to 18.5 kHz, unusually high for a subterranean rodent. We present audiograms of three mole-rat species, Fukomys anselli, Fukomys micklemi and the giant mole-rat Fukomys mechowii, based on evoked auditory brainstem potentials. All species showed low sensitivity and restricted hearing ranges at 60 dB SPL extending from 125 Hz to 4 kHz (5 octaves) with most-sensitive hearing between 0.8 kHz and 1.4 kHz. The high-frequency cut-offs are the lowest found in mammals to date. In contrast to predictions from middle ear morphology, F. mechowii did not show higher sensitivity than F. anselli in the low-frequency range. These data suggest that the hearing range of Fukomys mole-rats is highly restricted to low frequencies and similar to that of other subterranean mammals.

Correction: Audiograms of three subterranean rodent species (genus Fukomys) determined by auditory brainstem responses reveal extremely poor high-frequency cut-offs.

ABSTRACT Life underground has shaped the auditory sense of subterranean mammals, shifting their hearing range to low frequencies. Mole-rats of the genus Fukomys have, however, been suggested to hear at frequencies up to 18.5 kHz, unusually high for a subterranean rodent. We present audiograms of three mole-rat species, Fukomys anselli, Fukomys micklemi and the giant mole-rat Fukomys mechowii, based on evoked auditory brainstem potentials. All species showed low sensitivity and restricted hearing ranges at 60 dB SPL extending from 125 Hz to 4 kHz (5 octaves) with most-sensitive hearing between 0.8 kHz and 1.4 kHz. The high-frequency cut-offs are the lowest found in mammals to date. In contrast to predictions from middle ear morphology, F. mechowii did not show higher sensitivity than F. anselli in the low-frequency range. These data suggest that the hearing range of Fukomys mole-rats is highly restricted to low frequencies and similar to that of other subterranean mammals.

68. Brainstem auditory evoked potentials in children 2–5 years of age with language delays

Introduction Language delay (LD) is a common problem in childhood, the auditory brainstem potentials (ABP) are necessary for early diagnosis. Objetive To describe the abnormalities in auditory brainstem potentials in children 2–5 years with LD. Methodology Transversal study, 50 children, 2–5 years of age, with LD, no history of neurological illness, underwent ABP, evaluating morphology (V/I), absolute latencies of waves I, III and V; interpeak latencies I–III, III–V and I–V, expressed in milliseconds (ms) and hearing threshold expressed in decibels (dB). Results We included 50 patients, 66% boys and 34% girls. In 90% of the ABP there was a reversal V/I ratio. Absolute latencies, conduction intervals and the hearing threshold were normal in all cases. Conclusion The altered morphology of ABP (inversion of the relationship V/I) was related with dysfunction of the inferior colliculus (generator V wave), so it is proposed to complement the evaluation with middle latency responses and logo-audiometry. Significance Early diagnosis and intervention in the management of these children is important to enhance language maturation.

P54. New electrodes for routine intra-operative dual near-field (DNF) monitoring of the cochlear nerve

Purpose Intraoperative near-field recording of cochlear and brainstem auditory potentials (BAEP) can significantly reduce acquisition time ( Matthies and Samii, 1997 ; Moller et al., 1994 ). Over a period of 15 years we have designed and tested tympanic and brainstem electrodes to monitor the functional integrity of the lower auditory pathway (cochlea, cochlear nerve, brain stem) during surgery in the cerebello-pontine angle (CPA) and the internal auditory canal. Method For routine application, a ball-shaped design has proven to be most advantageous and was developed with a company (inomed Medizintechnik, Emmendingen, Germany). Currently, two stainless steel mini-ball electrodes are employed. One of them is connected to a stainless-steel spring reaching out of an insert earphone and attaches to the tympanic membrane (ECoG, Krieg et al., 2014 ). A second mini-ball electrode with a diameter of 1.6 mm can be placed on the cochlear nerve or at the dorsal cochlear nucleus of the brainstem to record a central auditory brainstem response (CABR). These electrodes were applied in more than 500 patients with lesions in the CPA and internal auditory canal during microsurgery. Near-field potentials have been compared to the far-field auditory brainstem response (ABR, Cz-A1/A2, band-pass 100–3000 Hz). Click stimuli were applied at 13.2 Hz. Data processing was carried out with a commercially available electrophysiological monitoring system (ISIS®, inomed). Results Electrode impedance was consistently lower than 5 kOhm at 1 kHz. Because of its ball shape, the intracranial electrode could easily be placed in the lateral recess of the fourth ventricle (dorsal cochlear nucleus, DCN) and on the cochlear nerve without having to pay attention to a specific contact area on its surface ( Fig. 1 ). If necessary, it was slid out just as easy. Waves I and II of the BAEP were best identified in recordings at the tympanic membrane, wave III to V were largest in recordings with the mini-ball electrodes at the brainstem or on the cochlear nerve. Compared to far-field ABR, amplitudes were 3–4 times larger for ECoG, and 2–20 times larger for CABR in patients with functional hearing ( Fig. 2 ). CABR was more variable than the ECoG, depending mostly on electrode location relative to the brainstem generators. With optimal placement of the electrodes, reliable BAEP averages were obtained within 40 s in far-field, and within less than 10 s in near-field recordings. Conclusions Electrodes developed for near-field recording on both ends of the cochlear nerve allow for an almost instantaneous feedback on the integrity of hearing. Dual near-field (DNF) recording is significantly superior to standard auditory far-field monitoring.

Auditory N1-P2 Cortical Event Related Potentials in Auditory Neuropathy Spectrum Disorder Patients

OBJECTIVE: The purpose of this study was to determine whether a group of patients with auditory neuropathy have abnormal changes in auditory N1-P2 and to analyze the results in those patients and compare them with matched group of normal subjects. MATERIALS and METHODS: Cortical auditory evoked potentials were obtained from nine female and seven male patients with auditory neuropathy, ranging in age from 19 to 48 years. The control group comprised 15 (9 males and 6 females) age-matched, normally hearing adults. Cortical auditory evoked potentials were recorded in both groups. Audiological assessments were performed in both groups, which included pure tone audiometry, speech audiometry, tympanometry, acoustic reflex, distortion products otoacoustic emissions, as well as auditory brainstem potential testing. RESULTS: N1-P2 amplitudes were reduced and latencies were prolonged in the study group, and these parameters were found to be statistically significant when compared to normal subjects (p<0.05). CONCLUSION: The neurophysiologic measures of auditory processing-i.e., N1-P2 response to tonal frequency stimuli-in auditory neuropathy spectrum disorder patients are found to be different. Hence, arguing a doubt on the affection of hypothesize origin of the N1-P2 potential in ANSD

Conjunct SEP and MEP monitoring in resection of infratentorial lesions: lessons learned in a cohort of 210 patients.

During the surgical removal of infratentorial lesions, intraoperative neuromonitoring is mostly focused on cranial nerve assessment and brainstem auditory potentials. Despite the known risk of perforating vessel injury during microdissection within the vicinity of the brainstem, there are few reports about intraoperative neuromonitoring with somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) assessing the medial lemniscus and corticospinal tract. This study analyses the occurrence of intraoperative changes in MEPs and SEPs with regard to lesion location and postoperative neurological outcome. The authors analyzed 210 cases in which patients (mean age 49 ± 13 years, 109 female) underwent surgeries involving the skull base (n = 104), cerebellum (n = 63), fourth ventricle (n = 28), brainstem (n = 12), and foramen magnum (n = 3). Of 210 surgeries, 171 (81.4%) were uneventful with respect to long-tract monitoring. Nine (23%) of the 39 SEP and/or MEP alterations were transient and were only followed by a slight permanent deficit in 1 case. Permanent deterioration only was seen in 19 (49%) of 39 cases; the deterioration was related to tumor dissection in 4 of these cases, and permanent deficit (moderate-severe) was seen in only 1 of these 4 cases. Eleven patients (28%) had losses of at least 1 modality, and in 9 of these 11 cases, the loss was related to surgical microdissection within the vicinity of the brainstem. Four of these 9 patients suffered a moderate-to-severe long-term deficit. For permanent changes, the positive predictive value for neuromonitoring of the long tracts was 0.467, the negative predictive value was 0.989, the sensitivity was 0.875, and the specificity 0.918. Twenty-eight (72%) of 39 SEP and MEP alterations occurred in 66 cases involving intrinsic brainstem tumors or tumors adjacent to the brainstem. Lesion location and alterations in intraoperative neuromonitoring significantly correlated with patients' outcome (p < 0.001, chi-square test). In summary, long-tract monitoring with SEPs and MEPs in infratentorial surgeries has a high sensitivity and negative predictive value with respect to postoperative neurological status. It is recommended especially in those surgeries in which microdissection within and in the vicinity of the brainstem might lead to injury of the brainstem parenchyma or perforating vessels and a subsequent perfusion deficit within the brainstem.

31. Intraoperative neurophysiological monitoring for lesions in infratentorial surgery with particular emphasis on long tract functions

During the surgical removal of infratentorial lesions intraoperative neuromonitoring is mostly focused on cranial nerves and brainstem auditory potentials. Despite the known risk of perforating vessel injury during microdissection within the vicinity of the brainstem, there are few reports about intraoperative neuromonitoring with somatosensory (SEP) and motor (MEP) evoked potentials assessing the medial lemniscus and corticospinal tract. This study analyses the occurrence of intraoperative changes in MEP and SEP with regard to lesion location and postoperative neurological outcome. 210 patients (49 ± 13 years, 109 female) undergoing surgeries within the vicinity of the cerebello-pontine angle (77), cerebellum (59), brainstem (40), skull base tumours (26) and others (5) were analysed. 171/210 (81.4%) surgeries were uneventful for long-tract monitoring. 9/39 SEP and MEP-alterations (23%) were transient and without neurological long-term sequelae. Permanent deterioration was seen in 19/39 patients (49%), of which 4 were related to tumour dissection and followed by slight permanent neurological deficit. 11 patients (28%) encountered losses of at least one modality, which were related to surgical microdissection within the vicinity of the brainstem in 9 patients. 4/9 patients suffered a severe long-term deficit. Overall, positive predictive value for long tract neuromonitoring was 0.394, negative predictive value 0.994, sensitivity 0.934 and specificity 0.886. 28/39 (71%) SEP- and MEP-alterations occurred in 66 brainstem respective skull base tumours compared to 11/39 (29%) alterations in all other 144 locations. Tumour location and alterations in intraoperative neuromonitoring significantly correlated with patient outcome (p < 0.001, chi-square test). In summary, long tract monitoring with SEPs and MEPs in infratentorial surgeries has a high sensitivity and negative predictive value indicating postoperative neurological status. It is recommended especially in those surgeries where microdissection within the vicinity of the brainstem might lead to injury of perforating vessels and subsequent perfusion deficit within the brainstem.

Audiological findings in pediatric perineal allergic rhinitis (house dust mite allergy) patients

Allergic rhinitis is the type 1 hypersensitivity reaction of the nasal mucosa and its primary mediator is Ig E. It is most frequently observed in children and adolescents. Our purpose in this study is to investigate the impact of allergy on hearing functions in children with perineal allergic rhinitis (house dust mite allergy). 50 perineal allergic rhinitis (house dust mite allergy) patients (33 male, 17 female patients, aged between 6 and 15, average age 10.4) and 20 control patients (12 male, 8 female, aged between 6 and 15, average age 11.2) underwent high frequency pure tone audiometry, acoustic reflex, otacoustic emission (OAE) and auditory brainstem potentials to assess their auditory functions. No statistically significant difference was detected between the study group and the control group with respect to their hearing thresholds (250-16,000Hz). No statistically significant difference was detected as a result of the comparison between the study group and control group in terms of their signal-noise ratios at Distortion Product OAE in all frequencies (996-8,004Hz). No statistically significant difference was detected between the study group and the control group in terms of the 1st, 3rd and 5th wave latencies and 1-3, 3-5 and 1-5 inter-peak values. This study is the first study where the audiological functions of the pediatric perineal allergic rhinitis (house dust mite allergy) patients were assessed. No significant difference was detected between the group of pediatric perineal allergic rhinitis (house dust mite allergy) patients and the control group with respect to their audiological functions.

Auditory neuropathy spectrum disorder: Its prevalence and audiological characteristics in an Indian tertiary care hospital

ObjectiveAuditory neuropathy spectrum disorder (ANSD) has become a well accepted clinical entity. ANSD has now become easy to recognize with advent of test battery approach for hearing loss evaluation. However, little is known about its epidemiology and aetiology, especially its prevalence and incidence in India. This study was conducted to determine the prevalence and audiological characteristics of ANSD in our tertiary care hospital at New Delhi, India. MethodsWe prospectively enrolled all the paediatric cases i.e. less than 12years of age referred to our outpatient department for hearing evaluation. All the cases were evaluated using complete audiological test battery consisting of pure tone audiometry (PTA), impedance audiometry, acoustic reflexes, otoacoustic emissions (OAE), and brain stem evoked response audiometry (BERA). The instrument used was GSI Audera. BERA with both condensation and rarefaction polarity was performed in cases with absent wave V even at highest intensity levels. The criteria used for diagnosis of ANSD was normal or near normal cochlear hair cells (sensory) function (preservation of otoacoustic emissions and/or cochlear microphonics) and absent or abnormal auditory nerve function (absent or severely abnormal auditory brainstem potentials). A repeat test battery was performed after 3months on the diagnosed cases of auditory neuropathy. Based on their behavioural findings the appropriate management programme was formulated. ResultsA total of 487 paediatric cases were referred for hearing evaluation. 183 (37.6%) cases showed absent BERA and 26(5.3%) cases fulfilled the diagnostic criteria for ANSD. Repeat examination after 3months revealed presence of OAE's in 57.6% (15/26) cases while cochlear microphonics were present in all the 26 cases. ConclusionThe prevalence of ANSD in our study is 5.3% and in children diagnosed with severe to profound hearing loss is 14%. Presence of cochlear microphonics with absent BERA seems to be reliable criteria for diagnosing ANSD.

Limitations in the Rapid Extraction of Evoked Potentials Using Parametric Modeling

The rapid extraction of variations in evoked potentials (EPs) is of great clinical importance. Parametric modeling using autoregression with an exogenous input (ARX) and robust evoked potential estimator (REPE) are commonly used methods for extracting EPs over the conventional moving time average. However, a systematic study of the efficacy of these methods, using known synthetic EPs, has not been performed. Therefore, the current study evaluates the restrictions of these methods in the presence of known and systematic variations in EP component latency and signal-to-noise ratios (SNR). In the context of rapid extraction, variations of wave V of the auditory brainstem in response to stimulus intensity were considered. While the REPE methods were better able to recover the simulated model of the EP, morphology and the latency of the ARX-estimated EPs was a closer match to the actual EP than than that of the REPE-estimated EPs. We, therefore, concluded that ARX rapid extraction would perform better with regards to the rapid tracking of latency variations. By tracking simulated and empirically induced latency variations, we conclude that rapid EP extraction using ARX modeling is only capable of extracting latency variations of an EP in relatively high SNRs and, therefore, should be used with caution in low-noise environments. In particular, it is not a suitable method for the rapid extraction of early EP components such as the auditory brainstem potential.