Brainstem Auditory Evoked Potentials Changes Research Articles

A phase 2a study investigating the effects of ritlecitinib on brainstem auditory evoked potentials and intraepidermal nerve fiber histology in adults with alopecia areata.

Reversible axonal swelling and brainstem auditory evoked potential (BAEP) changes were observed in standard chronic (9-month) toxicology studies in dogs treated with ritlecitinib, an oral Janus kinase 3/tyrosine kinase expressed in hepatocellular carcinoma family kinase inhibitor, at exposures higher than the approved 50-mg human dose. To evaluate the clinical relevance of the dog toxicity finding, this phase 2a, double-blind study assessed BAEP changes and intraepidermal nerve fiber (IENF) histology in adults with alopecia areata treated with ritlecitinib. Patients were randomized to receive oral ritlecitinib 50 mg once daily (QD) with a 4-week loading dose of 200 mg QD or placebo for 9 months (placebo-controlled phase); they then entered the active-therapy extension and received ritlecitinib 50 mg QD (with a 4-week loading dose of 200 mg in patients switching from placebo). Among the 71 patients, no notable mean differences in change from baseline (CFB) in Waves I-V interwave latency (primary outcome) or Wave V amplitude on BAEP at a stimulus intensity of 80 dB nHL were observed in the ritlecitinib or placebo group at Month 9, with no notable differences in interwave latency or Wave V amplitude between groups. The CFB in mean or median IENF density and in percentage of IENFs with axonal swellings was minimal and similar between groups at Month 9. Ritlecitinib treatment was also not associated with an imbalanced incidence of neurological and audiological adverse events. These results provide evidence that the BAEP and axonal swelling finding in dogs are not clinically relevant in humans.

Brainstem auditory evoked potentials in microvascular decompression for hemifacial spasm: A prospective study

ObjectiveThe aim of this prospective study is to identify the factors influencing postoperative hearing loss (HL) and explore effective strategies for reducing postoperative hearing complications following microvascular decompression (MVD) for hemifacial spasm (HFS). MethodsFrom January 2018 to January 2023, we enrolled a total of 55 patients who underwent MVD for HFS at our institution. Intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) was conducted in all surgeries, beginning from the induction of general anesthesia and continuing until skin closure. Prior to surgery and one month after, pure-tone audiometry (PTA) evaluations were performed to evaluate HL. We conducted an analysis to identify factors that influenced postoperative HL. Our examination focused on the occurrence of postoperative HL, considering changes in BAEPs, and we evaluated the diagnostic accuracy of significant warning criteria. ResultsIn this study, a total of 55 patients (37 women and 18 men) with a mean age of 52.5 ± 13.4 years (range 24–80) were included. Among them, 5 patients (9.1 %) experienced postoperative HL. The variations in other risk factors based on the pattern of HL were not statistically significant (p > 0.05), whereas surgical experience showed significance (p = 0.028). Notably, the group of patients who showed wave V loss in intraoperative BAEPs was found to be significantly associated with postoperative HL. ConclusionSurgical experience is a factor influencing postoperative HL. Intraoperative changes in BAEPs, particularly loss of wave V, were found to be a significant indicator of poorer recovery of hearing capacity after MVD for HFS.

Patogenesis of tinnitus in patients with post-COVID syndrome - preliminary report.

<b><br>Introduction:</b> Similarly to hearing loss and dizziness, tinnitus is a frequently reported complication of COVID-19 and remains the subject of numerous scientific reports. However, the exact impact of SARS-CoV-2 on the pathophysiology of tinnitus observed in post-COVID syndrome remains unclear. One suspected cause behind the development of vestibulocochlear symptoms is the inflammation of neural tissue triggered by SARS-CoV-2 infection.</br> <b><br>Aim:</b> The aim of this study was to analyze the results of Brainstem Auditory Evoked Potentials (BAEP) in the context of tinnitus development among patients diagnosed with post-COVID syndrome.</br> <b><br>Material and methods:</b> This retrospective study involved the analysis of BAEP test results of patients admitted to the Audiology Clinic of the Military Institute of Medicine at the National Research Institute and diagnosed with the post-COVID syndrome. The study compared the average latency values of waves I, II, III, IV, V, and intervals I-III, III-V, I-V. The statistical analysis of the obtained data was performed.</br> <b><br>Results:</b> Out of 18 patients (9 female, 9 male) with an average age of 54.22 years (9.65) diagnosed with post-COVID syndrome, tinnitus was identified in 5 individuals (27.78%). A statistically significant increase in wave V latency (5.98 vs. 5.63 [ms]; P < 0.05) and interval III-V (1.99 vs. 1.71 [ms]; P<0.05) was observed between the groups of patients with and without tinnitus.</br> <b><br>Discussion:</b> Study results analyzing BAEP changes in patients with post-COVID syndrome in the context of tinnitus are insufficient in current literature. The only available report linking post-COVID syndrome with sensorineural hearing loss demonstrated a statistically significant increase in latency values of waves III, V, and an increase in intervals I-III, III-V.</br> <b><br>Conclusions:</b> Tinnitus in patients suffering from post-COVID syndrome may be related to prolonged conduction of nerve impulses within the brainstem auditory pathway. Detailed pathophysiology of these changes requires further research.</br&gt.

Evaluation Value of Brainstem Auditory Evoked Potentials in Rehabilitation of Children with Developmental Coordination Disorders

<i>Objective: </i>To investigate the effects of brainstem auditory evoked potentials (BAEP) in treatment of developmental coordination disorder (DCD) in children. <i>Methods:</i> A total of 87 high-risk children who was examined by brainstem auditory evoked potentials (BAEP) in our hospital from August 2017 to December 2018 were enrolled in the study. According to Peabody motor development scale, these patients were divided into developmental coordination disorder (DCD) group (n=54) and non-developmental coordination disorder (non-DCD) group (n=33). After 3-month comprehensive rehabilitation treatment, the latency and changes of BAEP were observed and compared between the two groups. <i>Results: </i>As compared with brainstem auditory evoked potentials (BAEP) in non-developmental coordination disorder (non-DCD) group, the III, V and I ~ III wave latencies in developmental coordination disorder (DCD) group were significantly prolonged (P<0.05). After comprehensive rehabilitation treatment, the latency of each wave of BAEP in developmental coordination disorder (DCD) group was significantly shortened (P<0.01), as compared with that before treatment and that in non-developmental coordination disorder (non-DCD) group (P>0.05).<i> Conclusion:</i> Brainstem auditory evoked potentials (BAEP) can comprehensively, objectively and sensitively reflect the conduction function of central nervous system in children with developmental coordination disorder (DCD), which has important clinical application value in the evaluation of early rehabilitation effects.

Change of brainstem auditory-evoked potential in vertebrobasilar transient ischemic attack patients

Background: Transient ischemic attack describes the symptoms of the nervous system which occurs due to insufficient circulation that lasts for &lt;24 h. Its clinical manifestations tend to disappear quickly and it is also considered as an indicator of stroke. Brainstem auditory-evoked potentials are responses of the brainstem by auditory stimulation. Vertebrobasilar (VB) transient ischemia can cause brainstem ischemia which can induce BAEP changes. Hence, it becomes necessary to evaluate the electrophysiological changes in VB transient ischemic attack (VBTIA) patients so that early detection of neuronal changes and prevention of full-blown stroke. Aims and Objectives: The aim of this study was to compare the changes in brainstem auditory-evoked potential in VB TIA patients with normal subject. Materials and Methods: Auditory-evoked potential was recorded in 40 patients with VBTIA and 40 normal control groups. This study was conducted at the Research Laboratory, Department of Physiology, Thanjavur Medical College, Thanjavur. Results: The absolute latency of wave V was prolonged and a reduction in amplitude of wave V was observed in patients with VBTIA and it was found to be statistically significant. Conclusion: This study is very much useful to identify the early detection of the progression of stroke in VB TIA patients. Further studies are required to evaluate the correlation between the electrophysiological parameters and progression into stroke so that preventive measures can be used to prevent early involvement of Stroke.

Visual and Brainstem Auditory-evoked Potentials Correlate with Specific Motor and Non-motor Symptoms in Parkinson's Disease

Parkinson’s disease (PD) is a common and complex neurodegenerative disease characterized by progressive motor and non-motor symptoms. The current study investigated the dysfunction of brain hemispheres and brainstem of PD patients and its relation to motor and non-motor symptoms using brainstem auditory evoked potentials (BAEP) and pattern reversal visual evoked potentials (p-VEP). We hypothesized that some motor and non-motor symptoms of PD due to specific dysfunctions of brainstem and brain hemispheres could be related to changes in p-VEP and BAEP. Accordingly, the aim of this study was to explore the abnormalities of BAEPs and p-VEPs in patients with PD and its correlation to the motor and non-motor symptoms of PD. Seventy-six nondemented PD patients took part in the p-VEP evaluations and 66 nondemented PD patients were included in BAEP evaluation. In order to compare the p-VEP performance of PD group, we included a control group comprising 32 age-matched participants. A BAEP substudy involved 29 age-matched healthy controls. All patients underwent a comprehensive motor and non-motor neuropsychological assessment. We found significant changes in all tested parameters of p-VEPs in PD patients compared to control subjects. In addition, these lower scores in p-VEP correlate with the results of some tests for cognition related to frontal-striatal dysfunction and contralateral rigidity, but not with the results of overall motor evaluation or other non-motor symptoms studied. In BAEP, PD patients have a significant prolongation of III and V wave latencies compared to controls. In addition, when examining the possible associations of BAEP with other non-motor manifestations of the disease, such association was observed only by the apathy scale. In conclusion, the current study confirms the visual and auditory abnormalities among PD patients thatreflect brain hemispheres and brainstem pathological changes. It also correlates these abnormalities to some motor and non-motor features of the disease, providing a localizing tool for associated brain hemispheres and brainstem dysfunctions. Furthermore, abnormal visual evoked potentials are associated with motor and non-motor symptoms due to the basal ganglia dysfunction. In contrast, abnormal auditory evoked potentials are connected with apathy, which is considered to be related with brainstem raphe nuclei dysfunction.

Auditory evoked potentials in children and adolescents with multiple sclerosis and neuromyelitis optica spectrum disorders

BackgroundIn children, an acute demyelinating disease may evolve as a multiphasic disease with multiple relapses, such as multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD). The Brainstem Auditory Evoked Potentials (BAEP) and Long-Latency Auditory Evoked Potentials (LLAEP) contribute to the identification of either retrocochlear changes or other central auditory nervous system (CANS) changes. ObjectivesTo characterize BAEP and LLAEP in children and adolescents with MS and NMOSD and verify the diagnostic values of these potentials in each of the demyelinating diseases. MethodsThe 40 participants were divided into two study groups (SG1 – MS, SG2 – NMOSD) and two comparison groups (CG1 and CG2), matched for age (9 years–17 years and 11 months) and sex. Electrophysiological hearing assessment was performed with BAEP and LLAEP. ResultsWhen SG1 and SG2 were compared with CG1 and CG2 regarding BAEP and LLAEP, both SG1 and SG2 presented a higher occurrence of changes. Also, individuals with MS had higher occurrences of BAEP changes, whereas individuals with NMOSD had a higher occurrence of LLAEP changes. ConclusionsBAEP and LLAEP in children and adolescents with MS or NMOSD showed higher latencies and lower amplitudes of some components when these individuals were compared with their peers. These procedures were highly accurate to identify demyelinating diseases. BAEP results were more abnormal in individuals with MS, while LLAEP was so with NMOSD. These findings indicate that the auditory evoked potentials are important instruments for the differential diagnosis of MS and NMOSD, and valuable to monitor disease evolution.

Clinical characteristics of patients with young-onset hemifacial spasm: a retrospective analysis of 151 cases

Objective The average age of hemifacial spasm (HFS) onset is mostly between the fifth and sixth decades of life, with a relatively low incidence in younger age groups. The objective of this study was to analyze the characteristics and clinical outcomes of young-onset hemifacial spasm (YOHFS). Methods Between April 1997 and March 2021, 151 HFS patients aged 30 years or younger at the time of microvascular decompression (MVD) were selected. We analyzed their epidemiological characteristics, intraoperative findings, improvements, and postoperative complications by reviewing medical records. Results This study included 151 patients who underwent MVD. The average age of the patients was 26 years. The mean symptom duration was 36.5 months. The male-to-female sex ratio was 1:1.5. The most common offending vessel was the anterior inferior cerebellar artery, and the most common compression type was the arachnoid type. Improvements in spasm after MVD were seen in 96.7% of patients. No permanent facial palsy was noted after MVD. Changes in brainstem auditory-evoked potentials were recorded in 11 patients; however, no permanent hearing loss was observed. Conclusion The characteristics and clinical outcomes of YOHFS in this study were similar to those of patients with HFS in the general population. Based on the clinical outcomes, MVD for YOHFS is effective and safe. Therefore, MVD should be considered in patients with YOHFS. KEY WORDS: Hemifacial spasm, Microvascular decompression surgery, Prevalence

Role of Intraoperative Neurophysiologic Monitoring in Internal Carotid Artery Injury During Endoscopic Endonasal Skull Base Surgery

In the present study, we investigated the role of intraoperative neuromonitoring (IONM) in internal carotid artery (ICA) injury during endoscopic endonasal skull base surgery (EESBS). The study group included all 13 patients who had experienced an ICA injury during EESBS with IONM from 2004 to 2017. The medical records were reviewed for the perioperative data. The IONM reports were reviewed to evaluate the baseline somatosensory evoked potentials (SSEP), electroencephalography (EEG), and brainstem auditory evoked potentials (BAEP) and their significant changes related to ICA injury and/or the subsequent surgical/endovascular interventions. All 13 patients had undergone SSEP and 7 patients had BAEP monitoring during surgery. EEG was added during emergent angiography following the surgery for 5 patients. Two patients showed significant SSEP changes, and one showed significant SSEP and EEG changes, indicating cerebral hypoperfusion. Of these 3 patients, patient 1 had experienced irreversible SSEP loss with postoperative stroke. Patients 2 and 3 had SSEP and/or EEG changes that had recovered to baseline after interventions without postoperative deficits. Despite ICA injury, 10 patients showed no significant SSEP and/or EEG changes, and all 7 patients with BAEP monitoring showed no significant BAEP changes, indicating adequate cerebral and brainstem perfusion, respectively. The injured ICA was sacrificed in 4 patients, of whom 3 showed stable SSEP and 1 had experienced irreversible SSEP loss. IONM correlated with the postoperative neurologic examination findings in all cases, adequately predicting the neurologic outcomes after ICA injury. SSEP and EEG monitoring can accurately detect cerebral hypoperfusion and provide real-time feedback during surgery. SSEP and EEG changes predicted forneurologic outcomes and guide surgical decisions regarding the preservation or sacrifice of the ICA. Comprehensive multimodality monitoring according to the surgical risks can serve to detect and guide the management of ICA injury in EESBS.

A prewarning sign for hearing loss by brainstem auditory evoked potentials during microvascular decompression surgery for hemifacial spasm

ObjectiveWe aimed to define the prewarning sign of brainstem auditory evoked potentials (BAEPs) associated with cerebellar retraction (CR) during microvascular decompression surgery for hemifacial spasm. MethodsA total of 241 patients with a latency prolongation of 1 ms or an amplitude decrement of 50% of wave V were analyzed. According to BAEPs before significant changes during CR, patients were classified into Groups A (latency prolongation of wave I [≥0.5 ms] without prolongation of the I–III interpeak interval [<0.5 ms]) and B (no latency prolongation of wave I [<0.5 ms] with prolongation of the I–III interpeak interval [≥0.5 ms]). BAEPs and postoperative hearing loss (HL) were compared between the two groups. ResultsGroup B comprised 160 (66.4%) patients. With maximal changes in wave V, latency prolongation (≥1 ms) with amplitude decrement (≥50%) was more common in Group B (p < 0.018). At the end of the operation, wave V loss was observed in 11 patients, including 10 patients from Group B. Five patients developed postoperative HL; all were from Group B. ConclusionsLatency prolongation of wave III during CR was associated with serious BAEPs changes and postoperative HL. SignificanceLatency prolongation of wave III is a significant prewarning sign.

Predictive values of maximum changes of brainstem auditory evoked potentials during microvascular decompression for hemifacial spasm.

Brainstem auditory evoked potentials (BAEPs) have been widely monitored to prevent hearing loss (HL) during microvascular decompression (MVD) for hemifacial spasm (HFS); however, their predictive value is still unclear. The aim of this study is to investigate the predictive values of the maximum changes in BAEPs and define the best warning indicator and a cutoff value (CV) during HFS-MVD. The clinical data of 93 HFS-MVD patients were retrospectively analysed. The maximum change rates of the latency and amplitude of waves I, III, and V and the interpeak latencies (IPLs) I-III, I-V, and III-V, when BAEPs change most during MVD, were defined. Pure tone audiometry was performed to evaluate hearing loss (HL). Logistic regression, propensity score, receiver operating curve (ROC), and area under the curve (AUC) were used to identify the predictive value of relevant indexes and to determine the CV (with the largest Youden index) of the best index at different levels of HL. The AUCs of BAEPs for predicting HL were 0.98, 0.92, and 0.84 for 50dB, 30dB, and 10dB, respectively. The amplitude of wave V (AwV) was the best single predictive index at all three HL levels. The CV of AwV was 55% (50dB), 46% (30dB), and 34% (10dB). At 50dB HL, the predictive value of IPLs I-V (AUC 0.89 with CV 0.6ms) was better than that of LwV (AUC 0.82 with CV 1ms). BAEPs can predict HL well. AwV is the best single predictive index of all BAEPs. The reduction of AwV by 34% (watching), 46% (reporting), and 55% (warning) can be used as a sliding-scale warning sign. In addition, IPLs I-V (> 0.6ms) and LwV (> 1ms) should also be observed and reported during MVD.

Intraoperative neurophysiological monitoring in paediatric Chiari surgery-help or hindrance?

The role of intraoperative neurophysiological monitoring (IONM) during surgery for Chiari I malformation has not been fully elucidated. Questions remain regarding its utility as an adjunct to foramen magnum decompression surgery, specifically, does IONM improve the safety profile of foramen magnum decompression surgery and can IONM parameters help in intraoperative surgical decision-making. This study aimed to describe a single institution experience of IOM during paediatric Chiari I surgery. The methodology comprised a retrospective review of prospectively collected electronic neurosurgical departmental operative database. Inclusion criteria were children under 16years of age who had undergone foramen magnum decompression for Chiari I malformation with IONM. In addition to basic demographic data, details pertaining to presenting features and post-operative outcomes were obtained. These included primary symptoms of Chiari I malformation and indications for surgery. MRI findings, including the presence of syringomyelia on pre-and post-operative imaging, were reviewed. Details of the surgical technique for each patient were recorded. Only patients with either serial brainstem auditory evoked potential (BAEP) and/or upper limb somatosensory evoked potential (SSEP) recordings were included. Two time points were used for the purposes of analysing IONM data; initial baseline before skin incision and final at the time of skin closure. Thirty-seven children underwent foramen magnum decompression (FMD) with IONM. Mean age was 10.5years (range 1-16years) with a male:female ratio 13:24. The commonest clinical features on presentation included headaches (15) and scoliosis (13). Twenty-four patients had evidence of associated syringomyelia (24/37 = 64.9%). A reduction in the SSEP latency was observed in all patients. SSEP amplitude was more variable, with a decrease seen in 18 patients and an increase observed in 12 patients. BAEP recordings decreased in 13 patients and increased in 4 patients. There were no adverse neurological events following surgery; the primary symptom was resolved or improved in all patients at 3-month follow-up. Resolution or improvement in syringomyelia was observed in 19/24 cases. Our data shows that FMD for Chiari malformation (CM) is associated with changes in SSEPs and BAEPs. However, we did not identify a definite link between clinical outcomes and IONM, nor did syrinx outcome correlate with IONM. There may be a role for IONM in CM surgery but more robust data with better-defined parameters are required to further understand the impact of IONM in CM surgery.

Gonadal steroids and auditory evoked responses during menstrual cycle

Introduction: Brainstem Auditory Evoked Potentials (BAEP) have been subject to effect by many physiological restrictions. The gonadal steroids may be one of them, but few electrophysiological studies have documented any evidence. This study was carried out to record the auditory evoked response in females of reproductive age group in different phases of the menstrual cycle. Materials and Methods: This was an observational cross sectional study. The BAEP were recorded in 50 subjects (age 17-37 years, no h/o hormonal therapy) during three different phases of the same menstrual cycle. The peak latencies of the waves, I, II, III, IV and V, IPL I-III, I-V and III-V and the amplitude ratio, V/I were recorded and statistically analyzed. Results: A statistically significant increase in the latencies of the waves, I-V in the mid cycle coinciding with high estrogen level was observed. A statistically significant decrease in the mid-luteal phase was observed which corresponds to high progesterone levels. IPL did not show any significant change in the said phases. Similarly, no significant changes in the menstrual phase was seen for all variables. Conclusion: The results point out the BAEP changes in the mid follicular and the mid luteal phases of the menstrual cycle suggestive of effects of oestrogen and progesterone. Keywords: Menstrual cycle, Evoked Potential, Estrogen, Progesterone.

Delayed hearing loss after microvascular decompression for hemifacial spasm.

This study aimed to analyze cases of delayed hearing loss after microvascular decompression (MVD) for hemifacial spasm and identify the characteristic features of these patients. We retrospectively reviewed the medical records of 3462 patients who underwent MVD for hemifacial spasm between January 1998 and August 2017. Among these, there were 5 cases in which hearing was normal immediately postoperatively but delayed hearing loss occurred. None of the 5 patients reported any hearing disturbance immediately after the operation. However, they developed hearing problems suddenly after some time (median, 22days; range 10-45days). On examination, sensorineural hearing loss was confirmed. High-dose corticosteroid treatment was prescribed. Preoperative hearing levels were restored after several months (median duration from the time of the operation, 45days; range 22-118days). Interestingly, the inter-peak latency of waves I-III in the brainstem auditory evoked potential (BAEP) was prolonged during the surgery, but recovered within a short time. Delayed hearing loss may occur after MVD for HFS. Prolongation of the inter-peak latency of waves I-III seems to be associated with the occurrence of delayed hearing loss. It is possible that BAEP changes may predict delayed hearing loss, but confirmatory evidence is not available as yet. Analysis of more cases is necessary to determine the utility of BAEP monitoring to predict delayed hearing loss after MVD and to identify its exact cause.

Influence of malnutrition on the development of the central nervous system of malnourished children

Introduction: Protein-caloric malnutrition is a public health concern in certain areas of the Brazil. It can affect growth, the auditory nervous system development and, consequently, the cognition. This study compared the Brainstem Auditory Evoked Potential (BAEP) between malnourished and eutrophic children.Methods: A total of 111 children, aged 0–60 months, were examined: 57 were malnourished, according to the World Health Organization criteria, and 54 were normo-nourished. All the subjects underwent otorhinolaryngological evaluations and had acoustic immittance and transient evoked otoacoustic emissions within the normal range. The BAEP responses to click and tone burst stimuli were recorded at intensities of 80, 60, 40, and 30 dBNA.Results: We observed that latencies of I, III, and V waves and interpeaks III–V at 80 dBNA with click stimuli were significantly higher in all malnourished children when compared to those in the eutrophic children, as was the I–V interval in the 0- to 24-month group. The V-wave latencies at those intensities were also significantly higher in malnourished children.Conclusions: Malnourished children presented changes in BAEP characterized by delayed wave latency and interpeak intervals when compared to eutrophic children, suggesting alterations in both peripheral and central auditory pathways development and maturation.

The critical warning sign of real-time brainstem auditory evoked potentials during microvascular decompression for hemifacial spasm

ObjectiveThe aim of this study was to define the critical warning sign of real-time brainstem auditory evoked potential (BAEP) for predicting hearing loss (HL) after microvascular decompression (MVD) for hemifacial spasm (HFS). MethodsNine hundred and thirty-two patients with HFS who underwent MVD with intraoperative monitoring (IOM) of BAEP were analyzed. We used a 43.9 Hz/s stimulation rate and 400 averaging trials to obtain BAEP. To evaluate HL, pure-tone audiometry and speech discrimination scoring were performed before and one week after surgery. We analyzed the incidence for postoperative HL according to BAEP changes and calculated the diagnostic accuracy of significant warning criteria. ResultsOnly 11 (1.2%) patients experienced postoperative HL. The group showing permanent loss of wave V showed the largest percentage of postoperative HL (p < 0.001). No patient who experienced only latency prolongation (≥1 ms) had postoperative HL. Loss of wave V and latency prolongation (≥1 ms) with amplitude decrement (≥50%) were highly associated with postoperative HL. ConclusionsLoss of wave V and latency prolongation of 1 ms with amplitude decrement ≥50% were the critical warning signs of BAEP for predicting postoperative HL. SignificanceThese findings elucidate the critical warning sign of real-time BAEP.

Electrophysiology of Cranial Nerve Testing: Auditory Nerve.

The electrocochleogram and brainstem auditory evoked potentials (BAEPs) are electrophysiologic signals used to assess the auditory nerve. The electrocohleogram includes the cochlear microphonic, the cochlear summating potential, and the eighth nerve compound action potential. It is used predominantly for hearing assessment and for diagnosis of Ménière disease and auditory neuropathy. Brainstem auditory evoked potentials are used for hearing assessment, diagnosis of dysfunction within the cochlea, the auditory nerve, and the brainstem auditory pathways up to the level of the mesencephalon, and intraoperative monitoring of these structures. The earliest BAEP component, wave I, and the eighth nerve compound action potential reflect the same process-the initial depolarization in the distal auditory nerve. Brainstem auditory evoked potential wave II receives contributions from the region of the cochlear nucleus and from the second depolarization in the distal auditory nerve. Wave III and later components are entirely generated rostral to the auditory nerve. Interpretation of BAEP studies is based on waves I, III, and V; auditory nerve dysfunction is manifested as prolongation of the I-III interpeak interval or absence of waves III and V. Eighth nerve tumors can cause a variety of BAEP abnormalities depending on which structures they affect. Adverse intraoperative BAEP changes can have many etiologies, including direct mechanical or thermal injury of tissue, ischemia (including cochlear ischemia or infarction due to compromise of the internal auditory artery), eighth nerve stretch, systemic or localized hypothermia, and artifactual BAEP changes due to technical factors.

The Incidence of Early Postoperative Conductive Hearing Loss after Microvascular Decompression of Hemifacial Spasm.

Objectives To evaluate the incidence and discuss the pathogenesis of early postoperative conductive hearing loss (CHL) after microvascular decompression (MVD) for hemifacial spasm (HFS). Design Pre- and postoperative audiogram data and brainstem auditory evoked potentials (BAEPs) from patients who had underwent MVD for HFS were analyzed. Setting The study was conducted at the University of Pittsburgh Medical Center. Participants MVD for HFS patients who had pre- and postoperative audiogram data, BAEP data, and normal structure of the external and middle ear were included in the study. Main Outcome Measures CHL was diagnosed if there was an air-bone gap in pure tone audiometry of at least 10 dB at 0.5, 1, 2, or 4 kHz. Results The incidence of early postoperative CHL in the ipsilateral ear was 18.7% postoperatively. No CHL was observed in the contralateral side. No significant relationship between CHL and intraoperative BAEP changes was found. Demographic parameters were not significantly different between groups with and without CHL. Conclusions Early postoperative CHL is a significant complication after MVD. Fluid entering the mastoid air cells and/or bone-dust deposition during craniotomy may result in CHL. Long-term audiograms will be needed to evaluate the risk factors that lead to permanent CHL.

1-A-D-21. Changes of brainstem auditory evoked potentials after craniotomy and CSF drainage: Analysis of 344 consecutive patients during microvascular decompression

During microvascular decompression (MVD) surgery for hemifacial spasm and trigeminal neuralgia, slight changes of brainstem auditory evoked potentials (BAEP) can be observed without manipulation around the cochlear nerve. This study is aimed to examine influence of general anesthesia and cerebral spinal fluid (CSF) drainage on the BAEP. We included 344 patients with normal auditory function who underwent MVD. The BAEP data were compared at three points: (1) within a week before MVD, (2) just after induction of anesthesia, (3) after CSF drainage from cerebellar medullary cistern. The effects of anesthetic agents, age and previous surgery were also analyzed. After induction of anesthesia and CSF drainage, the latencies of wave V delayed for 0.318 ms and 0.206 ms on the average. The amplitudes of wave V increased approximately for 10% after CSF drainage. Sevoflurane prolonged latencies longer than propofol. In the elderly patients (>59 year-old), the latency of wave I delayed significantly longer than in younger patients. Previous surgery did not affect the BAEP changes. These findings indicate that the latencies of BEAP can be prolonged slightly without nerve injury, presumably due to local hypothermia, dryness and stretch of the nerves caused by anesthesia, craniotomy and CSF drainage during neurosurgery.

Value of multimodality monitoring using brainstem auditory evoked potentials and somatosensory evoked potentials in endoscopic endonasal surgery

Objectives: To evaluate the value of intraoperative neurophysiological monitoring (IONM) using brainstem auditory evoked potential (BAEP) and somatosensory evoked potential (SSEP) monitoring to predict and/or prevent postoperative neurological deficits during endoscopic endonasal surgery (EES).Methods: We retrospectively identified 138 consecutive patients who had BAEP monitoring in addition to SSEP monitoring during EES at our institution. We reviewed the postoperative clinical outcomes and neurophysiological changes independently.Results: The total of number of patients with any IONM changes was 10. The incidence of BAEP changes was 3·62%. The incidence of SSEP changes was 3·62% as well. One patient had changes in both BAEPs and SSEPs. Majority of the changes were observed during changes in mean arterial pressure (MAP) without any postoperative neurological deficits. There were two postoperative neurological deficits.Discussion: BAEPs and SSEPs provide unique information about integrity of brainstem function during EES procedures involving tumors in the and around clival region. We advocate a comprehensive multimodality approach to IONM during EESs including BAEPs and SSEPs depending on the location of the neural structures at risk.