A Review of the Role of Auditory Evoked Potentials in Mild Traumatic Brain Injury Assessment

The role of focused attention in learning from early childhood to late adolescence: Implications of neonatal brainstem compromise following preterm birth

This comprehensive longitudinal study explored for the first time the interrelations between neonatal brainstem abnormalities, focused attention (FA), and learning-following a preterm cohort (N = 175; 46.3% female; predominantly White) from birth (2003-2006) to 17 years. The findings indicated that FA during early childhood was associated with language outcomes in toddlerhood (n = 131) and academic and attention self-report indices in late adolescence (n = 44). Pilot assessments indicated that FA at 17 years (n = 25) was also associated with concurrent academic and attention functioning. Structural equation modeling analyses revealed that neonatal brainstem functioning, manifested in auditory brainstem response patterns, was associated with early-life FA competence, which affected learning development. Implications underscore the essential role of early brainstem function and FA in shaping childhood learning trajectories.

Regression-Based Classification of the Middle-Latency Auditory-Evoked Potentials in Vestibular Migraine and Concussion Patients with Dizziness

BACKGROUND/OBJECTIVES

The auditory middle-latency responses (AMLRs) assess central sensory processing beyond the brainstem and serve as a measure of sensory gating. They have clinical relevance in the diagnosis of neurological conditions. In this study, magnitude and habituation of the AMLRs were tested for sensitivity and specificity in classifying dizzy patients with vestibular migraine (VM) and post-concussive syndrome.

METHODS

Twenty-three healthy individuals, 12 concussion and 26 VM patients were recruited. AMLR were recorded performing five blocks of 200 binaural click-stimulations at 60 dB sensation level with a repetition rate of 6.1 Hz. Reduction in P0, Na and Pa magnitudes between blocks was measured. Group classifications were performed through logistic and multiple regression.

RESULTS

Among healthy subjects, a consistent P0 and Na habituation can be observed. Concussed subjects show control-like Na habituation, despite a lower magnitude, while P0 habituation was negligible. VM patients showed poor habituation for all waves. Regression analyses suggest that P0 and Na better distinguish healthy subjects from neurological patients, whereas Pa best distinguishes concussion from VM patients.

CONCLUSIONS

The results support that AMLR habituation can contribute to unraveling different mechanisms of dizziness due to concussion compared to VM, providing insights that can complement routine diagnostic assessments.

Contralateral Hearing Loss in Temporal Bone Fractures: A Potential Association with Combined Intracranial Injury

Temporal bone (TB) fractures are frequently accompanied by intracranial injury. This study aimed to analyze combined intracranial injuries in relation to functional changes in the inner ear, including those of the contralateral ear, in patients with TB fractures. Ninety-four patients (mean age: 35.6 ± 18.7 years, M : F=67 : 27) diagnosed with unilateral TB fracture were included. Bone conduction (BC) threshold, word recognition score (WRS), and changes in vestibular function were compared based on intracranial injuries, focusing on the contralateral side. Various types of intracranial injuries were observed (67.9%). Among these, a significant association between traumatic brain injury (TBI) and otic capsule-violating fractures was noted. The BC threshold on the fractured side significantly deteriorated in patients with TBI. Additionally, a significantly worse BC threshold was confirmed on the contralateral side in patients with TBI, intracranial hemorrhage (ICH), and contrecoup injury. The follow-up BC threshold did not improve or differ, regardless of high-dose steroid administration. The initial WRS and canal paresis in the bithermal caloric test were not significantly different in the presence of each intracranial injury. Concurrent fluctuations in the pressure of the cerebrospinal fluid space and perilymphatic space were speculated to be the potential underlying mechanisms. A significantly worse BC threshold was confirmed on the contralateral side of patients with TBI, contrecoup injury, ICH, and on fracture sides of patients with TBI.

Multi-channel and multi-harmonic analysis of Auditory Steady-State Response detection

The Auditory Steady-State Response (ASSR) is a type of auditory evoked potential (AEP) generated in the auditory system that can be automatically detected by means of objective response detectors (ORDs). ASSRs are usually registered on the scalp using electroencephalography (EEG). ORD are univariate techniques, i.e. only uses one data channel. However, techniques involving more than one channel - multi-channel objective response detectors (MORDs) - have been showing higher detection rate (DR) when compared to ORD techniques. When ASSR is evoked by amplitude stimuli, the responses could be detected by analyzing the modulation frequencies and their harmonics. Despite this, ORD techniques are traditionally applied only in its first harmonic. This approach is known as one-sample test. The q-sample tests, however, considers harmonics beyond the first. Thus, this work proposes and evaluates the use of q-sample tests using a combination of multiple EEG channels and multiple harmonics of the stimulation frequencies and compare them with traditional one-sample tests. The database used consists of EEG channels from 24 volunteers with normal auditory threshold collected following a binaural stimulation protocol by amplitude modulated (AM) tone with modulating frequencies near 80 Hz. The best q-sample MORD result showed an increase in DR of 45.25% when compared with the best one-sample ORD test. Thus, it is recommended to use multiple channels and multiple harmonics, whenever available.

Regional variations distinguish auditory from visual evoked potentials in healthy 4 week old piglets

Objective.Evoked potentials (EP), measured using electroencephalographic (EEG) recordings provide an opportunity to monitor cognitive dysfunctions after neurological diseases or traumatic brain injury (TBI). The 4 week old piglet is an established model of paediatric TBI; therefore, healthy piglets were studied to establish feasibility of obtaining responses to auditory and visual stimuli. A secondary aim was to input the EEG data into a piglet computational model to localize the brain sources related to processing. We tested the hypotheses: (1) visual, auditory-standard, and auditory-target stimuli elicit responses, (2) there is an effect of stimulus type, day tested, and electrode region on EPs from EEG, (3) there is an effect of stimulus type, day tested, and brain region on localized sources from a computational model.Approach.Eleven 4 week old female piglets were fitted with a 32-electrode net and presented with a simple white light stimulus and an auditory oddball click train (70 standard; 30 target tones).Main results.N1 andP2 amplitudes were consistently observed for all stimulus types. Significant interaction effects between brain region and stimulus for EP and current density demonstrate that cognitive responses are specific to each modality with auditory localizing to the temporal region and visual to the occipital regions. There was a day effect where larger responses were found on the first day than day 2 and 3 and may be due to the novelty of the stimulus on the first day. Visual stimuli had largerP1 amplitudes and earlier latencies (P1,N1) than auditory which coincides with current density results at 50 ms where larger activations were observed for visual. At 85 ms, auditory had significantly larger current densities coincident with larger and longerN1 amplitudes and latencies than visual.Significance.Auditory and visual processing were successfully and consistently obtained in a porcine model and can be evaluated as a diagnostic assessment for TBI.

A comparison between tau and amyloid-β cerebrospinal fluid biomarkers in chronic traumatic encephalopathy and Alzheimer disease

BACKGROUND

Cerebrospinal fluid (CSF) tau and beta-amyloid levels in chronic traumatic encephalopathy (CTE), a disease which can be clinically indistinguishable from Alzheimer's disease (AD), are largely unknown. We examined postmortem CSF analytes among participants with autopsy confirmed CTE and AD.

METHODS

In this cross-sectional study 192 participants from the Boston University AD Research Center, VA-BU-CLF Center, and Framingham Heart Study (FHS) had post-mortem CSF collected at autopsy. Participants were divided into pathological groups based on AD and CTE criteria, with 61 CTE participants (18 low, 43 high stage), 79 AD participants (23 low, 56 intermediate to high), 11 participants with CTE combined with AD, and 41 participants lacking both CTE and AD neuropathology. The Meso Scale Discovery immunoassay system was utilized to measure amyloid-beta (Aβ1-40, Aβ1-42), total tau (t-tau), and phosphorylated tau (p-tau181 and p-tau231). CSF analytes were then compared across the pathological groups: no CTE/no AD (control), Low CTE, Low AD, High CTE, Intermediate/High AD, and AD+CTE.

RESULTS

Among the Low disease state groups, the Low CTE group had significantly higher levels of p-tau231 versus the control group and compared to the Low AD group. The Low CTE group was also found to have significantly lower levels of Aβ1-42 compared to the control group. The high CTE group had higher levels of p-tau231 and lower levels of Aβ1-42 compared to Intermediate/High AD group.

CONCLUSIONS

Importantly, p-tau231 and Aβ1-42 were predictors of diagnosis of CTE vs. control and CTE vs. AD. Increased CSF p-tau231 is a promising potentially sensitive biomarker of CTE, and CSF Aβ1-42 needs further investigation in CTE.

The role of AT-SLP collaborations in return to academics following mTBI: A scoping review

Return-to-academics (RTA) for student-athletes with mild traumatic brain injury (mTBI) is crucial, but relatively understudied compared to return-to-play (RTP). The transient and unpredictable nature of symptoms surrounding mTBI often results in underreporting of neurocognitive symptoms, leading to a greater susceptibility for repeated TBIs, as well as posing impediments to the process of RTA. Athletic Trainers (ATs) and Speech-Language Pathologists (SLPs) are in a unique position to help student-athletes achieve a safe, timely, and effective RTA following mTBI. They typically work in middle/high schools and collegiate-level academic settings and often serve as members of concussion management teams. Compared to other allied health professions, ATs and SLPs are relatively new professions with evolving scopes of practice. Despite established guidelines and recommendations for their scope of practice in treating student-athletes with mTBI, there is a lacuna in research regarding their individual and collaborative roles in achieving RTA. The current scoping review was conducted with the main goal of exploring published literature pertaining to the roles of ATs and SLPs in achieving RTA for student-athletes with mTBI. Current implications, recommendations for integrating pre-service interprofessional education (IPE) experiences, and future directions for AT-SLP collaborations are discussed.

The role and use of event-related potentials in aphasia: A scoping review

Event-related potentials (ERPs) can provide important insights into underlying language processes in both unimpaired and neurologically impaired populations and may be particularly useful in aphasia. This scoping review was conducted to provide a comprehensive summary of how ERPs have been used with people with aphasia (PWA), with the goal of exploring the potential clinical application of ERPs in aphasia assessment and treatment. We identified 117 studies that met inclusionary criteria, reflecting six thematic domains of inquiry that relate to understanding both unimpaired and aphasic language processing and the use of ERPs with PWA. In these studies, a wide variety of ERP components were reported. Inconsistencies in reporting of participant characteristics and study protocols limit our ability to generalize beyond the individual studies and understand implications for clinical applicability. We discuss the potential roles of ERPs in aphasia management and make recommendations for further developing ERPs for clinical utility in PWA.

Head Injury Exposure in Veterans Presenting to Memory Disorders Clinic: An Observational Study of Clinical Characteristics and Relationship of Event-Related Potentials and Imaging Markers

Objective: Traumatic brain injury (TBI) and repetitive head impacts (RHI) related to blasts or contact sports are commonly reported among military service members. However, the clinical implications of remote TBI and RHI in veterans remains a challenge when evaluating older veterans at risk of neurodegenerative conditions including Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE). This study aimed to test the hypothesis that veterans in a memory disorders clinic with remote head injury would be more likely to have neurodegenerative clinical diagnoses, increased rates of amyloid PET positivity, higher prevalence of cavum septum pellucidi/vergae, and alterations in event-related potential (ERP) middle latency auditory evoked potentials (MLAEPs) and long latency ERP responses compared to those without head injuries. Methods: Older veterans aged 50-100 were recruited from a memory disorders clinic at VA Boston Healthcare system with a history of head injury (n = 72) and without head injury history (n = 52). Patients were classified as reporting prior head injury including TBI and/or RHI exposure based on self-report and chart review. Participants underwent MRI to determine presence/absence of cavum and an ERP auditory oddball protocol. Results: The head injury group was equally likely to have a positive amyloid PET compared to the non-head injury group. Additionally, the head injury group were less likely to have a diagnosis of a neurodegenerative condition than those without head injury. P200 target amplitude and MLAEP amplitudes for standard and target tones were decreased in the head injury group compared to the non-head injury group while P3b amplitude did not differ. Conclusions: Veterans with reported remote head injury evaluated in a memory disorders clinic were not more likely to have a neurodegenerative diagnosis or imaging markers of neurodegeneration than those without head injury. Decreased P200 target and MLAEP target and standard tone amplitudes in the head injury group may be relevant as potential diagnostic markers of remote head injury.

Target detection in healthy 4-week old piglets from a passive two-tone auditory oddball paradigm

BACKGROUND

Passive auditory oddball tests are effort independent assessments that evaluate auditory processing and are suitable for paediatric patient groups. Our goal was to develop a two-tone auditory oddball test protocol and use this clinical assessment in an immature large animal model. Event-related potentials captured middle latency P1, N1, and P2 responses in 4-week old (N = 16, female) piglets using a custom piglet 32- electrode array on 3 non-consecutive days. The effect of target tone frequency (250 Hz and 4000 Hz) on middle latency responses were tested in a subset of animals.

RESULTS

Results show that infrequent target tone pulses elicit greater N1 amplitudes than frequent standard tone pulses. There was no effect of day. Electrodes covering the front of the head tend to elicit greater waveform responses. P2 amplitudes increased for higher frequency target tones (4000 Hz) than the regular 1000 Hz target tones (p < 0.05).

CONCLUSIONS

Two-tone auditory oddball tests produced consistent responses day-to-day. This clinical assessment was successful in the immature large animal model.

The clinical utility of the cervical vestibular-evoked myogenic potential (cVEMP) in university-level athletes with concussion

INTRODUCTION

Concussion is defined as a mild traumatic brain injury that can occur in all sport activities. Cervical vestibular-evoked myogenic potentials (cVEMPs) are accepted to demonstrate the vestibulocollic reflex. MAIN: To evaluate subclinical cervical abnormalities in the vestibulospinal pathway in subjects with concussion history with and without related symptoms via evoked vestibular potential.

METHODS

Monaurally air conduction cVEMP (500 Hz tone bursts) at intensity of 100 dBnHL and 200 sweeps. All responses were replicated.

RESULTS

One hundred fifty-four participants were initially tested; however, three (03) participants did not produce usable data (no response) and were eliminated for the dataset cutoff values analysis, being considered just as abnormal response. One hundred fifty-one responses consisted of 45 non-athlete individuals without any history of a concussion or concussion symptoms (normative group), 45 athletes without any history of a concussion or concussion symptoms (control group), 33 athletes with a history of at least one concussion but no concussion symptoms related (history group), and 28 athletes with a history of at least one concussion and concussion symptoms (symptoms group). The history and symptoms groups had statistically higher latency scores than the control and the normative groups. The Index Ratio data and Threshold data did not produce a significant effect for four groups. But, a pattern of abnormal cVEMP was found when comparing those without a history of concussion (0% abnormal response) versus the history group (24%) and symptoms group (32.3%).

CONCLUSION

The study provides data which supports the positive impact of cVEMP when evaluating athletes and identifying concussion processes.

Towards detection of brain injury using multimodal non-invasive neuromonitoring in adults undergoing extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation (ECMO) is a form of cardiopulmonary bypass that provides life-saving support to critically ill patients whose illness is progressing despite maximal conventional support. Use in adults is expanding, however neurological injuries are common. Currently, the existing brain imaging tools are a snapshot in time and require high-risk patient transport. Here we assess the feasibility of measuring diffuse correlation spectroscopy, transcranial Doppler ultrasound, electroencephalography, and auditory brainstem responses at the bedside, and developing a cerebral autoregulation metric. We report preliminary results from two patients, demonstrating feasibility and laying the foundation for future studies monitoring neurological health during ECMO.

An Experimental Swallow Evoked Potential Protocol to Investigate the Neural Substrates of Swallowing

Advancement in dysphagia intervention is hindered by our lack of understanding of the neural mechanisms of swallowing in health and disease. Evoking and understanding neural activity in response to normal and disordered swallowing is essential to bridge this knowledge gap. Building on sensory evoked potential methodology, we developed a minimally invasive approach to generate swallow evoked potentials (SwEPs) in response to repetitive swallowing induced by citric acid stimulation of the oropharynx in lightly anesthetized healthy adult rats. The SwEP waveform consisted of 8 replicable peaks within 10 milliseconds immediately preceding the onset of electromyographic swallowing activity. Methodology refinement is underway with healthy rats to establish normative SwEP waveform morphology before proceeding to models of advanced aging and age-related neurodegenerative diseases. Ultimately, we envision that this experimental protocol may unmask the pathologic neural substrates contributing to dysphagia to accelerate the discovery of targeted therapeutics.