Auditory temporal processing in patients with temporal lobe epilepsy

Objective measures of auditory temporal resolution with ABR

OBJECTIVE

To develop a reliable objective method to measure temporal resolution thresholds using Auditory Brainstem Response (ABR) with statistical response detection methods.

DESIGN

The ABR paradigms "Two Clicks (2C)" and "Temporal Notched Noise with Click (TNNC)" were evaluated for measuring objective temporal resolution thresholds. Statistical methods were used for ABR detection. Test-retest reliability of both ABR paradigms was also assessed. For comparison, a Gaps in Noise test and psychometric TNNC paradigm measured behavioural thresholds from the same subjects.

STUDY SAMPLE

23 normal-hearing participants in the main study, and an additional 10 in the test-retest experiment, aged 20-35 years.

RESULTS

Objective temporal resolution thresholds averaged 4.04 ms for the 2C paradigm and 3.21 ms for the TNNC paradigm. Group-level data showed reduced ABR amplitude and detection as gap durations approached threshold, whilst individual ABR amplitudes fluctuated across gap durations. Behavioural thresholds averaged 1.49 and 2.22 ms. In the test-retest experiment, TNNC showed moderate repeatability, while 2C had slight, non-significant repeatability (measured by Cohen's Kappa).

CONCLUSIONS

While these objective approaches show promise for measuring temporal resolution at a group level, their application in individuals remains challenging due to high variability across subjects. The TNNC paradigm demonstrated better performance in terms of ABR repeatability.

Listening with one hemisphere: A review of auditory processing among individuals after hemispheric surgery

The human auditory system consists of both peripheral and central components, both of which play a role but contribute distinctly to overall auditory functioning and can be differentially impacted by pathophysiologic states. Hemispheric surgery (HS), a procedure used for the treatment of drug-resistant epilepsy, involves complete disconnection of the auditory cortex in the operative hemisphere, leaving hearing acuity (peripheral function) intact but having heavy implications for auditory processing (central function). The literature describing pre- and post-operative auditory processing abilities of individuals who have undergone HS is sparse, but the research available provides evidence that several central auditory processes including auditory spatial analysis and temporal processing may be impacted. Deficits noted in standardized testing within the clinical or research environment have concrete functional impacts that may be currently under-appreciated and could lead to under-utilization of appropriate therapeutic strategies and accommodations. This review describes the profile of central auditory processing abilities in patients who have undergone HS by synthesizing available literature and incorporating research in other clinical populations to help fill critical gaps in our understanding of how cerebral disconnection impacts the central auditory system.

Auditory processing in patients with temporal lobe epilepsy: A systematic review and meta-analysis

BACKGROUND

Hearing efficiency is known to influence and interact with communication and mental health. Hearing impairment may be hidden when co-occurring with neurological disorders.

PURPOSE

We performed a systematic review and meta-analysis in order to address the following questions: 1) which specific tools of auditory processing show clear deficits, separating Temporal Lobe Epilepsy (TLE) patients from normal controls,2) How well is TLE evaluated in terms of hearing and auditory processing?

METHODS

The study inclusion criteria were: 1) patients diagnosed with temporal lobe epilepsy, 2) presence of a normal control group, 3) auditory processing assessment using auditory stimuli with behavioral tests and/or P300 or Mitch Match Negativity (MMN) latency and/or amplitude, 4) publications written in English, 5) publication date after 2000. 132 articles were retrieved and based on PRISMA & PICO criteria 23 articles were analyzed.

RESULTS

Temporal resolution and processing as measured by the behavioral tests of Gaps-In-Noise (GIN) and Duration Pattern Test (DPT) document deficiencies in TLE patients and separate them from normal controls. Electrophysiology as measured by MMN & P300 shows statistically significant differences in TLE patients compared to controls with patients showing deficient auditory processing. A clear difference between studies with psychoacoustic assessment as opposed to electrophysiology ones may be due to lacking or incomplete evaluation of peripheral hearing by gold standard tools (76.9% in electrophysiology studies).

CONCLUSION

Auditory processing is deficient in patients with TLE. There is a clear need to evaluate hearing efficiency before proceeding to auditory processing evaluation with behavioral or electrophysiological tests.

80 Hz auditory steady state responses (ASSR) elicited by silent gaps embedded within a broadband noise

Introduction

Although auditory temporal processing plays an important role in speech comprehension, it cannot be measured by pure tone audiometry. Auditory temporal resolution is often assessed by behavioral gaps-in-noise test. To evaluate whether auditory temporal resolution could be objectively assessed, we measured the auditory steady state response (ASSR) elicited by silent gaps embedded within broadband noises at 80 Hz.

Methods

We prepared six sound types as test stimuli. One was a continuous broadband noise without a silent interval as a control stimulus and the others were broadband noises with 80 Hz silent intervals of 0.4, 0.8, 1.6, 3.1, and 6.3 ms.

Results

Significant ASSRs were recorded only when the gap length was longer than the behavioral thresholds and the ASSR amplitude increased as the gap length increased.

Conclusion

Eighty Hertz gap-evoked ASSR appears to reflect the neural activity related to the auditory gap processing and may be used as an objective measure of auditory temporal resolution in humans.

Effectiveness of the Auditory Temporal Ordering and Resolution Tests to Detect Central Auditory Processing Disorder in Adults With Evidence of Brain Pathology: A Systematic Review and Meta-Analysis

Background: Auditory temporal processing tests are key clinical measures in order to diagnose central auditory processing disorder (CAPD). Although these tests have been used for decades, there is no up-to-date evidence to determine the effectiveness of detecting the abnormalities in central auditory processing in adults while the available national CAPD guidelines predominantly address CAPD in the pediatric population.

Purpose: To determine the efficacy of the auditory temporal ordering tests [duration pattern test (DPT) and frequency pattern test (FPT)], and a temporal resolution test [gaps-in-noise (GIN) test] for detecting the central auditory processing abnormalities in adults with documented brain pathology.

Research Design: Systematic reviews and meta-analyses.

Study samples: Four databases, including PubMed, Web of Science, Embase, and Scopus, were systematically searched. The publications in the English language that recruited adults (above 16 years old) with pathologic brain conditions and described the diagnostic tests for auditory temporal processing were selected for review.

Data Collections and Analysis: All data were systematically evaluated, extracted, categorized, and summarized in tables. The meta-analysis was done in order to determine the effectiveness of the DPT, FPT, and GIN tests.

Results: The results showed significantly poorer performance of DPT and FPT, compared between participants with confirmed brain disease and normal controls, at the mean differences of percent correct −21.93 (95% CI, −26.58 to −17.29) and −31.37 (95% CI, −40.55 to −22.19), respectively. Subjects with brain pathology also performed poorer in GIN test at the mean difference of 3.19 milliseconds (95% CI, 2.51 to 3.87).

Conclusion: The results from the meta-analysis provide evidence that DPT, FPT, and GIN clinical measures are effective in the diagnosis of CAPD in adults with neurological disorders. Poor performance on these tests is significantly related to the confirmed brain pathology. However, different units in results presentation and variety of testing strategies are limitations for this meta-analysis. The standard pattern of result reporting and international protocols test strategies should be developed in order to conduct better meta-analyses with a larger collection of suitable studies and less heterogeneity.

Neuromagnetic oscillations in the human sensory systems: A mini review of our series and literature

Oscillatory neuronal (electrical) activity in defined frequency ranges supports synchronous interactions between anatomically distinct regions of the human brain during cognitive tasks. Here, the author reviews our previous studies that focused on the neuromagnetic oscillations in the sensory systems in response to the external stimuli in normal healthy subjects and neurological disorders. A magnetoencephalography was applied to evaluate the neuromagnetic oscillations in humans. We have demonstrated that the oscillatory gamma synchronization binds the primary and secondary somatosensory areas (S1 and S2) in humans. This functional coupling is modulated by aging. In people who stutter, functional and structural reorganization of the right auditory cortex appears to be a compensatory mechanism for impaired left auditory cortex function. This may be partly caused by increased right hemispheric local phase synchronization and increased inter-hemispheric phase synchronization. We have also found that the hippocampus modulates auditory processing differently under normal conditions and in epileptic patients with hippocampal sclerosis. This indicates that altered neural synchronization may provide useful information about possible functional deterioration in patients with unilateral mesial temporal lobe epilepsy. Finally, supraspinal (cortical) mechanism is responsible for pain perception and pain relief via neural oscillations. Together, neuronal synchronization plays an important role in distributed cortico-cortical processing.

Peripheral and central auditory function in adults with epilepsy and treated with carbamazepine

Purpose of the study:

Epilepsy is a chronic medical disease in one third of patients. Chronic epilepsy and its antiepileptic drugs (AEDs) therapy are commonly associated with comorbid adverse somatic conditions. This study aimed to evaluate auditory function in patients with idiopathic epilepsy and on treatment with carbamazepine (CBZ).

Methods:

This is a cross-sectional case-control study. It included 50 patients with idiopathic epilepsy (mean age = 34.56 ± 7.11 and duration of illness = 17.84 ± 7.21years) and 40 healthy subjects. Hearing was evaluated using pure tone audiometry and brainstem auditory evoked potentials (BAEPs) analyses.

Results:

Mild bilateral hearing impairment and abnormal acoustic reflex (but normal tympanometry) were reported in more than one third of patients. Compared to controls, BAEPs of patients had prolonged waves I, III, V latencies and I–III, III–V and I–V interpeak latencies (IPLs) particularly at high repetition frequencies. Significant correlations were identified between CBZ dose, serum level and duration of treatment with waves I, III and V and I–III, III–V and I–V latencies at high repetition frequencies.

Conclusions:

Long-term treatment with CBZ may result in delayed auditory conduction within the peripheral pathways and brainstem. This should be taken into account during drug selection and monitoring of patients with epilepsy.

Monaural 40-Hz auditory steady-state magnetic responses can be useful for identifying epileptic focus in mesial temporal lobe epilepsy

OBJECTIVE

Patients with mesial temporal lobe epilepsy (mTLE) often exhibit central auditory processing (CAP) dysfunction. Monaural 40-Hz auditory steady-state magnetic responses (ASSRs) were recorded to explore the pathophysiology of mTLE.

METHODS

Eighteen left mTLE patients, 11 right mTLE patients and 16 healthy controls (HCs) were examined. Monaural clicks were presented at a rate of 40 Hz. Phase-locking factor (PLF) and power values were analyzed within bilateral Heschl's gyri.

RESULTS

Monaural 40-Hz ASSR demonstrated temporal frequency dynamics in both PLF and power data. Symmetrical hemispheric contralaterality was revealed in HCs. However, predominant contralaterality was absent in mTLE patients. Specifically, right mTLE patients exhibited a lack of contralaterality in response to left ear but not right ear stimulation, and vice versa in left mTLE patients.

CONCLUSION

This is the first study to use monaural 40-Hz ASSR with unilateral mTLE patients to clarify the relationship between CAP and epileptic focus. CAP dysfunction was characterized by a lack of contralaterality corresponding to epileptic focus.

SIGNIFICANCE

Monaural 40-Hz ASSR can provide useful information for localizing epileptic focus in mTLE patients.

Altered neural synchronization to pure tone stimulation in patients with mesial temporal lobe epilepsy: An MEG study

OBJECTIVE

Our previous study of monaural auditory evoked magnetic fields (AEFs) demonstrated that hippocampal sclerosis significantly modulated auditory processing in patients with mesial temporal lobe epilepsy (mTLE). However, the small sample size (n = 17) and focus on the M100 response were insufficient to elucidate the lateralization of the epileptic focus. Therefore, we increased the number of patients with mTLE (n = 39) to examine whether neural synchronization induced by monaural pure tone stimulation provides useful diagnostic information about epileptic foci in patients with unilateral mTLE.

METHODS

Twenty-five patients with left mTLE, 14 patients with right mTLE, and 32 healthy controls (HCs) were recruited. Auditory stimuli of 500-Hz tone burst were monaurally presented to subjects. The AEF data were analyzed with source estimation of M100 responses in bilateral auditory cortices (ACs). Neural synchronization within ACs and between ACs was evaluated with phase-locking factor (PLF) and phase-locking value (PLV), respectively. Linear discriminant analysis was performed for diagnosis and lateralization of epileptic focus.

RESULTS

The M100 amplitude revealed that patients with right mTLE exhibited smaller M100 amplitude than patients with left mTLE and HCs. Interestingly, PLF was able to differentiate the groups with mTLE, with decreased PLFs in the alpha band observed in patients with right mTLE compared with those (PLFs) in patients with left mTLE. Right hemispheric predominance was confirmed in both HCs and patients with left mTLE while patients with right mTLE showed a lack of right hemispheric predominance. Functional connectivity between bilateral ACs (PLV) was reduced in both patients with right and left mTLE compared with that of HCs. The accuracy of diagnosis and lateralization was 80%-90%.

CONCLUSION

Auditory cortex subnormal function was more pronounced in patients with right mTLE compared with that in patients with left mTLE as well as HCs. Monaural AEFs can be used to reveal the pathophysiology of mTLE. Overall, our results indicate that altered neural synchronization may provide useful information about possible functional deterioration in patients with unilateral mTLE.

Is there auditory impairment in Parkinson's disease?

ABSTRACT Objective: to describe the audiological profile of a group of patients with Parkinson's disease and to investigate the association between hearing loss and the disease. Methods: 50 individuals with and 46 without Parkinson's disease underwent Pure Tone Audiometry, Otoacoustic Emissions by Distortion Product, and auditory processing tests. The results of the patients were compared to those obtained in individuals without the disease, according to clinical and biological variables. Results: in individuals with Parkinson's disease, 82% presented hearing loss, 53.5% alterations in Otoacoustic Emissions by Distortion Product, 78%, alterations in temporal processing, and 12%, changes in binaural integration. Individuals with the disease had a greater impairment in the recognition of duration patterns when compared to those without the disease, with a worse performance in men and in individuals aged between 42 and 65 years old and Hoehn and Yahr I and II stages. Conclusions: the profile found corresponds to descending sensorineural hearing loss and alteration in otoacoustic emissions, temporal ordering and noise gaps detection.Only losses in temporal order are associated with the disease, especially in men, individuals under the age of 65 and in the initial stage.

Non-linear ICA Analysis of Resting-State fMRI in Mild Cognitive Impairment

Compared to linear independent component analysis (ICA), non-linear ICA is more suitable for the decomposition of mixed components. Existing studies of functional magnetic resonance imaging (fMRI) data by using linear ICA assume that the brain's mixed signals, which are caused by the activity of brain, are formed through the linear combination of source signals. But the application of the non-linear combination of source signals is more suitable for the mixed signals of brain. For this reason, we investigated statistical differences in resting state networks (RSNs) on 32 healthy controls (HC) and 38 mild cognitive impairment (MCI) patients using post-nonlinear ICA. Post-nonlinear ICA is one of the non-linear ICA methods. Firstly, the fMRI data of all subjects was preprocessed. The second step was to extract independent components (ICs) of fMRI data of all subjects. In the third step, we calculated the correlation coefficient between ICs and RSN templates, and selected ICs of the largest spatial correlation coefficient. The ICs represent the corresponding RSNs. After finding out the eight RSNs of MCI group and HC group, one sample t-tests were performed. Finally, in order to compare the differences of RSNs between MCI and HC groups, the two-sample t-tests were carried out. We found that the functional connectivity (FC) of RSNs in MCI patients was abnormal. Compared with HC, MCI patients showed the increased and decreased FC in default mode network (DMN), central executive network (CEN), dorsal attention network (DAN), somato-motor network (SMN), visual network(VN), MCI patients displayed the specifically decreased FC in auditory network (AN), self-referential network (SRN). The FC of core network (CN) did not reveal significant group difference. The results indicate that the abnormal FC in RSNs is selective in MCI patients.

The auditory and vestibular toxicities induced by antiepileptic drugs

Epilepsy is a chronic medical disease in one third of patients and is associated with comorbid adverse somatic conditions due to epilepsy itself or its long-term treatment with antiepileptic drugs (AEDs). Data from experimental, cross-sectional and prospective studies have evidence for the deleterious effect of some AEDs on the auditory and vestibular systems. These abnormalities may be reversible or irreversible. Areas covered: This article review the evidence that long-term treatment with some antiepileptic drugs (AEDs) [e.g. carbamazepine, phenytoin, valproate, lamotrigine, gabapentin, vigabatrin and oxcarbazepine] (even in therapeutic drug doses) may result in tinnitus, phonophobia, sensorineural hearing loss, dizziness, ataxia, disequilibrium, imbalance, nystagmus, abnormalities in saccadic and pursuit eye movements and delayed conduction within the cochlea, auditory nerve and brainstem auditory pathways evidenced by abnormalities in Brainstem auditory evoked potentials and nystagmography recordings indicating auditory and central and/or peripheral vestibular dysfunctions. Expert opinion: Identification of monitoring of patients at high risk for developing audio-vestibular manifestations is necessary for appropriate preventive and therapeutic measures.