Assessment of visual and auditory evoked potentials in multiple sclerosis patients with and without fatigue

Auditory central pathways in children and adolescents with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is an inflammatory demyelinating disease. Auditory evoked potential studies have demonstrated conduction and neural processing deficits in adults with MS, but little is known about the electrophysiological responses in children and adolescents.

OBJECTIVE

to evaluate the central auditory pathway with brainstem auditory evoked potentials (BAEP) and long-latency auditory evoked potentials (LLAEP) in children and adolescents with MS.

METHODS

The study comprised 17 individuals with MS, of both sexes, aged 9 to 18 years, and 17 healthy volunteers, matched for age and sex. All individuals had normal hearing and no middle ear impairments. They were assessed with click-BAEP and LLAEP through oddball paradigm and tone-burst stimuli.

RESULTS

Abnormal responses were observed in 60% of electrophysiologic assessments of individuals with MS. In BAEP, 58.82% of MS patients had abnormal responses, with longer wave V latency and therefore longer III-V and I-V interpeak latencies than healthy volunteers. In LLAEP, 52.94% of MS patients had abnormal responses. Although statistical differences were found only in P2-N2 amplitude, MS patients had longer latencies and smaller amplitudes than healthy volunteers in all components.

CONCLUSION

Children and adolescents with MS had abnormal BAEP responses, with delayed neural conduction between the cochlear nucleus and the lateral lemniscus. Also, abnormal LLAEP results suggest a decrease in neural processing speed and auditory sensory discrimination response.

Effects of multiple sclerosis on the audio-vestibular system: a systematic review

OBJECTIVE

Systematically investigate the effects of multiple sclerosis (MS) on the audio-vestibular system.

METHODS

Systematic review of literature investigating audio-vestibular conditions in persons with MS (PwMS) aged ≥18 years. PubMed, Scopus, NICE and Web of Science were searched. Randomised controlled trials, and cohort, case-control, observational and retrospective studies in English, published from 2000 to 21 November 2021, evaluated PwMS with at least one outcome (pure tone audiometry, auditory brainstem response, otoacoustic emissions, cortical auditory evoked potentials, functional MRI assessing auditory function, vestibular evoked myogenic potentials, videonystagmography, electronystagmography, posturography, rotary chair, gaps in noise, word discrimination scores, duration pattern sequence test), were included. Study selection and assessments of bias were independently conducted by two reviewers using the Risk of Bias Assessment Tool for Non-randomized Studies, Newcastle-Ottawa Scale (NOS) and the NOS adapted for cross-sectional studies.

RESULTS

35 studies were included. Auditory function was evaluated in 714 PwMS and 501 controls, vestibular function was evaluated in 682 PwMS and 446 controls. Peripheral auditory function results were contradictory between studies; some found abnormalities in PwMS, and others found no differences. Tests of brainstem and central auditory functions were more consistently found to be abnormal in PwMS. Most vestibular tests were reported as abnormal in PwMS, abnormalities were either peripheral or central or both. However, quantitative analyses could not be performed due to discrepancies between studies in results reporting, test stimulus and recording parameters.

CONCLUSIONS

Although abnormal results on auditory and vestibular tests were noted in PwMS, specific effects of MS on the audio-vestibular system could not be determined due to the heterogeneity between studies that restricted the ability to conduct any quantitative analyses. Further research with consistent reporting, consistent stimulus and consistent recording parameters is needed in order to quantify the effects of MS on the auditory and vestibular systems.

PROSPERO REGISTRATION NUMBER

CRD42020180094.

Assessment of Visual and Brainstem Auditory Evoked Potentials in Patients with Hashimoto's Thyroiditis

BACKGROUND

The present study was aimed to evaluate parameters of visual and brainstem auditory evoked potentials (VEP, BAEP) in euthyreotic Hashimoto's thyroiditis (HT) patients without central nervous system involvement.

METHODS

100 HT patients (92 women, 8 men), mean age 46.9 years, and 50 healthy controls. They underwent a neurological examination, thyroid hormone levels, thyroid autoantibody titers, and brain imaging. Latencies and amplitudes of the N75, P100, and N145 component of VEP and the I-V components of BAEP were analyzed.

RESULTS

The neurological examination revealed in 31 patients signs of increased neurovegetative excitability. Brain resonance imaging showed no abnormalities in HT patients. The mean P100, relative P100, and N145 VEP latencies were significantly longer, and P100 amplitude significantly higher in HT patients than the controls. HT patients also had a longer mean wave BAEP V latency and mean wave III-V and I-V interpeak latencies, and significantly lower mean wave I and V amplitudes. Abnormal VEP and BAEP were recorded in 34% of the patients. There were no statistically significant correlations between the mean VEP parameters and thyroid profile and the applied dose of L-thyroxine. There was a relationship between the level of TSH and the wave BAEP III-V interpeak latency.

CONCLUSIONS

There were changes in the brain's bioelectrical activity in one-third of the patients with HT without nervous system involvement. The increased amplitude of the VEP may indicate increased cerebral cortex activity. Disorders of the brain's bioelectrical activity in the course of HT may be associated with an autoimmune process.

Alleviation of extensive visual pathway dysfunction by a remyelinating drug in a chronic mouse model of multiple sclerosis

Visual deficits are among the most prevalent symptoms in patients with multiple sclerosis (MS). To understand deficits in the visual pathway during MS and potential treatment effects, we used experimental autoimmune encephalomyelitis (EAE), the most commonly used animal model of MS. The afferent visual pathway was assessed in vivo using optical coherence tomography (OCT), electroretinography (ERG), and visually evoked cortical potentials (VEPs). Inflammation, demyelination, and neurodegeneration were examined by immunohistochemistry ex vivo. In addition, an immunomodulatory, remyelinating agent, the estrogen receptor β ligand chloroindazole (IndCl), was tested for its therapeutic potential in the visual pathway. EAE produced functional deficits in visual system electrophysiology, including suppression of ERG and VEP waveform amplitudes and increased signal latencies. Therapeutic IndCl rescued overall visual system latency by VEP but had little impact on amplitude or ERG findings relative to vehicle. Faster VEP conduction in IndCl-treated mice was associated with enhanced myelin basic protein signal in all visual system structures examined. IndCl preserved retinal ganglion cells (RGCs) and oligodendrocyte density in the prechiasmatic white matter, but similar retinal nerve fiber layer thinning by OCT was noted in vehicle and IndCl-treated mice. Although IndCl differentially attenuated leukocyte and astrocyte staining signal throughout the structures analyzed, axolemmal varicosities were observed in all visual fiber tracts of mice with EAE irrespective of treatment, suggesting impaired axonal energy homeostasis. These data support incomplete functional recovery of VEP amplitude with IndCl, as fiber tracts displayed persistent axon pathology despite remyelination-induced decreases in latencies, evidenced by reduced optic nerve g-ratio in IndCl-treated mice. Although additional studies are required, these findings demonstrate the dynamics of visual pathway dysfunction and disability during EAE, along with the importance of early treatment to mitigate EAE-induced axon damage.

Brainstem auditory-evoked response in healthy African pygmy hedgehogs (Atelerix albiventris)

OBJECTIVES

To evaluate and describe brainstem auditory-evoked response measurements in healthy African pygmy hedgehogs (Atelerix albiventris).

MATERIALS AND METHODS

Brainstem auditory-evoked response measurements were performed in 12 adult African pygmy hedgehogs (seven males, five females) under general anaesthesia. Waveform morphology was assessed and wave latencies, amplitudes and interpeak latencies calculated.

RESULTS

Brainstem auditory-evoked response measurements were successfully performed in both ears from all hedgehogs. Three distinct waves were reproducible in all patients in both ears using a stimulus with an intensity of 90 dB nHL (decibel above normal hearing level). Amplitudes of waves I and V, latencies of waves I, II-III and V and interpeak latencies of waves I-V were calculated at 90 dB for both ears of each animal.

CLINICAL SIGNIFICANCE

This study describes normal brainstem auditory-evoked response morphology and latencies for African pygmy hedgehogs. General anaesthesia is required to perform this neurodiagnostic, given the unique behaviour and anatomy of hedgehogs. This baseline data may be useful for investigating hearing abnormalities and central nervous system disorders in hedgehogs.

Brainstem auditory evoked potentials in patients with primary Sjögren's syndrome without central nervous system involvement

OBJECTIVES

Primary Sjögren's syndrome (pSS) is an autoimmune, multisystem exocrinopathy characterized by dysfunction of the exocrine glands. Central nervous system (CNS) involvement is estimated to be present in 10-60% patients with pSS. The present study aimed to evaluate brainstem auditory evoked potentials (BAEP) in pSS patients without central nervous system involvement, and without otolaryngological abnormalities.

METHOD

Thirty-six pSS patients (35 women, 1 man, mean age 48 years old) and 40 healthy volunteers were investigated. BAEP, brain imaging, laboratory parameters, and clinical neurological and otolaryngological examinations were performed.

RESULTS

Abnormal BAEP were recorded in 16.7% patients. The mean wave BAEP I and V latency and mean wave III-V and I-V interpeak latencies were significantly longer in pSS patients than the controls. There were no statistically significant correlations between BAEP parameters and laboratory tests. None of the patients was found having the abnormalities on brain imaging.

CONCLUSIONS

This study confirms that in pSS patients without clinical central nervous system impairment, auditory pathway disturbances could be found. Disorders of brain bioelectrical activity may be a consequence of ongoing autoimmune process. Key Points • BAEP abnormalities confirmed the clinically observed involvement of the central nervous system in patients with pSS. • Brain bioelectrical activity dysfunctions in pSS patients may be a consequence of ongoing inflammatory and/or immunological processes.

Measuring network disruption in neurodegenerative diseases: New approaches using signal analysis

Advanced neuroimaging has increased understanding of the pathogenesis and spread of disease, and offered new therapeutic targets. MRI and positron emission tomography have shown that neurodegenerative diseases including Alzheimer's disease (AD), Lewy body dementia (LBD), Parkinson's disease (PD), frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) are associated with changes in brain networks. However, the underlying neurophysiological pathways driving pathological processes are poorly defined. The gap between what imaging can discern and underlying pathophysiology can now be addressed by advanced techniques that explore the cortical neural synchronisation, excitability and functional connectivity that underpin cognitive, motor, sensory and other functions. Transcranial magnetic stimulation can show changes in focal excitability in cortical and transcortical motor circuits, while electroencephalography and magnetoencephalography can now record cortical neural synchronisation and connectivity with good temporal and spatial resolution.Here we reflect on the most promising new approaches to measuring network disruption in AD, LBD, PD, FTD, MS, and ALS. We consider the most groundbreaking and clinically promising studies in this field. We outline the limitations of these techniques and how they can be tackled and discuss how these novel approaches can assist in clinical trials by predicting and monitoring progression of neurophysiological changes underpinning clinical symptomatology.

Central fatigue in multiple sclerosis: a review of the literature

CONCEPT

Fatigue is a major concern for patients with multiple sclerosis (MS). A clear definition of MS-related fatigue is a prerequisite for appropriate instruments for fatigue assessment. In turn, accurate assessment of fatigue in MS will enhance exploration of plausible mechanisms underlying this common and distressing symptom. Content/Objectives: To provide an integrative review of the current literature on theoretical models used to study fatigue in MS, instruments used to assess fatigue and other factors that impact fatigue during the various phases of MS.

DATA SOURCES

PUBMED, OVID, Ovid Health Star, Ovid MEDINE, CINAHL, Health and Psychosocial Instruments (HaPI), and PsycINFO. Seventeen articles fit the inclusion criteria and were included in the review.

RESULTS

Definitions of MS-related fatigue are reviewed. Several studies found a link with neurotransmitter dysfunction, circadian rhythm, and the timing of fatigue. Central fatigue in MS is associated with neurotransmitters disruptions as well as circadian rhythm disorders, but the evidence is not strong. Perceptions of fatigue or fatigability may arise as either a primary or secondary manifestation of disease. Based on findings from the literature review, a theoretical model of fatigue in MS is proposed.

CONCLUSION

Future research on MS-related fatigue may consider a longitudinal design with a carefully selected self-report instrument to advance understanding of the underlying pathological mechanisms.

Event-related potentials and cognitive performance in multiple sclerosis patients with fatigue

The aim of this study was to evaluate event-related potentials (ERP) and cognition in multiple sclerosis (MS) patients with regard to fatigue and disease-related variables. The study comprised 86 MS patients and 40 controls. Fatigue was assessed using the Fatigue Severity Scale (FSS/FSS-5) and the Modified Fatigue Impact Scale (MFIS/MFISmod). N200 and P300 components of auditory ERP were analyzed. Cognition was evaluated by means of Brief Repeatable Battery of Neuropsychological Tests (BRBNT). The results of ERP and BRBNT were compared between non-fatigued, moderately and severely fatigued MS patients and controls. P300 latency was significantly longer in the whole MS group and in the fatigued patients than in the controls. A positive correlation was found between P300 latency and MFIS/MFISmod results, independent from age and MS-related variables. The fatigued patients scored less than non-fatigued ones in tests evaluating memory, visuomotor abilities and attention. Results of these tests correlated significantly with fatigue measures, independently from MS-related variables. Fatigue in MS patients showed significant relationships with impairment within the memory and attention domains. Parameters of auditory ERP, as electrophysiological biomarkers of cognitive performance, were not independently linked to fatigue.

Delayed P100-Like Latencies in Multiple Sclerosis: A Preliminary Investigation Using Visual Evoked Spread Spectrum Analysis

Conduction along the optic nerve is often slowed in multiple sclerosis (MS). This is typically assessed by measuring the latency of the P100 component of the Visual Evoked Potential (VEP) using electroencephalography. The Visual Evoked Spread Spectrum Analysis (VESPA) method, which involves modulating the contrast of a continuous visual stimulus over time, can produce a visually evoked response analogous to the P100 but with a higher signal-to-noise ratio and potentially higher sensitivity to individual differences in comparison to the VEP. The main objective of the study was to conduct a preliminary investigation into the utility of the VESPA method for probing and monitoring visual dysfunction in multiple sclerosis. The latencies and amplitudes of the P100-like VESPA component were compared between healthy controls and multiple sclerosis patients, and multiple sclerosis subgroups. The P100-like VESPA component activations were examined at baseline and over a 3-year period. The study included 43 multiple sclerosis patients (23 relapsing-remitting MS, 20 secondary-progressive MS) and 42 healthy controls who completed the VESPA at baseline. The follow-up sessions were conducted 12 months after baseline with 24 MS patients (15 relapsing-remitting MS, 9 secondary-progressive MS) and 23 controls, and again at 24 months post-baseline with 19 MS patients (13 relapsing-remitting MS, 6 secondary-progressive MS) and 14 controls. The results showed P100-like VESPA latencies to be delayed in multiple sclerosis compared to healthy controls over the 24-month period. Secondary-progressive MS patients had most pronounced delay in P100-like VESPA latency relative to relapsing-remitting MS and controls. There were no longitudinal P100-like VESPA response differences. These findings suggest that the VESPA method is a reproducible electrophysiological method that may have potential utility in the assessment of visual dysfunction in multiple sclerosis.