Multifocal VEP assessment of optic neuritis evolution

RXR agonist, 9-cis-13,14-dihydroretinoic acid (9CDHRA), reduces damage and protects from demyelination in transsynaptic degeneration model

Neurodegenerative and demyelinating disease, such as multiple sclerosis (MS) are at the forefront of medical research and the discovery of new drugs and therapeutics. One phenomenon of degeneration seen in these diseases is transsynaptic degeneration (TSD), where damage from one axon spreads to the other axons that are connected to it synaptically. It has previously been found that demyelination occurs prior to neuronal loss in an experimental form of induced TSD. Retinoid-x receptor (RXR) agonists have been shown to promote remyelination. Therefore, this study aimed to reveal the effects of a novel endogenous RXR-γ agonist, 9-cis-13,14-dihydroretinoic acid (9CDHRA), on preventing or restoring the effects of TSD. 9CDHRA was administered to mice following optic nerve crush (ONC) procedures, and electrophysiology (visual evoked potential, VEP) and histological (immunofluorescent) assessments were performed. It was found that 9CDHRA treatment effectively delayed glial activation and reduced the presence of apoptosis at the site of injury and further anterogradely in the visual system, including the lateral geniculate nucleus (LGN) and primary visual cortex (V1). Most notably, 9CDHRA was able to maintain myelin levels following ONC, and effectively protected from demyelination. This was corroborated by VEP recordings with improved P1 latency. The promising findings regarding the injury attenuating and myelin protecting properties of 9CDHRA necessitates further investigations into the potential therapeutic uses of this compound.

Visual evoked potentials in multiple sclerosis: P100 latency and visual pathway damage including the lateral geniculate nucleus

OBJECTIVE

To explore associations of the main component (P100) of visual evoked potentials (VEP) to pre- and postchiasmatic damage in multiple sclerosis (MS).

METHODS

31 patients (median EDSS: 2.5), 13 with previous optic neuritis (ON), and 31 healthy controls had VEP, optical coherence tomography and magnetic resonance imaging. We tested associations of P100-latency to the peripapillary retinal nerve fiber layer (pRNFL), ganglion cell/inner plexiform layers (GCIPL), lateral geniculate nucleus volume (LGN), white matter lesions of the optic radiations (OR-WML), fractional anisotropy of non-lesional optic radiations (NAOR-FA), and to the mean thickness of primary visual cortex (V1). Effect sizes are given as marginal R2 (mR2).

RESULTS

P100-latency, pRNFL, GCIPL and LGN in patients differed from controls. Within patients, P100-latency was significantly associated with GCIPL (mR2 = 0.26), and less strongly with OR-WML (mR2 = 0.17), NAOR-FA (mR2 = 0.13) and pRNFL (mR2 = 0.08). In multivariate analysis, GCIPL and NAOR-FA remained significantly associated with P100-latency (mR2 = 0.41). In ON-patients, P100-latency was significantly associated with LGN volume (mR2 = -0.56).

CONCLUSIONS

P100-latency is affected by anterior and posterior visual pathway damage. In ON-patients, damage at the synapse-level (LGN) may additionally contribute to latency delay.

SIGNIFICANCE

Our findings corroborate post-chiasmatic contributions to the VEP-signal, which may relate to distinct pathophysiological mechanisms in MS.

Objective detection of visual field defects with multifrequency VEPs

PURPOSE

To correlate multifrequency pattern reversal VEPs in quadrants (QmfrVEPs) with perimetric field losses for objective detection of visual field losses.

METHODS

QmfrVEP measurements were performed using four LED-based checkerboard stimulators to stimulate the four quadrants of the visual field. QmfrVEPs were measured monocularly in 5 normal subjects and in 5 glaucoma patients who showed losses in conventional Octopus perimetry. The pattern reversal frequency varied slightly between the stimulators: (11.92, 12.00, 12.08 and 12.16 reversals/sec). The responses to the different stimuli were identified by discrete Fourier analysis. VEPs were recorded using different electrode configurations, and the recording with the highest signal-to-noise ratio (SNR) was used for further analysis.

RESULTS

QmfrVEP responses from the different quadrants can be reliably measured and separated using the 0.08 reversals/sec interstimulus reversal frequency differences. The signal-to-noise ratio in the four quadrants was significantly correlated with the equivalent visual field losses obtained with perimetry (Spearman rank correlation: P < 0.001). In the five glaucoma patients, the SNR was reduced in 15 out of the 16 quadrants with a perimetric defect, in comparison to the results in quadrants of healthy subjects. This confirms the sensitivity of the procedure.

CONCLUSION

QmfrVEP responses can be measured reliably. This pilot study suggests that high SNR values exclude visual field defects and that focal defects can be identified in glaucoma patients.

TRIAL REGISTRATION

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The Evolvement of OCT and OCT-A in Identifying Multiple Sclerosis Biomarkers

The prevalence of multiple sclerosis (MS) has been increasing among young people in developing countries over the last years. With the continuous development of new technology, the diagnosis and follow-up of these patients has received new parameters that physicians may use in their practice. This paper reviews the main biomarkers identified through Optical Coherence Tomography Angiography (OCT-A) involved in the development and progression of MS and investigates the role it may have in detecting changes to the central nervous system (CNS).

Early predictors of visual and axonal outcomes after acute optic neuritis

Background

Predicting long-term visual outcomes and axonal loss following acute optic neuritis (ON) is critical for choosing treatment. Predictive models including all clinical and paraclinical measures of optic nerve dysfunction following ON are lacking.

Objectives

Using a prospective study method, to identify 1 and 3 months predictors of 6 and 12 months visual outcome (low contrast letter acuity 2.5%) and axonal loss [retinal nerve fiber layer thickness and multifocal evoked potential (mfVEP) amplitude] following acute ON.

Methods

In total, 37 patients of acute ON onset were evaluated within 14 days using between-eye asymmetry of visual acuity, color vision (Ishihara plates), optical coherence tomography, mfVEP, and optic nerve magnetic resonance imaging [magnetic transfer ratio (MTR) and diffusion tensor imaging (DTI)].

Results

Visual outcome at 6 and 12 months was best predicted by Ishihara asymmetry at 1 and 3 months following ON onset. Axonal loss at 6 and 12 months was reliably predicted by Ishihara asymmetry at 1 month. Optic nerve MTR and DTI at 3 months post-acute ON could predict axonal loss at 6 and 12 months.

Conclusions

Simple Ishihara asymmetry testing 1 month after acute ON onset can best predict visual outcome and axonal loss at 6 and 12 months in a clinical or research setting.

The clinical application of critical flicker fusion frequency in demyelinating optic neuritis

Purpose

To investigate the application of critical flicker fusion frequency (CFF) in demyelinating optic neuritis (DON).

Methods

A cross-sectional study. A total of 127 eyes in 69 DON patients and 63 eyes in 33 healthy control (HC) groups were included between January 2021 to September 2021 from Department of Ophthalmology, PLA General Hospital. Patients underwent best-corrected visual acuity (BCVA), visual field, optical coherence tomography (OCT), flash visual evoked potential (F-VEP), and CFF examinations. The affected eyes were divided into aquaporins 4 (AQP4-), myelin oligodendrocyte glycoprotein (MOG-), and double negative DON according to serum antibody; mild, moderate, severe degree visual impairment according to BCVA ≥ 0.5, 0.1-0.5, < 0.1; and 4 groups: < 1, 1 ∼< 3, 3 ∼ < 6 and > 6 months according to time interval from onset to CFF examination. One-way ANOVA was used to perform above subgroup analysis. The correlations between CFF and F-VEP peak time, peak value, BCVA and mean visual filed defect (MD) were analyzed in order via Pearson correlation analysis.

Results

he trichromatic values of red, green, and yellow in DON affected eyes were 21.83 ± 9.03, 23.66 ± 10.21, 24.09 ± 10.77 Hz, respectively, which was significantly reduced compared with the HC group (t = -14.82, -14.22, -14.00; P < 0.001). The subgroup analysis showed no significant difference between different antibody subtypes (P = 0.914 <0.848 <0.604), whereas, a significant decrease of CFF trichromatic value was found in severe visual acuity impairment group (P < 0.001). There was a significant difference in CFF- trichromatic values at different time points (P < 0.001), to be specific, CFF fluctuated under 20Hz within 3 months after onset and tended to be stable around 24-28Hz. Correlation analysis showed that the peak time of F-VEP (r = -0.486, -0.515, -0.526; P < 0.001), BVCA (r = -0.640, -0.659, -0.642; P < 0.001), were negatively correlated with CFF trichromatic values, MD and CFF were positively correlated (r = 0.486, 0.453, 0.476; P = 0.003, 0.006, 0.004).

Conclusions

A significant decrease of CFF value was found in DON-affected eyes, and it has a good correlation with BCVA, MD and latency of F-VEP, and can better reflect the impairment of visual function.

Multifocal visual evoked potential evaluation for diagnosis of acute optic neuritis and for prediction of visual outcome and ganglion cell layer thinning following optic neuritis

BACKGROUND

While damage to the optic nerve following optic neuritis (ON) is readily quantifiable, the evaluation of prognosis for visual function and neuroaxonal loss in the acute ON is challenging.

OBJECTIVE

The objective of this study is to investigate the value of multifocal visual evoked potential (mfVEP) in acute ON, diagnostically for acute ON and prognostically for visual outcome and subsequent ganglion cell/inner plexiform layer thickness (GCLIPLt).

METHODS

A prospective cohort study of mfVEP and full-field visual evoked potential (ffVEP) in acute, unilateral ON (onset < 31 days) was conducted. Comparisons with healthy controls (n = 30) and association analysis with follow-up optical coherence tomography (OCT) measurements (of the GCLIPLt) and visual function (Sloan low-contrast visual acuity (LCVA)) were conducted.

RESULTS

Seventy-nine ON patients were included (mean: 17 days from onset). Excluding measurements with conduction block, ffVEP (n = 54) and mfVEP (n = 44) showed sensitivities of 89% and 84% to a specificity of 97%. 65/79 patients were re-examined (mean: 200 days follow-up). mfVEP amplitude and latency inter-eye asymmetry in acute ON correlated with GCLIPLt (r = 0.587 and Spearman's ρ = 0.597, for both, p < 0.001). mfVEP amplitude correlated with LCVA inter-eye asymmetry at follow-up (r = 0.421, p < 0.001), mfVEP latency did not.

CONCLUSION

mfVEP may support the prognostic evaluation of acute ON patients and prove valuable in future neuroprotective and remyelinating trials. In acute ON, the increase in diagnostic value of mfVEP to ffVEP may be limited due to widespread conduction block.

The contribution of multifocal visual evoked potentials in patients with optic neuritis and multiple sclerosis: a review

Purpose

To review the evidence on the usefulness of the multifocal visual evoked potential (mfVEP) test in patients with optic neuritis (ON) and/or multiple sclerosis (MS).

Methods

We critically review key published evidence on the use of mfVEP in ON/MS patients and its association with other functional and structural tests.

Results

Multifocal VEP tests are useful in detecting abnormality in patients with ON/MS and monitor the progression of lesions (remyelination, atrophy). In addition, mfVEP has good correlation with conventional visual evoked potential (VEP), standard automated perimetry, optical coherence tomography and magnetic resonance imaging. In patients with ON, mfVEP might be useful in predicting the risk of conversion to MS.

RETRACTED ARTICLE: Evaluation of macular thickness and visual pathways using optic coherence tomography and pattern visual evoked potential in different clinical stages of obstructive sleep apnea syndrome

AIM

The present study aimed to investigate and compare possible changes in amplitude and latency of pattern visual evoked potentials (PVEP) and thickness of quadrants of the macula (TQM) using optic coherence tomography (OCT).

MATERIALS AND METHODS

According to polysomnography examinations, 30 mild, 30 severe, 30 controls were included in the study after approval from the ethics committee.

RESULTS

No significant difference was found in age and gender between the groups (p = 0.184 and p = 0.954). Significant difference was found between external and internal superior TQM, mean thickness of ganglion cell layer in comparison of all three groups (p = 0.011, p = 0.047, p = 0.030). In comparison between severe OSAS and control groups, significant difference was found in internal nasal, internal superior and external superior TQM (p = 0.048, p = 0.033, p = 0.014) while no significant difference was found TQM in comparison between the mild OSAS and control groups. In comparison between the group of severe OSAS and controls, significant increase was found in P100 as well as N145 latencies whereas only P100 latency was found to increase when mild OSAS was compared with controls. No significant correlation was found between TQM and PVEP parameters in mild and severe OSAS patients.

DISCUSSION

Latency and amplitude of PVEP altered in OSAS because edema and inflammation was remarkable in mild as well as severe stages of the disease. Furthermore, thinning in the macula was observed only in severe stages of the disease, explained with level of atrophy and exposure to extended hypoxia.

Predictive value of optical coherence tomography, multifocal visual evoked potentials, and full-field visual evoked potentials of the fellow, non-symptomatic eye for subsequent multiple sclerosis development in patients with acute optic neuritis

BACKGROUND

Diagnosis of multiple sclerosis (MS) may sometimes be ascertained at the time of optic neuritis (ON) but other times require the advent of new disease activity.

OBJECTIVES

The aim of this study was to examine the predictive value of optical coherence tomography (OCT) and visual evoked potential (VEP) measurements of the non-symptomatic, fellow eye of ON patients, for conversion to MS.

METHODS

This is a prospective cohort study in patients with acute ON. OCT thickness measurements of peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell layer-inner plexiform layer (GCLIPL), and multifocal (mf) VEP and full-field (ff) VEP, were performed. Univariate and multivariate Cox regression examined the value of predictors for the conversion to MS.

RESULTS

A total of 79 unilateral, acute ON patients, with no MS diagnosis or prior demyelination, were included. Of which, 28 patients developed MS during follow-up. Inferonasal GCLIPL, mean GCLIPL, and pRNFL thickness significantly predicted MS development in multivariate analysis (hazard ratio (HR) = 0.922-0.939, p = 0.0172-0.021). MfVEP mean latency (HR = 1.052, p = 0.006) only predicted MS conversion in univariate analysis. No significant predictive value was shown for the other parameters (p > 0.2).

CONCLUSION

While both mfVEP and OCT are useful tools in the evaluation of acute ON patients, only OCT measurements of fellow eyes may serve as an independent predictor of MS development.

Visual Evoked Potentials as a Biomarker in Multiple Sclerosis and Associated Optic Neuritis

: ABSTRACT:: Multiple sclerosis (MS) is an inflammatory, degenerative disease of the central nervous system (CNS) characterized by progressive neurological decline over time. The need for better "biomarkers" to more precisely capture and track the effects of demyelination, remyelination, and associated neuroaxonal injury is a well-recognized challenge in the field of MS. To this end, visual evoked potentials (VEPs) have a role in assessing the extent of demyelination along the optic nerve, as a functionally eloquent CNS region. Moreover, VEPs testing can be used to predict the extent of recovery after optic neuritis (ON) and capture disabling effects of clinical and subclinical demyelination events in the afferent visual pathway. In this review, the evolving role of VEPs in the diagnosis of patients with ON and MS and the utility of VEPs testing in determining therapeutic benefits of emerging MS treatments is discussed.

Evaluation of retinal fiber thickness and visual pathways with optic coherence tomography and pattern visual evoked potential in different clinical stages of obstructive sleep apnea syndrome

PURPOSE

To investigate the possible changes in retinal nerve fiber layer (RNFL) by optic coherence tomography and in the amplitudes and peak times (PTs) in pattern visual evoked potential (pVEP) and to compare them in obstructive sleep apnea syndrome (OSAS).

METHODS

This prospective study included patients with mild OSAS (n = 30), severe OSAS (n = 30), and 30 control subjects. All patients were assessed after obtaining the approval from our hospital's ethics committee.

RESULTS

There was no difference in age and gender between the groups (p = 0.184, p = 0.954). By analysis of variance, there was a significant difference in RNFL values among patients with mild OSAS, severe OSAS, and control for three measures of RNFL (average p = 0.044, nasal p = 0.003, inferior p = 0.027). In severe OSAS group, nasal and inferior quadrants of the RNFL were found to be thinner than the control group (p = 0.008, p = 0.031). We showed that the PT of P100 and N145 was prolonged in severe OSAS compared to the control group (p < 0.001) and that PT of P100 was prolonged in mild OSAS compared to the control group (p < 0.05). The amplitude of N75-P100 was significantly decreased in patients with both severe OSAS and mild OSAS compared to the control group (p < 0.001). Correlation of RNFL and pVEP values showed that the inferior quadrant RNFL thickness is correlated with both P100 and N145 PTs (r = 0.271*, p = 0.036 and r = 0.290*, p = 0.043, respectively) and N75-P100 amplitude (r = 0.378**, p = 0.003) in severe OSAS group.

CONCLUSIONS

In mild and severe stages of the disease, edema and inflammation were evident and VEP PT and amplitudes were affected in both groups. Furthermore, thinning in RNFL in the severe stage of the disease might be associated with higher atrophy levels and prolonged exposure to hypoxia.

A computer-aided diagnosis of multiple sclerosis based on mfVEP recordings

Introduction

The aim of this study is to develop a computer-aided diagnosis system to identify subjects at differing stages of development of multiple sclerosis (MS) using multifocal visual-evoked potentials (mfVEPs). Using an automatic classifier, diagnosis is performed first on the eyes and then on the subjects.

Patients

MfVEP signals were obtained from patients with Radiologically Isolated Syndrome (RIS) (n = 30 eyes), patients with Clinically Isolated Syndrome (CIS) (n = 62 eyes), patients with definite MS (n = 56 eyes) and 22 control subjects (n = 44 eyes). The CIS and MS groups were divided into two subgroups: those with eyes affected by optic neuritis (ON) and those without (non-ON).

Methods

For individual eye diagnosis, a feature vector was formed with information about the intensity, latency and singular values of the mfVEP signals. A flat multiclass classifier (FMC) and a hierarchical classifier (HC) were tested and both were implemented using the k-Nearest Neighbour (k-NN) algorithm. The output of the best eye classifier was used to classify the subjects. In the event of divergence, the eye with the best mfVEP recording was selected.

Results

In the eye classifier, the HC performed better than the FMC (accuracy = 0.74 and extended Matthew Correlation Coefficient (MCC) = 0.68). In the subject classification, accuracy = 0.95 and MCC = 0.93, confirming that it may be a promising tool for MS diagnosis.

Conclusion

In addition to amplitude (axonal loss) and latency (demyelination), it has shown that the singular values of the mfVEP signals provide discriminatory information that may be used to identify subjects with differing degrees of the disease.

Novel uses of retinal imaging with optical coherence tomography in multiple sclerosis

Introduction: Multiple Sclerosis (MS) is the most common chronic autoimmune neuroinflammatory condition in young adults. It is often accompanied by optic neuritis (ON) and retinal neuro-axonal damage causing visual disturbances. Optical coherence tomography (OCT) is a sensitive non-invasive method for quantifying intraretinal layer volumes. Recently, OCT not only showed to be a reliable marker for ON-associated damage, but also proved its high prognostic value for functional outcome and disability accrual in patients with MS. Consequently, OCT is discussed as a potential marker for monitoring disease severity and therapeutic response in individual patients. Areas covered: This article summarizes our current understanding of structural retinal changes in MS and describes the future potential of OCT for differential diagnosis, monitoring of the disease course and for clinical trials. Expert commentary: Today, OCT is used in clinical practice in specialized MS centers. Standardized parameters across devices are urgently needed for supporting clinical utility. Novel parameters are desirable to increase sensitivity and specificity in terms of MS.

Mechanism of delayed conduction of fellow eyes in patients with optic neuritis

To test the hypothesis that latency delay in the fellow eyes of optic neuritis (ON) patients and to compensate for delayed transmission of visual information, latency change of multi-focal visual evoked potential (mfVEP) traces in fellow eyes of 15 ON patients were analyzed. Patients with low risk (LR) for developing multiple sclerosis (MS) were examined separately from MS patients to isolate effect of cortical plasticity from potential pathological changes in disseminated disease. The small increase in latency in fellow eyes of LR group was statistically not significant. In MS patients, the latency was significantly delayed (P<0.02). The magnitude of the latency change in the fellow eyes did not correlate with the severity of latency delay in the affected eyes (R²<0.02, P=0.3). The differences between ON patients with and without MS, reported here, suggest that the presence of disseminated disease plays critical role in latency delay of the fellow eye.

Clinical evoked potentials in neurology: a review of techniques and indications

Evoked potentials (EPs) are a powerful and cost-effective tool for evaluating the integrity and function of the central nervous system. Although imaging techniques, such as MRI, have recently become increasingly important in the diagnosis of neurological diseases, over the past 30 years, many neurologists have continued to employ EPs in specific clinical applications. This review presents an overview of the recent evolution of 'classical' clinical applications of EPs in terms of early diagnosis and disease monitoring and is an extension of a previous review published in this journal in 2005 by Walsh and collaborators. We also provide an update on emerging EPs based on gustatory, olfactory and pain stimulation that may be used as clinically relevant markers of neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease and cortical or peripheral impaired pain perception. EPs based on multichannel electroencephalography recordings, known as high-density EPs, help to better differentiate between healthy subjects and patients and, moreover, they provide valuable spatial information regarding the site of the lesion. EPs are reliable disease-progression biomarkers of several neurological diseases, such as multiple sclerosis and other demyelinating disorders. Overall, EPs are excellent neurophysiological tools that will expand standard clinical practice in modern neurology.

Multifocal visual evoked potentials for quantifying optic nerve dysfunction in patients with optic disc drusen

PURPOSE

To explore the applicability of multifocal visual evoked potentials (mfVEPs) for research and clinical diagnosis in patients with optic disc drusen (ODD). This is the first assessment of mfVEP amplitude in patients with ODD.

METHODS

MfVEP amplitude and latency from 33 patients with ODD and 22 control subjects were examined. Mean amplitude, mean inner ring (IR) amplitude (0.87-5.67° of visual field) and mean outer ring amplitude (5.68-24° of visual field) were calculated using signal-to-noise ratio (SNR) and peak-to-peak analysis. Monocular latency was calculated using second peak analysis, while latency asymmetry was calculated using cross-correlation analysis.

RESULTS

Compared to normals, significantly decreased mean overall amplitude (p < 0.001), IR amplitude (p < 0.001) and outer ring amplitude (p < 0.001) were found in ODD patients when using SNR. An overall monocular latency delay of 7 ms was seen in ODD patients (p = 0.001). A significant correlation between amplitude and automated perimetric mean deviation as well as retinal nerve fibre layer thickness was found (respectively, p < 0.001 and p = 0.003). The overall highest correlation was found in this order: outer ring, full eye and IR. In the control group, SNR intersubject variability was 17.6% and second peak latency intersubject variability was 2.8%.

CONCLUSION

Decreased mfVEP amplitude in patients with ODD suggests a direct mechanical compression of the optic nerve axons. Our results suggest that mfVEP amplitude is applicable for the assessment of optic nerve dysfunction in patients with ODD.

Multifocal visual evoked potentials in optic neuritis and multiple sclerosis: A review

Multifocal visual evoked potential (mf-VEP) represents a new approach to the classical full field (ff-)VEP with separate responses from up to 60 sectors of the visual field. A thorough literature survey of the use of mf-VEP in optic neuritis (ON) and multiple sclerosis (MS) is presented (38 published studies were retrieved). Mf-VEP provides direct topographical information of specific lesions and facilitates investigations on structural-functional correlations thus providing new methods for exploring the interplay between demyelination, atrophy and remyelination in MS. Good correlation was shown between mf-VEP and OCT, ff-VEP, MRI (MTR, DTI), 30-2 standard automated perimetry and low-contrast-visual acuity. All but one study showed superior sensitivity and specificity compared to ff-VEP, especially with regards to small, peripheral lesions or lesions of the upper visual field. Mf-VEP has shown superior sensitivity and specificity than established methods in diagnosing optic nerve lesions and tracking functional recovery following lesions. Abnormal mf-VEP responses in the fellow, non-ON afflicted eye may predict MS risk in ON patients. No standardization currently exists and no direct comparisons in ON and MS between at least 5 different commercially available mf-VEP systems have so far been published. Despite these limitations, mf-VEP is a promising new tool of diagnostic and prognostic value of mf-VEP in ON and MS.

White and Gray Matter Volume Changes and Correlation with Visual Evoked Potential in Patients with Optic Neuritis: A Voxel-Based Morphometry Study

Background

The aim of this study was to investigate potential morphological alterations of gray and white matter in patients with optic neuritis (ON) and their relationship with behavioral performance, using voxel-based morphometry (VBM).

Material/Methods

Twelve (4 males, 8 females) patients with ON and 12 (4 males, 8 females) age-, sex-, and education-matched healthy controls (HCs) underwent magnetic resonance imaging (MRI). Imaging data were analyzed using two-sample t tests to identify group differences in gray and white matter volume (GMV, WMV). Correlation analysis was used to explore relationships between observed GMV and WMV of different areas and visual evoked potential (VEP) in ON.

Results

Compared with HCs, ON patients had: significantly decreased GMV in the left postcentral gyrus, left inferior frontal gyrus, left anterior cingulate, left and right middle frontal gyrus, and right inferior parietal lobule; decreased WMV in the left middle frontal gyrus, right superior frontal gyrus, left precentral gyrus and right inferior parietal lobule; and increased WMV in the left fusiform gyrus and left inferior parietal lobule. VEP latency of the right eye in ON correlated positively with WMV signal value of the left fusiform gyrus (r=0.726, p=0.008), and negatively with GMV signal value of the right inferior parietal lobule (r=−0.611, p=0.035). Duration of ON correlated negatively with WMV signal value of the right superior frontal gyrus (r=−0.662, p=0.019), while best-corrected visual acuity (VA) of the right eye correlated negatively with WMV signal value of the left middle frontal gyrus (r=−0.704, p=0.011).

Conclusions

These results suggest significant brain involvement in ON, which may reflect the underlying pathologic mechanism. Correlational results demonstrate that VEP in ON is closely associated with WMV and GMV atrophy in many brain regions.

Evaluation of the Innermost Retinal Layers and Visual Evoked Potentials in Patients with Multiple Sclerosis

PURPOSE

The present study was conducted to investigate alterations in the innermost layers of the retina using optical coherence tomography (OCT) and to assess potential associations of structural measures with functional markers in patients with Multiple Sclerosis (MS).

MATERIALS AND METHODS

Ninety-four eyes of 47 MS patients and 60 eyes of 30 healthy individuals were included in the study. All patients underwent complete ophthalmological examination and OCT imaging to analyze peripapillary retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) thickness. Visual evoked potentials (VEPs) and expanded disability status scale (EDSS) score were assessed for MS patients.

RESULTS

The average RNFL and GCIPL thicknesses were thinner in MS patients (86.2 ± 11.9 µm and 73.6 ± 9.7 µm, respectively) when compared with those of healthy controls (96.7 ± 8.2 µm and 85.9 ± 4.6 µm, respectively, p < 0.001 for both). Within MS patients, the average RNFL and GCIPL thicknesses were lower in eyes with a prior history of optic neuritis (MS ON) than in eyes with no optic neuritis history (MS non-ON) (p = 0.012 and p < 0.001, respectively). RNFL and GCIPL thicknesses were inversely correlated with VEP latency (r = -0.40, p < 0.001 and r = -0.36, p < 0.001, respectively) in MS patient eyes. There was a correlation between GCIPL thickness and VEP amplitude in eyes with previous ON history (r = 0.34, p = 0.035). No significant correlations were found between OCT measurements and EDSS score.

CONCLUSIONS

Innermost layers of the retina are highly affected by the pathophysiologic process in MS disease, manifesting as a reduction in RNFL and GCIPL thickness. The structural retinal changes show correlation with alterations in potentials showing the optic pathway function.

Optic Nerve Dysfunction in Obstructive Sleep Apnea: An Electrophysiological Study

STUDY OBJECTIVES

The aim of this study was to evaluate the integrity of the visual system in patients affected by obstructive sleep apnea (OSA) by means of electroretinogram (ERG) and visual evoked potential (VEP).

METHODS

We performed electrophysiological study of the visual system in a population of severe OSA (apnea-hypopnea events/time in bed ≥ 30/h) patients without medical comorbidities compared to a group of healthy controls similar for age, sex, and body mass index. Patients and controls did not have visual impairment or systemic disorders with known influence on the visual system. ERG and VEP were elicited by a reversal pattern generated on a television monitor at low (55') and high (15') spatial frequencies stimulation. Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS) in both patients and controls.

RESULTS

In comparison with healthy controls (n = 27), patients with OSA (n = 27) showed a significant latency delay coupled with a significant amplitude reduction of P100 wave of VEP at all spatial frequencies in both eyes. No significant differences between groups were detected as concerning ERG components. No correlations were found between polygraphic parameters, ESS scores, or VEP and ERG components in OSA patients.

CONCLUSIONS

This study documented that patients with OSA, without medical comorbidities, present VEP alteration as documented by lower amplitude and longer latency of the P100 component than healthy controls. These altered electrophysiological findings may be the expression of optic nerve dysfunction provoked by hypoxia, acidosis, hypercarbia and airway obstruction, frequently observed in patients with OSA. Hence, we hypothesize that OSA per se may impair optic nerve function.

Steady-state multifocal visual evoked potential (ssmfVEP) using dartboard stimulation as a possible tool for objective visual field assessment

PURPOSE

To investigate whether a conventional, monitor-based multifocal visual evoked potential (mfVEP) system can be used to record steady-state mfVEP (ssmfVEP) in healthy subjects and to study the effects of temporal frequency, electrode configuration and alpha waves.

METHODS

Multifocal pattern reversal VEP measurements were performed at 58 dartboard fields using VEP recording equipment. The responses were measured using m-sequences with four pattern reversals per m-step. Temporal frequencies were varied between 6 and 15 Hz. Recordings were obtained from nine normal subjects with a cross-shaped, four-electrode device (two additional channels were derived). Spectral analyses were performed on the responses at all locations. The signal to noise ratio (SNR) was computed for each response using the signal amplitude at the reversal frequency and the noise at the neighbouring frequencies.

RESULTS

Most responses in the ssmfVEP were significantly above noise. The SNR was largest for an 8.6-Hz reversal frequency. The individual alpha electroencephalogram (EEG) did not strongly influence the results. The percentage of the records in which each of the 6 channels had the largest SNR was between 10.0 and 25.2 %.

CONCLUSION

Our results in normal subjects indicate that reliable mfVEP responses can be achieved by steady-state stimulation using a conventional dartboard stimulator and multi-channel electrode device. The ssmfVEP may be useful for objective visual field assessment as spectrum analysis can be used for automated evaluation of responses. The optimal reversal frequency is 8.6 Hz. Alpha waves have only a minor influence on the analysis. Future studies must include comparisons with conventional mfVEP and psychophysical visual field tests.

Visual pathways involvement in clinically isolated syndrome in children

AIM

To investigate extent and nature of visual pathways involvement in children with clinically isolated syndrome (CIS).

METHODS

Forty-seven patients (age 11-17y) with CIS, which later proved to be multiple sclerosis (MS) onset, and 30 controls underwent visual evoked potentials (VEP) investigation within 12d from the appearance of the first signs of disease. Latency and amplitude of P100 peak were compared with normative data and between groups.

RESULTS

In 58% patients, including those without signs of retrobulbar neuritis, significant slowing of conduction along the central visual pathways (P100 latency lengthening) is seen. P100 amplitudes drop (signs of axonal damage) are registered less frequently (29% cases).

CONCLUSION

The results indicate that visual pathways are often affected in the MS onset; mostly demyelination signs are seen. Despite MRI significance for MS diagnostic, VEPs proved to be still effective in early diagnosis of MS in children.