Visual Evoked Potentials Latency Research Articles

Longitudinal effects of prenatal alcohol exposure on visual neurodevelopment over infancy.

Prenatal alcohol exposure (PAE) affects neurodevelopment in over 59 million individuals globally. Prior studies using dichotomous categorization of alcohol use and comorbid substance exposures provide limited knowledge of how prenatal alcohol specifically impacts early human neurodevelopment. In this longitudinal cohort study from Cape Town, South Africa, PAE is measured continuously-characterizing timing, dose, and drinking patterns (i.e., binge drinking). High-density electroencephalography (EEG) during a visual-evoked potential (VEP) task was collected from infants aged 8 to 52 weeks with prenatal exposure exclusively to alcohol and matched on sociodemographic factors to infants with no substance exposure in utero. First trimester alcohol exposure related to altered timing of the P1 VEP component over the first 6 months postnatally, and first trimester binge drinking exposure altered timing of the P1 VEP components such that increased exposure was associated with longer VEP latencies while increasing age was related to shorter VEP latencies (n = 108). These results suggest alcohol exposure in the first trimester may alter visual neurodevelopmental timing in early infancy. Exploratory individual-difference analysis across infants with and without PAE tested the relation between VEP latencies and myelination for a subsample of infants with usable magnetic resonance imaging (MRI) T1w and T2w scans collected at the same time point as EEG (n = 47). Decreased MRI T1w/T2w ratios (an indicator of myelin) in the primary visual cortex (n = 47) were linked to longer P1 VEP latencies. Results from these two sets of analyses suggest that prenatal alcohol and postnatal myelination may both separately impact VEP latency over infancy. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Assessing the visual afferent pathway with the multifocal visual evoked potentials in the radiologically isolated syndrome

The early identification of individuals with radiologically isolated syndrome (RIS) who are at an elevated risk of progressing to multiple sclerosis (MS) is essential for making informed treatment decisions. This study aimed to evaluate the predictive potential of multifocal Visual Evoked Potentials (mfVEP) measures in individuals with RIS with respect to their conversion to MS. A prospective observational cohort study was conducted, involving 21 individuals with RIS recruited from a MS center. Baseline assessments, including mfVEP, magnetic resonance imaging (MRI), and clinical examinations, were performed, and participants were longitudinally followed for up to 24 months. The primary outcome measures were the conversion to MS. Over a clinical follow-up period of 24 months, five individuals (5/21) with RIS progressed to MS. MfVEP amplitude responses (interocular and monocular probability analysis) demonstrated abnormal cluster visual field defects in 47.6% of RIS eyes at baseline, whereas multifocal VEP latency analysis showed significant delays in 38.4%. A reduction in interocular amplitude [OR = 0.036, (95% CI 0.003–0.503); P = 0.014], monocular amplitude [OR = 0.083, (95% CI 0.007–0.982); P = 0.048], and a prolonged interocular latency [OR = 0.095, (95% CI 0.009–0.972); P = 0.047] were associated with a higher relative risk of clinical conversion at the 2-year follow-up. Multifocal VEP may serve as a novel and independent risk factor for predicting the conversion to MS in individuals with Radiologically Isolated Syndrome.

Effects of disease-modifying therapies on remyelination in multiple sclerosis; evaluation via visual evoked potential test

BackgroundAssessment of the visual pathway, which is frequently affected by MS, provides the opportunity to measure the remyelination of acute and chronic MS lesions in vivo and non-invasively. VEP can be used in this context. Amplitude is a parameter of axonal loss, whereas latency is an in vivo biomarker of myelin repair. This study aimed to evaluate DMT's neuroprotective and pro-remyelinating potential by evaluating VEP latency and amplitude in MS patients. Materials and methodsA total of 74 patients with relapsing MS who had no evidence of optic neuritis were included in the study. Patient data were retrospectively analyzed and recorded. In the VEP test, latency above 118 ms and amplitude below 5.0 μV were considered abnormal. Classified according to DMTs (injectables, teriflunomide, dimethyl fumarate, fingolimod, cladribine, and alemtuzumab). Visual evoked potential tests, clinical features, and cerebrospinal fluid examinations were evaluated by three independent neurologists and one clinical neurophysiologist. ResultsThe mean age at diagnosis was 29.2 ± 9.01, and the mean age at first VEP was 34.97 ± 10.64. In women, latency was lower, and amplitude was higher. The mean differences in latency and amplitude were, respectively, latency prolonged by 0.7 ms on the right and 0.5 ms on the left, and amplitude increased by 0.6 μV on the right and 0.37 μV on the left. However, these changes were not statistically significant. Latency worsening was more prominent in those with longer disease duration (p = 0.011). Those with amplitude or latency worsening had higher EDSS (p = 0.016 and 0.013, respectively). DMTs did not affect these changes. ConclusionProlonged latency is associated with a long disease duration. Deterioration in both amplitude and latency is evident in high EDSS. These results may be an indirect consequence of axonal degeneration dominating remyelination. DMTs do not ameliorate impaired remyelination and neurodegeneration but seem to be sufficient for short-term maintenance of the current state.

Comparison of Visual Evoked Potential Latency and Amplitude Values According to Visual Acuity among Normal Adult Eyes in dr. Cipto Mangunkusumo Hospital

Visual Evoked Potential (VEP) is a diagnostic procedure to evaluate pathological conditions affecting the visual pathway with several protocols, including pattern onset/offset VEP, flash VEP, and pattern-reversal VEP (PRVEP), standardized by International Society For Clinical Electrophysiology In Vision (ISCEV). PRVEP, the most common protocol used in clinical practice, is not always directly proportional to visual acuity (VA). Clarity of the refractory media and gender are presumed to affect it; thus, using PRVEP reference value based on refractory status is not casually applicable when the VA does not resemble refractory status. This study aims to determine the changes in VEP latency and amplitude value according to various subjective VA, and to examine and analyze these latency and amplitude values within male and female subject groups. The research was conducted at the Department of Ophthalmology, dr. Cipto Mangunkusumo Hospital from August to October 2017. Latency and amplitude values were measured with PRVEP. Measurement was performed on normal VA and defocus-induced VA to 6/18, 6/30, and 6/60 values, using small and large-sized checkerboard stimuli. Prolonged latency and decreased amplitude were found in male and female subject groups, corresponding with decreasing VA levels. Using 18 min arc and 48 min arc-sized checkerboards gave the closest result to the reference value. The difference in VEP value according to subjects' gender was found in amplitude but not in latency.

Comparison of Visual Evoked Potential Latency and Amplitude Values According to Visual Acuity among Normal Adult Eyes in dr. Cipto Mangunkusumo Hospital

Visual Evoked Potential (VEP) is a diagnostic procedure to evaluate pathological conditions affecting the visual pathway with several protocols, including pattern onset/offset VEP, flash VEP, and pattern-reversal VEP (PRVEP), standardized by International Society For Clinical Electrophysiology In Vision (ISCEV). PRVEP, the most common protocol used in clinical practice, is not always directly proportional to visual acuity (VA). Clarity of the refractory media and gender are presumed to affect it; thus, using PRVEP reference value based on refractory status is not casually applicable when the VA does not resemble refractory status. This study aims to determine the changes in VEP latency and amplitude value according to various subjective VA, and to examine and analyze these latency and amplitude values within male and female subject groups. The research was conducted at the Department of Ophthalmology, dr. Cipto Mangunkusumo Hospital from August to October 2017. Latency and amplitude values were measured with PRVEP. Measurement was performed on normal VA and defocus-induced VA to 6/18, 6/30, and 6/60 values, using small and large-sized checkerboard stimuli. Prolonged latency and decreased amplitude were found in male and female subject groups, corresponding with decreasing VA levels. Using 18 min arc and 48 min arc-sized checkerboards gave the closest result to the reference value. The difference in VEP value according to subjects' gender was found in amplitude but not in latency.

To study visual evoked potential in patients with optic nerve diseases

Background: To study Visual Evoked Potential in patients with Optic Nerve diseases. Study design and settings: Cross – Sectional study. Material and Methods: 72 patients were included in our study, aged 12 years and above, diagnosed as optic nerve diseases like optic neuritis, Nonarteritc ischemic optic neuropathy (NAION), hereditary, nutritional and compressive optic neuropathy etc. Flash and Pattern VEPs were used. VEP amplitude and latency were noted. Results: Out of total 144 eyes, 107 eyes were affected. Ethambutol induced Toxic optic neuropathy was the most common etiology, followed by secondary optic neuropathy, idiopathic, traumatic optic neuropathy, optic neuritis, NAION, compressive and post CRAO (Central Retinal Artery Occlusion) optic neuropathy. Mean latency of all affected eyes was 132±22.5 msec. mean amplitude of the all affected eyes was 6.36±2.1 microvolt. Latency was moderately delayed (110-140 msec) in 45.8%, while severely delayed (>140 msec) in 40.3% of total eyes. Amplitude was reduced in 36.5% of total eyes. Prolonged latency with normal amplitude was found in most of the eyes with optic neuritis while latency was also prolonged in fellow eyes of optic neuritis. In case of NAION prolonged latency and reduced amplitude was found in all eyes. Conclusion: Flash or pattern VEP can be used as an important tool for diagnosis of optic neuropathies or revealing of recurrence of disease and for follow up. VEP can also be used to detect subclinical damage in the fellow eyes of optic neuritis and also useful in differentiating the optic neuritis from ischemic optic neuropathy.

Bexarotene leads to durable improvements in visual evoked potential latency: A follow-up study of the Cambridge Centre for Myelin Repair One trial

The Cambridge Centre for Myelin Repair One (CCMR-One) trial showed that 6 months of bexarotene reduces visual evoked potential (VEP) latency in people with relapsing-remitting multiple sclerosis (MS). In a single-centre follow-up study of these participants, we re-examined full-field VEP and clinical assessments. Twenty participants (12 bexarotene and 8 placebo) were seen on average 27 months after their trial involvement. In an analysis of all eyes with recordable signal (24 bexarotene and 14 placebo), the adjusted bexarotene-placebo treatment difference in P100 latency was −7.79 (95% confidence interval (CI) = −14.76, −0.82) ms, p = 0.044. We conclude that there were durable improvements in VEP latency, suggesting long-term benefits from exposure to a remyelinating drug.

Knocking out the LRRK2 gene increases sensitivity to wavelength information in rats

Leucine-rich repeat kinase 2 (LRRK2) is a gene related to familial Parkinson’s disease (PD). It has been associated with nonmotor symptoms such as disturbances in the visual system affecting colour discrimination and contrast sensitivity. This study examined how deficiency of LRRK2 impacts visual processing in adult rats. Additionally, we investigated whether these changes can be modelled in wild-type rats by administering the LRRK2 inhibitor PFE360. Visual evoked potentials (VEPs) and steady-state visual evoked potentials (SSVEPs) were recorded in the visual cortex and superior colliculus of female LRRK2-knockout and wild-type rats to study how the innate absence of LRRK2 changes visual processing. Exposing the animals to stimulation at five different wavelengths revealed an interaction between genotype and the response to stimulation at different wavelengths. Differences in VEP amplitudes and latencies were robust and barely impacted by the presence of the LRRK2 inhibitor PFE360, suggesting a developmental effect. Taken together, these results indicate that alterations in visual processing were related to developmental deficiency of LRRK2 and not acute deficiency of LRRK2, indicating a role of LRRK2 in the functional development of the visual system and synaptic transmission.

Investigation of optic nerve function in Behçet's patients with optic disc hyperfluorescence in fundus fluorescein angiography.

The aim was to investigate the changes in optic nerve function that may help in the diagnosis of subclinical optic nerve involvement in patients with Behçet's disease (BD) and isolated optic disc (OD) hyperfluorescence in fluorescein angiography (FA). Three groups were formed; BD patients with isolated OD hyperfluorescence in FA, BD patients without ocular involvement (normal FA) and control group. A total of 88 eyes of 45 patients were included. The groups were compared in terms of OCT-RNFL, contrast sensitivity and VEP latency. When the OCT-RNFL values were compared, there was a significant difference between the control group and Behçet's patients with normal FA. Contrast sensitivity values differed significantly among the groups, and the lowest mean contrast sensitivity was observed in the group with OD hyperfluorescence (p < 0.05). As far as we know, this is the first publication that investigates optic nerve function in BD patients with isolated OD hyperfluorescence in FA. Assessment with FA of asymptomatic BD patients with visual complaints and low contrast sensitivity may be helpful at early detection of inflammatory optic neuropathy by close follow-up in patients with OD hyperfluorescence.

The Effect of Ethambutol Therapy in terms of Visual Evoked Potential, Color Vision Test, and Contrast Sensitivity Test at the Subclinical Level

Abstract&#x0D; Introduction &amp; Objectives : Ethambutol is one of the first-line drugs in the treatment of tuberculosis and known to induce optic neuropathy. However, there are unknown protocols for detecting subclinical level of toxicity. The aim of this study was to assess the difference in amplitude and latency of visual evoked potential (VEP), color vision, and contrast sensitivity in tuberculosis patients before and after taking ethambutol for 1 and 2 months.&#x0D; Methods : This was a prospective observational cohort study of 38 eyes of 19 newly diagnosed patients with category-1 tuberculosis being treated with ethambutol. All patients were given ethambutol for 2 months at a dose of 15 - 20 mg/kg body weight/day. The participants underwent complete eye and visual function examination including pattern-reversal VEP, color vision with Farnsworth Munsell D-15 test, and contrast sensitivity with LEA Low Contrast Flip Chart before and after 1 and 2 months of treatment. Wilcoxon test was employed for data analysis.&#x0D; Results : During the study, no changes in visual acuity was observed. The results showed that the latencies of VEP after 1 month (p = 0.000) and 2 months (p = 0.000) of treatment were significantly delayed. There was a significant difference in contrast sensitivity after 2 months (p = 0.014) of treatment. However, no significant difference was found in color vision and amplitude of VEP.&#x0D; Conclusion : Latency of VEP and contrast sensitivity test could prove useful in detecting subclinical and hence very useful for monitoring patients under ethambutol therapy for ocular toxicity.

Evoked potentials after autologous hematopoietic stem cell transplantation for multiple sclerosis

ObjectiveTo investigate the effect of autologous hematopoietic stem cell transplantation (AHSCT) on functional aspects of the nervous system assessed by visual (VEP), somatosensory (SEP), and motor (MEP) evoked potentials in patients with relapsing-remitting multiple sclerosis. BackgroundSeveral studies have demonstrated the efficacy of AHSCT on inflammatory activity and disability progression in patients with multiple sclerosis. However, the impact of AHSCT on evoked potentials has not been evaluated before. MethodsTwelve AHSCT-treated patients from Uppsala University Hospital were consecutively recruited. Evoked potentials (EP) were collected at baseline and two follow-up visits, 3 and 12 months post-AHSCT. We calculated a composite EP score for each participant and compared it between different time points. ResultsThe median total EP score decreased from 5 at baseline, to 2.5 at 12 months post-ASHCT (p = 0.008). A significant improvement in tibial SEP (tSEP) latencies was observed (42.7 vs 41.5 ms, p < 0.001), with a similar trend for MEP latencies 12 months post-ASHCT. No significant changes in median SEP or VEP latencies were observed. ConclusionsTreatment with AHSCT was associated with improved transmission in some central nervous system pathways in multiple sclerosis patients.

Changes in visual evoked potentials during the menstrual cycle in young women

Background: The visual evoked potential (VEP) is a form of an electrical signal. VEP originates from the visual cortex which is located in Brodman areas 17 and 18 of the occipital lobe. VEP is generated in response to stimulation of the retina by light flashes or pattern stimuli. The advent of VEPs in the 1970s first allowed clinicians to assess neural conduction in the optic nerve. There are many factors that affect VEP such as age and gender; one among them is the hormonal factor. Ovarian and thyroid hormones are vital factors in the generation of olfactory, taste, visual, and auditory neuronal activity. The ovarian hormones progesterone and estrogen play a major role in the conduction of the optic nerve. Aims and Objectives: The aims and objectives of the study are to evaluate the influence of ovarian hormones in the VEPs. Materials and Methods: Among the 1st year medical students, 26 young females (18–20 years of age) were randomly selected. Informed consent was obtained from them and the institutional ethical committee approved the study. Students having regular menstrual periods for the past 6 months with normal visual acuity were included. Those with a history of polycystic ovarian disease, having irregular periods, under hormonal treatment were excluded from the study. Detailed history helps in identifying the proliferative and secretory phases of the menstrual cycle. The P100 wave latency of VEPs was recorded during these two different phases. Results: An unpaired t-test was used for analyzing the data. While comparing the proliferative and secretory phases, P100 wave latency was significantly reduced in the proliferative phase (101±3.6 vs. 97.9 ± 1.43 ms; P &lt; 0.0001). Conclusion: The receptor sensitivity in the visual pathways to dopamine is increased by estrogen which in turn leads to a decrease in the time taken by the visual impulses to reach the visual cortex. Progesterone antagonizes estrogen activity in the central nervous system. Therefore, estrogen is responsible for the reduction in latency during the proliferative phase and progesterone is responsible for the prolonged VEP latency in the secretory phase. Thus, the excitability of the visual system is influenced by the ovarian hormones.

Combination among VEP, OCT and TCD data in patients with relapsing-remitting multiple sclerosis during attack-free period

Aims Multiple sclerosis (MS) is characterized by inflammation, demyelination, glial cell pathology and axonal injury in the central nervous system, and also progressive axonal loss of the optic nerve in cases with optic neuritis (ON). The previous transcranial Doppler (TCD) investigations suggest cortical hyperreactivity in patients with relapsing-remitting Multiple sclerosis (RRMS). We investigated the effect of ON involvement on visual reactivity. Material and methods One hundred thirty patients with RRMS during attack-free period and 12 healthy subjects were enrolled to the study. Visual evoked potential (VEP), optic coherence tomography (OCT) and TCD examinations of all subjects were performed. Results Cerebrovascular reactivity measured with breath holding (BH) test was found to be normal. VEP amplitude, visual reactivity and peripapillary retinal nerve fibre layer (pRNFL) measurements were found to be low in patients with ON involvement, whereas VEP latencies were long. Visual reactivity was negatively correlated with VEP amplitude and RFNL measurements, and positively correlated with VEP latency. Conclusions The present study supports that cerebrovascular reactivity is preserved in patients with RRMS except for attacks, and neurovascular reactivity is increased in patients without ON involvement.

Simultaneous Dry and Gel-Based High-Density Electroencephalography Recordings.

Evaluations of new dry, high-density EEG caps have only been performed so far with serial measurements and not with simultaneous (parallel) measurements. For a first comparison of gel-based and dry electrode performance in simultaneous high-density EEG measurements, we developed a new EEG cap comprising 64 gel-based and 64 dry electrodes and performed simultaneous measurements on ten volunteers. We analyzed electrode-skin impedances, resting state EEG, triggered eye blinks, and visual evoked potentials (VEPs). To overcome the issue of different electrode positions in the comparison of simultaneous measurements, we performed spatial frequency analysis of the simultaneously measured EEGs using spatial harmonic analysis (SPHARA). The impedances were 516 ± 429 kOhm (mean ± std) for the dry electrodes and 14 ± 8 kOhm for the gel-based electrodes. For the dry EEG electrodes, we obtained a channel reliability of 77%. We observed no differences between dry and gel-based recordings for the alpha peak frequency and the alpha power amplitude, as well as for the VEP peak amplitudes and latencies. For the VEP, the RMSD and the correlation coefficient between the gel-based and dry recordings were 1.7 ± 0.7 μV and 0.97 ± 0.03, respectively. We observed no differences in the cumulative power distributions of the spatial frequency components for the N75 and P100 VEP peaks. The differences for the N145 VEP peak were attributed to the different noise characteristics of gel-based and dry recordings. In conclusion, we provide evidence for the equivalence of simultaneous dry and gel-based high-density EEG measurements.

Exaggerated response to pattern reversal visual evoked potential among migraineurs

Objective Visual evoked potential recording has reported ambiguous results among migraineurs, thus the present study explored the association of check-size and reversal rates on the latency and amplitude of pattern reversal VEP among migraineurs. Method and material Monocular VEP responses for both eyes were recorded in 133 migraineurs and 111 controls. Checkerboard pattern with phase reversal frequency of 0.5, 1, 2 and 4 Hz and check-size of 16 × 16, 32 × 32, 64 × 64 and 128 × 128, i.e. spatial frequency of 0.475, 1.029, 2.056 and 4.112 cycle per degree (cpd) were used to record 100 responses each. Three-minutes gap was given after change of reversal frequency to a higher rate for next cycle of 4 check-size records. Result A linear increase in latencies was observed with decreasing check-size in both groups, but migraineurs had significantly higher latencies at a given reversal rate. Amplitudes A1 and A2 were higher among migraineurs and amplitude A2 showed an inverted ‘U’ shaped trend with maximum amplitude at 32 × 32 check size (1.029 cpd) in both groups, with an exaggerated response among migraineurs. Check-size 32 × 32 i.e. spatial frequency of 1.029 behaves differently than other larger or smaller check-sizes. Conclusion Variable VEP response for different visual stimuli may be due to differential activation of respective retinocortical pathways and cortical areas. The highest amplitude at modest check-size suggests a contributory role of foveal-parafoveal fibres in migraineurs. Exaggerated physiological response to visual stimuli may be responsible for higher amplitudes and prolonged latencies among migraineurs.

The effect of different blood groups on visual evoked potentials

Introduction and aim. Purpose of the study is to determine whether it is required to use different standards when evaluating visual evoked potential (VEP) measurements of healthy individuals with different blood groups. Material and methods. The study consisted of healthy individuals with different blood groups who have applied to the ophthalmology and neurology outpatient clinic of Düzce University Medical Faculty from January to December 2022. The patients went through detailed ophthalmologic examination and VEP test and only the ones with normal results were included to the study. Results. The study consisted of 119 individuals, with a blood group distribution of 30 A, 29 B, 30 AB and 30 O. VEP latency and amplitude changes were compared and no significant difference was observed within 4 groups in terms of P100 and N70 latency and amplitudes. There was N70 latency prolongation in Rh- group and this difference was found to be statistically significant (p=0.009). Rh+ group was found to be high in terms of P100 amplitudes and this was considered statistically significant (both p=0.023). Conclusion. There was no statistically significant difference in the VEP parameters of the individuals with the ABO blood groups hence same VEP normal values can be used for ABO blood groups.

Electrophysiological and Histological Correlations of Optic Neuritis in the Dark Agouti Rat Model of Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of Inflammatory central nervous system (CNS) disease. Dark agouti (DA) rats immunized with full-length myelin oligodendrocyte glycoprotein (MOG1-125) typically develop a relapsing-remitting EAE form characterized by predominant demyelinating involvement of the spinal cord and optic nerve. Visually evoked potentials (VEP) are a useful objective tool to assess the optic nerve function and monitor electrophysiological changes in optic neuritis (ON). The current study aimed to assess the VEP changes in MOG-EAE DA rats using a minimally invasive recording device and to correlate them with histological findings. Twelve MOG-EAE DA rats and four controls underwent VEP recording at day 0, 7, 14, 21, and 28 post-EAE induction. Tissue samples were obtained on days 14, 21, and 28 from two EAE rats and one control. The median VEP latencies were significantly higher on days 14, 21, and 28 compared to baseline, with maximal latencies observed on day 21. The histological analyses on day 14 demonstrated inflammation with largely preserved myelin and axonal structures. Inflammation and demyelination with largely preserved axons were evident on days 21 and 28, which correlated with prolonged VEP latencies. These findings suggest that VEPs may be a reliable biomarker reflecting the optic nerve involvement in EAE. Moreover, the use of a minimally invasive device enables observation of VEP changes over time in MOG-EAE DA rats. Our findings may have important implications for testing the potential neuroprotective and regenerative effects of new therapies for CNS demyelinating diseases.

Effects of Smoking on Pattern Visual Evoked Potentials

Aim: The aim of the study is to get a better understanding of the side effects of smoking by evaluating the effect of recently elevated smoking rate on Visual Evoked Potentials (VEP) and to determine whether it is necessary to use different normals when evaluating the VEP measurements of smoking patients. Material and Methods: The patients who have applied to our ophthalmology and neurology outpatient clinics during 2021-2022 are included to the study. Detailed ophthalmologic examination of the patients as well as their VEP test is completed followed by a dilated fundus examination assessment. The patients with normal results are included to the study. The smoking rate is calculated on pack/year basis. Pattern VEP (PVEP) recording is performed based on Keypoint (Dantec, Denmark) and International Society for Clinical Electrophysiology of Vision (ISCEV) criteria. Data obtained through the study are analyzed by SPSS 21.0 version software. Countable variables with normal distribution between two independent groups are analyzed with Independent Sample T test whereas variables without normal distribution are analyzed with Mann Whitney U test. Chi-square test is used for comparing categorical variables. Results: 71 patients were included to the study where 33 of them were placed in smoking group and 38 in non-smoking group (control group). Smoking group had a yearly cigarette package consumption of 5.20±8.93 (0.2-40). VEP latency and amplitude changes were compared and according to the obtained results; there was P100 latency prolongation in between left and right eye of the patients in the control group and smoking group but it did not have any statistical significance (p=0.910 and p=0.697 respectively). There was no statistically significant difference in either left nor right eye in terms of smoking and P100 and N70 latencies (p=0.707, p=0.838, p=0.717 and p=0.621 respectively). Similarly, there was no significant correlation between yearly package consumption and P100 and N70 latencies and amplitudes of left and right eyes (p=0.503, p=0.410, p=0.776 and p=0.940 respectively). Conclusion: No significant effect of smoking is found on VEP values thus leading us to believe that the same normal intervals can be used in the evaluation of VEP results of both smoking and non-smoking patients.

MWF of the corpus callosum is a robust measure of remyelination: Results from the ReBUILD trial

Myelin repair is an unrealized therapeutic goal in the treatment of multiple sclerosis (MS). Uncertainty remains about the optimal techniques for assessing therapeutic efficacy and imaging biomarkers are required to measure and corroborate myelin restoration. We analyzed myelin water fraction imaging from ReBUILD, a double-blind, randomized placebo-controlled (delayed treatment) remyelination trial, that showed a significant reduction in VEP latency in patients with MS. We focused on brain regions rich in myelin. Fifty MS subjects in two arms underwent 3T MRI at baseline and months 3 and 5. Half of the cohort was randomly assigned to receive treatment from baseline through 3mo, whereas the other half received treatment from 3mo to 5mo post-baseline. We computed myelin water fraction changes occurring in normal-appearing white matter of corpus callosum, optic radiations, and corticospinal tracts. An increase in myelin water fraction was documented in the normal-appearing white matter of the corpus callosum, in correspondence with the administration of the remyelinating treatment clemastine. This study provides direct, biologically validated imaging-based evidence of medically induced myelin repair. Moreover, our work strongly suggests that significant myelin repair occurs outside of lesions. We therefore propose myelin water fraction within the normal-appearing white matter of the corpus callosum as a biomarker for clinical trials looking at remyelination.

Amplitude and latency of visual evoked potential are un-correlated variables: A revelation from normative laboratory database of eastern India

To establish normative database andinvestigate whether VEP amplitude and latency have any correlation between them. Institution based cross-sectional observational study done in Electrophysiology of Vision Laboratory at a tertiary centre in Eastern India. 126 subjects of age group between 20 and 59 years of either sex with best corrected visual acuity 6/6 in both eyes and no other eye ailments (except error of refraction) on examination with informed consent were included. PVEP with pattern reversal stimulus with check element size 1° (60') was recorded with Retimax “Advanced” machine (manufactured by CSO s.r.l., (Firenze) Italy) and standard silver-silver chloride disc electrodes. The test parameters were customized in the machine by the manufacturer and designated to measure the N75-P100 amplitude and P100 latency.Normative values were established for our laboratory. Only the most reliable parameters for clinically significant alterations of visual pathway i.e. N75-P100 amplitude and P100 latency were included in the analysis. Results of uniocular, age group-wise and gender-wise values were obtained by descriptive statistics as per ISCEV guidelines. No linear co-relationship (ascertained by Spearman's rho Correlation Coefficient) was found between N75-P100 amplitude and P100 latency, in either of the eyes. PVEP amplitude and latency are uncorrelated variables. To the best of our knowledge, our study was the first study in literature on correlation between amplitude and latency of PVEP.