Changes In Visual Evoked Potentials Research Articles

Intraoperative monitoring of visual evoked potentials: experience of 240 operations

Background. Intraoperative monitoring (IOM) of visual evoked potentials (VEPs) is used to inform surgeons about impacts on the visual system in order to prevent iatrogenic visual impairment. The VEP monitoring use become widespread only in the last decade; nowadays, there is no generally accepted methodology for its implementation, and the effectiveness of VEP monitoring and the factors determining it have not been sufficiently studied.Aim. The aim of the study was to investigate the factors influencing the VEP monitoring feasibility and effectiveness.Materials and methods. Data from 240 consecutive neurosurgical operations performed using VEP monitoring were retrospectively reviewed. IOM data (registration parameters, presence and type of VEP changes), patient characteristics (gender and age, tumor type and location, presence of preoperative visual dysfunctions), anesthesia parameters and postoperative changes in vision were studied. Statistical analysis was performed using χ2 and Mann–Whitney tests.Results. VEPs were obtained in 91.3 % of eyes with completely or partially preserved vision. The main factors reducing the chances to record VEPs successfully are preoperative visual disorders and the use of inhalation anesthesia. A personalized approach to the selection of reference electrodes and frequency filtering parameters makes it possible to reduce the number of averagings required for VEP recording and accelerate informing surgeons. With successful monitoring 59.1 % of eyes had no noticeable VEP changes; 5.8 % of eyes had signs of intraoperative improvement; 35.1 % had signs of deterioration. Among the last category, 60.7 % of eyes had full VEPs recovery afterwards. After surgery, new visual disorders were detected in 2.6 % of eyes without signs of intraoperative deterioration, in 6.7 % – with temporary deterioration, and in 19.3 % – with signs of deterioration persisted until IOM is finished. Assessing the sensitivity and specificity of VEP monitoring is hampered by the possibility of complications in the early postoperative period and IOM influence on the course and results of the operation. The proportion of total resections was maximal when VEP monitoring was successful. In the subgroup without preoperative visual impairments, the alarms during monitoring were associated with decrease in proportion of total resections proportion due to increase in proportion of subtotal resections.Conclusion. VEP monitoring with a personalized approach allows effective monitoring of visual functions preservation during neurosurgical operations.

Visual evoked potential in generalized joint hypermobility: A case-control study.

Generalized joint hypermobility (GJH) can be the result of several hereditary connective tissue disorders, especially Ehlers-Danlos syndrome. Cerebrovascular manifestations are among the most common complications in this disorder, and understanding their extent can help better diagnosis and prevention of hazardous events. We investigated visual evoked potential (VEP) changes in patients with GJH and compared them with healthy individuals. Our case-control study included 90 patients who fulfilled the Beighton score (B score) for joint hypermobility and other 90 healthy participants. All of them went under VEP study, and the amplitude and latency of the evoked potential (P100) were compared to each other. The Case group had significantly higher B score (7.18±0.967 vs. 1.18±0.712), P100 latency (110.23±6.64ms vs. 100.18±4.273ms), and amplitude (6.54±1.26mv vs. 6.50±1.29mv) compared with the Control group, but the difference was only significant regarding B score, and P100 latency (p-value <.0001). Moreover, both latency and amplitude of P100 had significantly positive correlations with the B score in the Case group (p-value <.0001), but such correlations were not found in the Control group (p-value=.059). Our study could reveal VEP changes, especially significant P100 latency in GJH patients without previous neurologic or musculoskeletal disorders. Whether these changes are due to GJH itself or are predictive of inevitable neurologic disease or visual pathway involvement, particularly Multiple Sclerosis needs further investigation with longer follow-up periods.

Utility of Visual Evoked Potentials (VEPs) study in the evaluation of visual pathway dysfunction in diabetics without retinopathy: correlations with diabetic peripheral neuropathy and other clinical findings.

Aim and objectives: Visual dysfunction in diabetes mellitus (DM) is multifactorial and can be due to vascular disease, and metabolic abnormalities that can affect the retina, optic nerve, and visual pathways. Visual evoked potential (VEP) is an electrophysiological test that can quantify the functional integrity of the visual pathways from the retina via the optic nerves, and optic tracts to the visual cortices. In this study, we aimed to investigate the visual pathway dysfunction among diabetics without retinopathy compared with healthy controls and to look for any correlation with diabetic neuropathy, duration of diabetes, or HbA1c level. Methods: The study included 75 diabetic patients and 75 age and sex-matched controls. VEPs were recorded using the pattern reversal stimulation method on the Medtronic EMG EP machine, and P100 latency and N75-P100 amplitude were recorded in both diabetic patients and healthy controls. Results: Mean P100 latency was significantly prolonged and N75-P100 amplitude significantly reduced among diabetic cases compared to healthy controls (p < 0.001). Among diabetics with peripheral neuropathy, P100 latency was significantly prolonged and N75-P100 amplitude was significantly reduced compared to diabetics without peripheral neuropathy. A significant positive correlation of VEP P100 latency (p < 0.001) and a negative correlation with N75-P100 amplitude (p < 0.001) with duration of disease were also found. Conclusion: VEP changes are observed in diabetics before the development of retinopathy or peripheral neuropathy indicating optic pathway dysfunction, which precedes the development of these complications. Early preclinical visual pathway dysfunction can warrant taking the necessary measures to reduce diabetic complications. Abbreviations: DM = Diabetes Mellitus, VEP = Visual Evoked Potential, HbA1c = Hemoglobin A1 c, MRI = Magnetic Resonance Imaging, EEG = Electroencephalography, P100 = Positive wave peak at latency 100 ms (millisecond), N75 = Negative wave peak at latency 75 ms (millisecond), N145 = Negative wave peak at latency 145 ms (millisecond), OCT = Optical coherence tomography, PRVEP = Pattern Reversal Visual Evoked Potential, NCS = Nerve Conduction Study, SSR = Sympathetic Skin Response, IL1 = Interleukin-1, LIF = Leukemia inhibitory factor, CNTF = Ciliary neurotrophic factor, TNF alpha = Tumor necrosis factor-alpha, TGF-beta = Transforming growth factor-beta.

Electrophysiological study of visual processing in children with cochlear implants

Electrophysiological studies of congenitally deaf children and adults have reported atypical visual evoked potentials (VEPs) which have been associated with both behavioral enhancements of visual attention as well as poorer performance and outcomes in tests of spoken language speech processing. This pattern has often been interpreted as a maladaptive consequence of early auditory deprivation, whereby a remapping of auditory cortex by the visual system ultimately reduces resources necessary for optimal rehabilitative outcomes of spoken language acquisition and use. Making use of a novel electrophysiological paradigm, we compare VEPs in children with severe to profound congenital deafness who received a cochlear implant(s) prior to 31 months (n = 28) and typically developing age matched controls (n = 28). We observe amplitude enhancements and in some cases latency differences in occipitally expressed P1 and N1 VEP components in CI-using children as well as an early frontal negativity, N1a. We relate these findings to developmental factors such as chronological age and spoken language understanding. We further evaluate whether VEPs are additionally modulated by auditory stimulation. Collectively, these data provide a means to examine the extent to which atypical VEPs are consistent with prior accounts of maladaptive cross-modal plasticity. Our results support a view that VEP changes reflect alterations to visual-sensory attention and saliency mechanisms rather than a re-mapping of auditory cortex. The present data suggests that early auditory deprivation may have temporally prolonged effects on visual system processing even after activation and use of cochlear implant.

Poster Session I: Noninvasive neuromodulation of subcortical visual pathways with transcranial focused ultrasound.

Transcranial ultrasound stimulation (TUS) is an emerging tool to noninvasively modulate neural activity in deep brain areas. In preparation for our first in-human TUS studies, we targeted TUS to the lateral geniculate nucleus (visual thalamus) in a large mammal (sheep). Full-field light flash stimuli were presented with or without concomitant TUS in randomly interleaved trials. Similar to what has previously observed by Fry et al (Nature 1959) in cats, EEG visual-evoked potentials (VEPs) were reversibly suppressed by TUS to the LGN. No changes in VEPs were observed in sheep who received sham-TUS to a control site in the basal ganglia, ruling out potential transducer auditory-somatosensory confounds. Magnetic resonance acoustic radiation force imaging (MR-ARFI), a technique to measure the ultrasound focus in situ, showed a focal volume of microscopic displacement at the expected target. Excitingly, MR-ARFI predicted the suppressive effect on VEPs in individual subjects, suggesting that MR-ARFI can be used to confirm TUS targeting and estimate neurophysiological impact. We are now translating this paradigm into human, targeting TUS to the LGN while participants perform a contrast detection task with EEG recording of steady-state VEPs. MR-ARFI will be measured to evaluate targeting and estimate TUS dosage in each participant. This work provides the foundation for a dissection of the roles of different subcortical nuclei in different aspects of human vision.

Assessment of Visual Evoked Potential to Detect Visual Pathway Dysfunction in Gestational Diabetes Mellitus: A Longitudinal Case-Control Study With Postpartum Follow-up.

The increasing prevalence of gestational diabetes mellitus (GDM) during pregnancy has opened the opportunity to study its short- and long-term effects on maternal ophthalmic health. Visual evoked potential (VEP) is a non-invasive electrophysiological test that detects functional disturbances along the visual pathway before the physical signs of diabetic retinopathy (DR) can set in.This longitudinal study is aimed at the assessment of changes in VEP in GDM during different stages of pregnancy and 6-12 weeks after parturition by comparing it with normoglycemic controls. Diagnosed cases of GDM were recruited along with normoglycemic controls at 24-28 weeks of gestation.Each participant was required to attend two follow-up appointments at 32-38 weeks of gestation and 6-12 weeks after parturition. A blood sample was taken in a fasting state to record biochemical parameters. VEP was recorded using Neuropack S1 MEB-9400 electrodiagnostic equipment (Nihon Kohden, Tokyo, Japan) in a dark room by providing pattern reversal stimuli to each eye. A total of 29 participants (15 in the control group and 14 in the GDM group) completed the entire study procedure.The observed mean P100 latency of both eyes in the GDM group was recorded longer as compared to that in the control group at baseline and during late pregnancy. Although the mean P100 latency saw a significant decline in postpartum visits as compared to that in late pregnancy, the values were higher than in the control group. P100 latency at baseline correlated significantly to serum advanced glycated end products' (AGE'S) levels in the GDM group. Our study findings reflect that the diagnosis of GDM is associated with significant changes in VEP during and after pregnancy as compared to that of healthy pregnant women.

Влияние мультифокальных ИОл на электрофизиологические параметры зрительного анализатора

The study of the electrophysiological parameters of the organ of vision before and after the implantation of multifocal intraocular lenses (mfIols) would provide new information about the effect of this type of lens on the processes of excitability and conduction of various parts of the visual analyzer as elements of the neuroadaptation process. Purpose of this study was to test the hypothesis about the effect of mfIol on the electrophysiological parameters of the organ of vision in the process of neuroadaptation of the central nervous system. Material and methods. The design is a prospective selective study. the total number of study participants was 48 patients. the object of the study were patients with a diagnosis of cataract. all patients underwent cataract surgery with mfIol implantation in one eye. the operation on the second eye was performed a month later. registration of visual evoked potentials (VEp) and electroretinography (Erg) were performed using the diopsys® noVa™ system. the diopsys® pErg-24 protocol was used to evaluate Erg. Functional Erg was also investigated using the diopsys® ffErg/Flash plus phnr protocol. VEp was assessed using the diopsys® VEp User-defined visual evoked potential protocol using 32×32 and 64×64 checkerboard pattern stimuli at low and high contrast levels. the number of analyzed features was — 122 units. Examination was carried out immediately before the first operation, the next day after the operation on the first eye, 1 month later (before and after the operation on the second eye), and after 3 months of observation. Results. Based on the results of the study, a quantitative characteristic was given to all evaluated features. the dynamics of indicators has been established. Significant differences were noted in some indicators, which may indicate the effect of the implanted mfIol on the electrophysiological parameters of the visual analyzer, indicating the presence of neuroadaptation process. Conclusion. 1. Implanted mfIols do not affect the function of ganglion cells and their axons. 2. the established changes in VEp are nonspecific, but the results obtained are statistically significant, which may indicate the effect of the implanted mfIol on the electrophysiological parameters of the visual analyzer. Keywords: neuroadaptation, electrophysiology of the organ of vision, multifocal intraocular lenses, cataract

Особливості зміни фонової енцефалограми у відповідь на функціональні навантаження у хворих на дисбінокулярну амбліопію залежно від фіксації амбліопічного ока

Background: Analysis of electroencephalogram (EEG) visual-evoked potentials (VEPs) is important for assessing the general integrity of the visual pathway. Pathology in any portion of the visual pathway causes changes in VEP. Percentages of alpha, beta, delta and theta rhythms in the EEG record, frequencies and amplitudes of these waves, and the level of alpha-rhythm suppression are essential for characterizing the state of the visual system. Purpose: To indentify the features of the state of the visual system and changes in the background EEG in response to activation procedures in strabismic amblyopes depending on type of fixation in the amblyopic eye. Material and Methods: Fifty-two strabismic amblyopic patients aged 5-8 years and 15 healthy children of the same age underwent an examination. Of the amblyopic children, 32 had unilateral amblyopia with esotropia (6-15 degrees). Of these 32 children, 20 had eccentric fixation and 12 children, central fixation. The 10–20 system of electrode placement was employed to perform EEG in all children. Rhythms of the background EEG, interhemispheric asymmetry and alpha, theta and delta wave percentages were assessed. Brain potentials were recorded using standard activation procedures to activate deep brain structures. Results: Alpha rhythm was not discernable in the background EEG in the occipital areas in 3.0 ± 2.6 % of cases, and the alpha index was below the normal range in 48.6 ± 8.2 % of patients with a visual acuity worse than 0.3. Delta index was above the normal range (25%-45%) in 48.6 ± 8.2 %, and theta index was above the normal range (with a mean value of 48.4 ± 8.2 %) in 48.6 ± 8.2 % of children. Reduced percentage of alpha activity was found in almost half of strabismic amblyopic children, indicating immaturity of the synchronizing system and impaired oculomotor tuning in the eyes of these children. Abnormal bilateral EEG response to eye-opening stimulation and abnormal bilateral EEG rhythmic driving response (RDR) were seen in most children with eccentric fixation, but not in most children with central fixation. Photic stimulation in strabismic amblyopic children resulted in bilaterally asymmetrical and synchronous theta and delta waves in symmetric frontal (theta and delta percent time of 46.0 ± 8.4%) and occipital (theta and delta percent time of 50.0 ± 8.4%) responses. Conclusion: Increased theta and delta wave percentages in frontal and occipital derivations were found in strabysmic amblyopes (irrespective of type of fixation in the amblyopic eye) compared to healthy controls. Abnormal EEG response to eye opening and abnormal EEG RDR were found in strabysmic amblyopes. This indicates the presence of functional changes in the midline brain structures including the corpus callosum, which impedes the development of binocular vision in strabismic amblyopes.

Can Serum Magnesium Level and Visual Evoked Potentials (P100) be a Predictive in Migraineurs?: Evidence Based Study.

Few dating back, the role of visual evoked potentials changes and reduced level of intracellular magnesium have appeared in migraine patients both throughout the attacks and in the interictal periods. Moreover, there is a lack of evidence regarding the correlation between magnesium levels and visual evoked potentials. To assess the changes in the levels of magnesium in migraineurs compared to a healthy control group is our prime intention. Also, to correlate serum magnesium levels with visual evoked potentials changes within the migraineurs is a secondary part of the study. After applying inclusion and exclusion criteria as per the study protocol, in total, 80 subjects were enrolled in the study. Of which 40 were migraineurs diagnosed as per the International Headache Society criteria for severe migraine headache. Rest of 40 was nonmigraineurs served as a control group of the study. All included patient was submitted to demographic profile, previous history of the disease and drug intake, thorough clinical investigation and baseline laboratory parameters. Apart from this, the measurement of visual evoked potentials changes (4th block) and magnesium levels were done as per our standard operating procedures. In migraineurs, serum total Mg level was considerably lower compared to the control group (1.79 ± 0.14 mg/dl versus 2.10 ± 0.17 mg/dl, P < 0.0001) and amplitude of P100 (P < 0.0001) was negatively correlated to reduced serum Mg level (P < 0.0001). As expected, both elevated visual evoked potential amplitude and reduced level of brain magnesium can be a demonstration of neuronal hyperexcitability of the optic pathways associated with a dropped threshold for migraine attacks.

Neutrophil–lymphocyte ratio as a reliable marker to predict pre-clinical retinopathy among type 2 diabetic patients

BackgroundDiabetic retinopathy is now recognized as a neurovascular in lieu of a microvascular complication. Visual evoked potentials (VEPs) are greatly valuable in detecting early diabetic retinal functional changes before the occurrence of structural damage. Low-grade inflammation plays a fundamental part in the development and progression of retinopathy in diabetics. Detecting diabetic patients with early retinopathy before the occurrence of clinical symptoms provides a window of opportunity to ensure the best prognosis for these eyes. Neutrophil–lymphocyte ratio (NLR) has recently been introduced as a novel marker of inflammation in various diseases. Indeed, the presence of a cheap, available, and reliable marker of inflammation that is capable to detect pre-clinical diabetic retinopathy (P-DR) is crucial for early intervention to retard the progression of ocular damage. As far as we know no previous studies investigated the role of NLR in the detection of P-DR. The aim of this study was to investigate the quality of prediction of NLR in detecting pre-clinical retinopathy in type 2 diabetic patients.ResultsIn this case–control study, VEPs results showed a significant delay in P100 latencies of the patients’ group compared to the control group. According to the VEPs results, the patient group was further subdivided into two: diabetic with VEPs changes (a group with P-DR) and diabetic without VEPs changes. NLR was significantly elevated in patients with P-DR (p < 0.001). NLR cut-off point ≥ 1.97 is able to predict P-DR with 89.29% sensitivity and 84.37% specificity. Linear regression model revealed that NLR is the only independent factor that predicts P-DR. (odds ratio 3.312; 95% confidence interval 1.262–8.696, p = 0.015*.ConclusionsVisual evoked potentials have an important role to evaluate the visual pathway in diabetics and to diagnose pre-clinical diabetic retinopathy before the occurrence of structural damage. Neutrophil–lymphocyte ratio is a reliable marker for the detection of pre-clinical diabetic retinopathy with good sensitivity (89.29%) and specificity (84.37%). Finding a reliable available laboratory test to predict P-DR could be of help to save diabetic patients from serious ocular complications.

A comparative study of visual evoked potential parameters in type 2 diabetes mellitus patients with increasing duration

Background: Type 2 diabetes mellitus (T2DM) is endocrine disorder showing increasing prevalence worldwide. Chronic hyperglycemia of diabetes affects various organs of our body and causes dysfunction and failure of them. Diabetic retinopathy is a grave complication of diabetes mellitus. Diabetes causes neurodegeneration in retina well before the frank retinopathy. Early detection of these changes by visual evoked potentials (VEPs) may prevent the development of this complication in future, so it can be used as a screening test. Aims and Objectives: The study aimed to compare the VEP changes with the duration of T2DM. Materials and Methods: An analytical case–control study was done after obtaining Ethical Committee permission. VEPs were recorded with RMS EMG EP MK II machine. The duration of the diabetes was used to divide patients into two groups: Group I - 30 patients with disease duration &lt;15 years; and Group II - 30 patients with T2DM with disease duration &gt;15 years. Analysis and processing of the data was done by using statistical software SPSS23.0 using t-test. The significance level was taken as P &lt; 0.05. Results: The comparative analysis between groups showed significant prolongation in latencies of P100 wave and N 145 wave in group II and reduced N75 - P100 amplitude in group II, though it was not statistically significant. Conclusion: It is concluded that the visual pathway is affected by diabetes and VEP changes are correlated with its duration. Therefore, VEPs can be used as a prognostic marker.

IMPLEMENTATION OF VISUAL EVOKED POTENTIAL FOR THE DETECTION OF PRERETINOPATHY AND PROGNOSTICATION IN DIABETES MELLITUS

Introduction: Diabetic Retinopathy (DR) is one of the complications of Diabetes Mellitus (DM) which affects the retinal blood vessels. It is one of the preeminent causes of blindness in the age group of 20 to 74 years albeit that visual loss due to it may be preventable by adequate glycaemic control. Visual Evoked Potential (VEP) can be used in diagnosis of retinal changes and ascertainment of prognosis can be done by it. Aim: To evaluate the ability of VEP in identifying preclinical neuro-degenerative changes in patients with diabetic preretinopathy by studying changes in VEP. Materials and Methods: This study comprises of 30 diabetic patients without retinopathy and 30 non diabetic controls. Patients were selected from the outpatient Department of Ophthalmology for the screening of DR. Latency of P100 was analysed because of its reliability and less inter-subject variability. Mean P100 wave latency of both groups were compared and analysis was done regarding any discrepancy in P100 wave latency with respect to the duration and the control of diabetes. Data was analysed using IBM-SPSS 27. Student's t- test was applied when two groups were compared whereas Analysis of Variance test was applied for multiple group comparisons. The p value &lt;0.001 was considered statistically signicant. Results: There was signicant prolongation of P100 latency in diabetics without retinopathy. It was also observed that there was positive correlation between prolongation of P100 latency and duration of diabetes. Conclusion: VEP could be a better tool for the detection of very early retinal changes before any clinical evidence of retinopathy has set in. Adequate glycaemic control, dietary modication, appropriate dosage of medications could prevent the early development of retinopathy if done at this stage

Characteristics and dynamics of pathological changes in visual evoked potentials in multiple sclerosis

Clarification of the characteristics and dynamics of changes in the main indicators of visual evoked potentials (VEP) for a reverse chess pattern in patients with multiple sclerosis (MS) at various stages of the disease and severity of disability. The study of VEP was carried out on 477 subjects, 120 of which were healthy volunteers and 357 patients with MS, including those with clinically isolated syndrome (CIS; 22.7%), remitting course (RT; 55.7%), primary progressive course (PPT; 8.4%), secondary progressive course (VPT; 13.2%). Disability was assessed using the Expanded Disability Status Scale (EDSS). A high sensitivity of VEP in the detection of demyelinating damage to the visual pathways, including subclinical, was noted already at the initial stages of MS, which increases with the progression of the disease from 77.8 to 97.8%. There was a significant increase in latency (r=0.42, p<0.05) and a decrease in amplitude (r= -0.26, p<0.05) of the P100 peak as the EDSS score increased. In patients with MS, 5 patterns of VEP were identified depending on the level and severity of damage to the visual pathways, where pattern 1 is normative VEP, pattern 5 is the absence of VEP recording in case of a pronounced axonal-demyelinating lesion of the visual pathways (prechiasmal/postchiasmal levels). Patterns 1 and 2 are most typical for CIS (22.2 and 53.1%) or RT (20.1 and 26.6%). Patterns 3 and 4 are typical for APT (70 and 20%) and VPT (48.9 and 21.3%), pattern 5 - for VPT (19.1%). Patterns 3-5 predominated in patients with higher EDSS (r=0.54, p<0.05). The classification of VEP changes into patterns makes it possible to identify the dissemination of a focal lesion in the projections of the visual pathways, which increases the diagnostic efficiency of the study and makes it possible to assess the severity of MS.

The impact of cannabis consumption on visual processing

AbstractPurpose: Cannabis is one of the most widely used recreational drug in Canada. The purpose of this study is to evaluate the effect of cannabis consumption on the visual pathway via non‐invasive, objective electrophysiological testing.Methods: Full field electroretinograms (ffERGs) including photopic negative responses (PhNRs), and visual evoked potentials (VEPs) were recorded in non‐users (control group) and in cannabis users. International Society for Clinical Electrophysiology of Vision (ISCEV) standard clinical protocols were used for all exams. Cannabis users were tested twice: at least 12 h after their last cannabis consumption (chronic group) and 2.5 h following their last consumption (acute group).Results: When comparing the chronic and acute groups via paired t‐tests (n = 15), there was a statistically significant decrease in (1) the scotopic a‐wave amplitude (chronic −139.8 ± 7.4 μV and acute −114.8 ± 6.8 μV; p = 0.03; stimulus 10.0), (2) PhNR amplitude (chronic −32.2 ± 4.8 μV and acute −26.6 ± 3.1 μV; P = 0.01; stimulus 7 cd•s/m2), and the amplitude of the following two VEP parameters (3) N75 (chronic −2.6 ± 0.9 μV and acute −2.0 ± 1.1 μV; p = 0.04; stimulus 30 min), and (4) N135 (chronic −15.0 ± 1.4 μV and acute −12.3 ± 1.2 μV; p = 0.03; stimulus 15 min). PhNR implicit time was statistically significantly increased when comparing the control (63.4 ± 1.5 ms; n = 18) and the acute (69.1 ± 1.9 ms; n = 15) group (p = 0.03; stimulus 7 cd•s/m2). There were no statistically significant changes in ffERGs and VEPs between the control and chronic groups.Conclusions: The results of this pilot study suggest that acute use of cannabis temporarily causes a reduction in photoreceptor activity with a downstream decrease in cortical activity. These changes appear to be reversible as there was no difference between the chronic exposure and the control groups.

Memantine administration in patients with optic neuritis: a double blind randomized clinical trial

As an inflammatory phenomenon, optic neuritis (ON) that causes demyelination in the optic nerve damages the retinal cells, and leads to visual impairment. Herein, we aimed to investigate the potential therapeutic effects of memantine on ON. In this double-blinded randomized clinical trial, participants with the first episode of acute ON meeting the inclusion criteria were enrolled and were randomly divided into memantine group (MG; N = 20) and placebo group (PG; N = 18). Patients of MG received memantine for 6 weeks. The thickness of the retinal nerve fiber layer (RNFL), visual evoked potential (VEP), and visual acuity (VA) was measured in both groups at baseline and 3-month follow-up. Thirty-eight patients with ON were enrolled. In the follow-up, mean RNFL thickness of both groups significantly decreased in all quadrants (P < 0.001). Also, RNFL thickness of all but temporal quadrants were significantly higher in the MG than placebo. The reduction in RNFL thickness difference was insignificant between two groups in all but the inferior quadrant which was significantly lower in MG (P = 0.024). In follow-up, mean-to-peak of P100 of the affected eye were significantly lowered (P < 0.001). The changes in VEP were insignificant. Originally, the mean VA was 0.15 ± 0.08 and 0.17 ± 0.09 in MG and PG, respectively, but was improved significantly to 0.92 ± 0.06 and 0.91 ± 0.06 in MG and PG, respectively, in follow-up. Memantine can reduce the RNFL thinning in three quadrants by blocking NMD receptors. However, visual acuity did not show a significant difference between the two groups.

Visual Evoked Potential Findings and Correlation between Visual Evoked Potential and Clinical Severity in Children with Autism Spectrum Disorder

Background: Autism spectrum disorder (ASD) is a heterogeneous behavioral disorder that is characterized by qualitative deficits in social communication and interaction and restricted, repetitive behavioral patterns, activities, and interests. For an optimum outcome in children with autism, early intervention (preferably before three years of age) is essential. Hence, there is a critical need to improve the awareness of ASD to enable earlier detection and intervention. The present study aims at achieving the following: (1) Investigating neural transmission within the visual system using visual evoked potentials (VEPs) as an index of the myelination process of the visual pathway. (2) Correlating the changes in the VEPs with the clinical severity of autism. (3) Investigating the possible gender differences in VEPs in autistic children. Materials and Methods: The study was conducted on 60 preschool children (11 females and 49 males) who were recruited from the autism center and the pediatric neurology ward and who met the DSM-V criteria for autism in the Pediatric Hospital for the period from 12 December 2019 to 1 June 2021. Their mean age was 4.5±1.17 years. Another 50 (40 males and 10 females) age- and gender-matched normally developed children served as the control group. Both groups were subjected to a detailed history, as well as complete physical and neurological examinations. The VEPs were assessed for all of them. The autistic children were excluded from the study if they had any motor, visual impairment, inborn errors of metabolism, epilepsy, other chronic medical or neurological disorders, or if they were taking medications during the period of study. Results: The P100 wave latency of the VEPs was significantly prolonged in both eyes of autistic children as compared with that of the control group. The N75-P100 amplitude was significantly lower in the left but not the right eye of patients when compared with those of normally developed children. Neither the P100 wave latency nor the N75-P100 amplitude of both eyes was associated with the gender or severity of illness. Conclusion: There are distinct changes in VEPs in autistic children, especially the abnormal prolongation of conduction time, suggesting that autistic children may have brainstem and visual pathway dysfunction. Gender and disease severity score have no impact on VEPs.

Diagnostic Impact of Monitoring Visual Evoked Potentials to Prevent Visual Complications During Endovascular Treatment for Intracranial Aneurysm.

IntroductionThe present study aimed to determine the incidence of intraprocedural visual-evoked potential (VEP) changes and to identify correlations with intraprocedural ischemic complications during endovascular treatment in patients with intracranial aneurysm related to visual function.MethodsThis study analyzed data from 104 consecutive patients who underwent endovascular coil embolization to treat intracranial aneurysms related to visual function under VEP and transcranial motor evoked potential (MEP) monitoring. We analyzed associations between significant changes in MEP and VEP, defined as a >50% decrease in amplitude, and both intraprocedural complications and postoperative neurological deficits. Factors associated with postoperative neurological deficits were also assessed.ResultsTreated aneurysms were predominantly located in the internal carotid artery (95%). Five (5%) were located in the posterior cerebral artery (PCA). Significant decreases in intraprocedural VEP occurred in four patients (4%), although one of those four patients did not show concomitant MEP decreases during procedures. Immediate salvage procedures avoided postoperative visual disturbances. All VEP decreases were transient and not associated with postoperative visual impairment. One of three cases who underwent intraoperative balloon occlusion test showed tolerance to balloon occlusion of the proximal PCA under VEP assessment; parent artery occlusion was performed without postoperative visual disturbance in that case.ConclusionAlthough significant VEP decreases occurred 4% during neuro-endovascular aneurysm treatment related to visual function, intraprocedural VEP monitoring identifies ischemic changes associated with visual pathways and facilitates prompt initiation of salvage procedures.

Role of visual evoked potential as a window to detect functional changes that occur without signs of diabetic retinopathy in fundoscopy: Case series involving symptomatic overt diabetic pregnant women

Diabetic retinopathy (DR) is a microvascular complication associated with diabetes mellitus. Pregnancy is a major risk factor for DR in diabetic women. Recent evidenced suggests that in course of DR functional changes including damage of pre-ganglionic and ganglionic cells in retina precede structural microvascular changes. A number of studies in the past have highlighted the role of pattern visual evoked potential (VEP) in detecting such functional changes. However, the study of VEP changes in diabetic pregnancies remains unexplored. This case series has the objective of exploring VEP changes in symptomatic OVD cases, who had no signs of DR on fundoscopy. We present two cases of overt diabetic women who complaint of straining of eyes, headache, and difficulty in reading during pregnancy. Complete ophthalmic examination was done in both the cases followed by a VEP test. VEP test was done as a part of a research project. The ethical clearance for the project was obtained from the Institute’s Ethics Committee before the commencement of the study. Fundoscopic examination in both cases revealed that the retina was within normal limits with no signs of retinopathy. In Case 1, P100 latency was increased for the left eye and was normal for the right eye during the first visit. While P100 latency was increased for both left and right eye during the second visit. There was a substantial increase in P100 latency for both eyes in second visit as compared to first visit. In Case 2, P100 latency was increased for both left and right eye and amplitude decreased for the left eye. This is a case series consisting of symptomatic overt diabetic pregnant women who had increased P100 latency despite no signs of retinopathy in fundoscopy. The previous studies have reported that multiple follow-ups with ophthalmoscopy may not be cost-effective in diabetic pregnant women. VEP provides a window for detection of early functional changes that may help identify at risk patients for follow-up and early intervention.

The predictive value of intraoperative visual evoked potential for visual outcome after extended endoscopic endonasal surgery for adult craniopharyngioma.

Due to the proximity of craniopharyngioma to the optic apparatus, one of the most common complications after surgery is visual deterioration. Intraoperative visual evoked potential (VEP), as a means of real-time visual function monitoring, has been integrated into transsphenoidal surgery for pituitary adenoma to predict postoperative visual outcome. Compared with pituitary tumor, craniopharyngioma often adheres to optic nerves, with increased risk of postoperative visual impairment. Furthermore, extended endoscopic endonasal surgery (EEES) can provide direct visualization of the surgical plane between the craniopharyngioma and the optic nerves, which contributes to analysis of the mechanism of real-time VEP changes during surgery. Therefore, VEP monitoring applied during EEES for craniopharyngioma may have more clinical value. However, only 9 patients who underwent EEES with VEP monitoring for craniopharyngioma have been sporadically reported to date. In this paper, the authors present the largest series to date analyzing the clinical value of VEP to predict postoperative visual outcome in adult patients with craniopharyngioma. Sixty-five adult patients who underwent EEES with intraoperative VEP monitoring for primary craniopharyngioma were retrospectively reviewed. The association between changes in VEP amplitude and postoperative visual outcome was determined. In addition, other potential prognostic factors with regard to postoperative visual outcomes were included in the analysis. Gross-total resection was achieved in 59 patients (90.8%). Reproducible and stable VEP was recorded in 128 of 130 eyes (98.5%). During surgery, VEP remained stable in 108 eyes, 10 (9.3%) of which had new visual acuity (VA) and/or visual field (VF) defects after surgery. Transient VEP decrease was recorded in 15 eyes, 4 (26.7%) of which had visual deterioration. Of the 5 eyes with permanent VEP decrease, 3 (60%) experienced postoperative visual impairment. Permanent VEP decrease (OR 19.868, p = 0.007) and tight adhesion (OR 6.104, p = 0.040) were independent adverse factors for postoperative VA deterioration. Tight adhesion (OR 7.150, p = 0.002) and larger tumor volume (OR 1.066, p = 0.001) were significant risk factors for postoperative VF defects. Intraoperative VEP monitoring can serve as a real-time warning to guide surgeons to avoid postoperative visual impairment. It effectively predicted VA changes in adult patients with craniopharyngioma after EEES. Tight adhesion and larger tumor volume were also strong predictors of postoperative visual impairment.

Electroretinography and visual-evoked potential changes in patients with nystagmus

Background and aim Nystagmus is an ocular motility disorder in which the eyes make uncontrollable, repeated movements. These movements can cause vision and depth perception problems, as well as affect balance and coordination. The aim was to study electrophysiological changes that occur in patients with nystagmus and pattern of changes in each disease. Patients and methods A prospective, institutional, clinical trial was conducted on 60 eyes with nystagmus. The age of the patients ranged between 5 and 50 years, and the patients were chosen from Al-Hassan Eye Center, Giza and Al-Azhar University Hospital outpatient clinic. Results The study revealed the relation between photopic electroretinogram (ERG), scotopic ERG, and flash visual-evoked potential (VEP) and each of fundus examination and final diagnosis of the studied group, and it shows highly statistically significant differences between groups according to fundus examination and final diagnosis. Conclusions Electrophysiological examination is an essential step in the assessment of patients with early-onset nystagmus especially when the eyes are apparently normal on routine examination and should be enrolled within their medical records. This study clarified the need to investigate cases with nystagmus by ERG and suggested that the ERG was useful where the diagnosis was uncertain. Visual-evoked potential is complementary to ERG and can be tested simultaneously.