VEP Changes Research Articles

Visuell evozierte Potenziale bei neurologischen Erkrankungen

Purpose. Light triggers a chemical reaction in the retinal photoreceptors. Electrical signals are transmitted through all neurons of the visual pathway into the visual cortex. Resulting potential fluctuations can be derived as visually evoked po- tentials (VEP) and analyzed regarding latency and amplitude in order to get an indication of pathological changes within the visual pathway. Method. This article shall explain the processes leading to the emergence of potentials in the visual cortex, which methods and techniques of VEP are available and in which neurological diseases a clinical added value for finding a diagnosis is given. Results. In VEP, a response of all neurons is represented, which is mainly generated by central visual field components. In order to be able to represent pathologies, that affect only partial areas of the visual field, the measurement technique of multifocal evoked potentials (mfVEP) was invented, with which potentials can be assigned to certain retinal areas. In neurology, VEP are mostly used for testing for optic neuritis,mainly in the context of multiple sclerosis (MS) and neuro- myelitis optica spectrum disorders (NMOSD). In MS, latency delay and amplitude reduction are typical in the acute stage, after subsiding only latency delays are typical. In NMOSD, a very strong reduction of the amplitude is a typical sign. MfVEP confirm pathological changes of VEP, but also show a central amplitude reduction in MS, while in NMOSD the central potentials are almost extinguished. In other neurolog- ical diseases, changes in VEP may occur, but are not specific, therefore they do not bring any additional clinical benefit to the diagnosis. Conclusion. In neurological diseases, VEP can show specific changes, especially in optic neurites, and can therefore bring clinical added value in finding a diagnosis. Keywords VEP, Multiple Sclerosis, Parkinson’s, Alzheimer’s, Migraine

Clinical profile of ultrasonographic features and visual evoked potential changes in patients of ocular trauma with opaque media – A prospective study

To study the ultrasonographic features and VEP changes in eyes with ocular trauma having opaque media and the effect of such changes on the visual prognosis of these patients. A prospective study of total 80 patients with ocular trauma attending the eye outpatient department in a tertiary care hospital was conducted. Their USG B scan and VEP examination was done in the Radiology department and Neuromedicine department respectively.Blunt trauma was the cause of ocular injury in 60% of the patients, penetrating trauma in 25% and rest 15% had non-mechanical injury caused by acid burns, firecrackers.Complications of ocular trauma e.g. cataract, vitreous haemorrhage and retinal detachment etc. could be detected to the extent of 93.12% accuracy by ultrasonography alone as compared to only 70.22% by clinical examination when both clinical examination and ultrasonography were combined together, 100% accuracy in diagnosis was reached. 96.25% of control eyes had a visual evoked potential latency, ranging between 81-110 msec and 88.75% had a VEP amplitude ranging from 6-15 µv. 66.25% of injured eyes had delayed visual evoked potential latency with the mean latency at 123 msec and about 41.25% had reduced VEP amplitude with the mean amplitude at 6.125 µv. Thus both the latency and amplitude were decreased significantly in injured eyes as compared to control eyes. Good post-treatment visual acuity was achieved in only 27.5% of patients. : UBM is a very useful primary investigation to detect the posterior segment pathology in case of opaque media in traumatic eye. The VEP is affected in case of sight threatening findings. Thus VEP studies were more accurate than USG in predicting vision threatening ocular damage and the final visual outcome in this study.

Visual Evoked Potential and Voltage Changes Associated with Acute Concussion and Frequency Specific Photophobia

ObjectiveIn this paper we present a case series of concussion patients' VEP as well as a single concussion patient with a VEP baseline and post concussion VEP data.BackgroundVisual Evoked Potentials (VEP) are a means of measuring the electrical behavior of the brain following a visual stimuli. The use of VEP for diagnostics following traumatic brain injury (TBI) is emerging with additional data concerning sports related concussion coming.Design/MethodsDuring the 2016 spring football season there was 1 concussion of a subject who had a VEP baseline and a VEP performed during the acute phase of the concussion. Concurrently we have been using VEP for concussion patients who have not had a baseline. Fifteen subjects in the post acute phase; while symptomatic, had VEP performed using White, Red, Blue and Green for the evoked potentials.ResultsThe patient with a VEP baseline had increased voltages with subtle slowing of N75 and P100. N75 increased from 67.5 msec at baseline to 75.1 msec post concussion. Voltages went from 19.3 mVolts to 24.6 mVolts post concussion. Also, the colored flashes associated with the lowest voltages were consistent with mitigation of frequency specific photophobia; 20.9 mVolts for mitigation color compared (red) to 24.6 for white. In the concussion population studied (N = 15) the voltages where the color corresponded to symptom relief were: 10.9 ± 5.7 mVolts compared to symptom evoking voltages 12.7 ± 6.3 (p = 0.0031) mVolts.ConclusionsIn this paper we present evidence of VEP changes in one acute concussion patient as well as a population of concussion patients where voltages are increased post concussion. The increased voltages associated with color VEP may be a useful technique to assess frequency specific photophobia as well as helping manage post concussion photophobia. Futures studies to assess the utility of VEP as a concussion management tool are needed.

Visual Evoked Potential in Patients of Type 2 Diabetes Mellitus with and without Diabetic Retinopathy

Introduction
 Diabetes mellitus is a leading public health care problem, with increasing incidence and its long term complications. Diabetic retinopathy is a common complication of DM that affects retinal blood vessels. Unfortunately, in many cases the patient is asymptomatic until it is too late for effective treatment. VEPs are produced by electrical activity of the visual cortex in response to light or pattern stimulation of the eye. It can detect functional loss in the visual pathway from retina to the visual cortex.
 Aims and Objectives
 The aim of the study is to compare latencies and amplitudes of P100 waveform of VEP in diabetic and control subjects and to determine whether changes in VEP response occur before clinically evident diabetic retinopathy on fundus examination.
 Method
 PRVEP was recorded in 60 diabetic patients including 30 patients without any retinopathy and 30 others with non-proliferative diabetic retinopathy(NPDR), and compared to 60 age and sex matched normal non diabetic healthy controls. VEP was recorded using pattern reversal stimulation with RMS EMG MARK II machine. P100 wave latencies and amplitudes were obtained in all the subjects.
 Results
 Our results show significantly prolonged P100 latencies of VEP’ s in Type 2 DM patients and DR patients when compared to controls. The difference between diabetics with retinopathy and controls were significant in terms of P100 amplitude. However, there was no significant difference observed in the P100 amplitudes of VEP’ s in Type 2 DM patients without retinopathy when compared to controls.
 Conclusion
 The present study clearly shows that changes in VEP may be detected in diabetics before the onset of retinopathy. Thus, a routine VEP assessment should be recommended to all the diabetic patients, for the early identification of visual defects and for early and proper management of the disease.

VISUAL EVOKED CORTICAL POTENTIALS IN THE CHILDREN PRESENTING WITH CRANIOSYNOSTOSIS. THE DESCRIPTION OF THE CLINICAL CASES AND THE ANALYSES OF THE LITERATURE DATA

This article is devoted to the abnormalities of the visual function associated with the rare and severe congenital pathology - craniosynostosis in the hildren. We observed three clinical cases of partial craniosynostosis: scaphocephaly, plagiocephaly, and trigonocephaly. In addition to the standard ophthalmologic examination, we carried out the electrophysiological study to measure visual evoked potentials r (VEP). In the case of trigonocephaly, we documented significant changes in the amplitude-time characteristics of VEP and revealed partial atrophy of the optic nerves. Strabismus was detected in the cases of plagiocephaly and trigonocephaly. We obtained evidence of the association between different types of craniosynostosis and the anatomical features, such as location of the cranial sutures, and the manifestations of the pathological process underlying the changes in VEP especially its amplitude and temporal characteristics. They included the prolonged implicit time of the PI00 component most pronounced in the cells with the angulsar size of 8 minutes and the decrease of the PI00 peak amplitude. The damage to the optic nerves, especially the secondary one, due to the papilledema can be prevented by the early diagnostics of craniosynostosis. When craniosynostosis is suspected in the children, they need to undergo the ophthalmological examination. Early diagnostics with the use of not only the standard methods of ophthalmological studies but also of electrophysiological investigations allows to significantly improve the prognosis in different types of craniosynostosis in the children.

The changing shape of the ISCEV standard pattern onset VEP

PurposePattern onset VEPs do not always show distinct C1–C2–C3 peaks and troughs. Our purpose was to study changes in pattern onset VEP with age to determine when the illustrated ISCEV standard onset VEP waveform can be reliably recorded.MethodsWe recorded pattern onset VEPs from an Oz electrode referred to mid-frontal electrode according to ISCEV standards by presenting checks of 60′ and 15′ side length in a 15° field. Twenty-four adults aged 20–63 years participated. Amplitudes and latencies were collated. Pattern onset adult VEP shapes were compared to the waveform published in the ISCEV VEP standard and to paediatric pattern onset VEP waveforms recorded from 16 infants aged 7 months.ResultsThe shape of the pattern onset VEP changed gradually with age. The C1–C2–C3 morphology of the ISCEV standard pattern onset VEP becomes apparent consistently after 40 years to 60′ check stimulation. As age increases a negative trough, C2 is more frequently seen; however, the broad positive peak which characterises infant onset VEPs may still be recorded at 20 years. The group median measurements of onset VEPs to 60′ were C1 7 µV@ 88 ms (range 67–110 ms), C2 9 µV@109 ms (range 89–158 ms) and C3 13 µV@121–246 ms. To smaller 15′ checks, peak latencies were earlier and C2 became more obvious. The group median measures of onset VEPs to 15′ were C1 2 µV@69 ms (55–108 ms), C2 10 µV@90 ms (77–145 ms) and C3 14 µV@122 ms (99–200 ms).ConclusionThe ISCEV standard onset VEP best describes the waveform configuration and latency of the onset VEP produced by 60′ checks in adults of more than 40 years of age. The onset VEP waveform produced by 15′ checks is distinguished by more prominent negative C2 and earlier C1 and C2 latencies.

A study on early detection of changes in visual pathway due to diabetes mellitus by visual evoked potential

Electrical potentials have been recorded by surface Evoked Potentials namely the Somatosensory Evoked Potential, Auditory Brainstem Response and Visual Evoked Potential [VEP]. Visual conduction disturbance can be evaluated by these instruments. A mass response of cortical and possibly subcortical may be represented, visual areas to visual stimuli. Diabetic patients without a past history of cerebrovascular accidents diagnosed with Non- Proliferative Diabetic retinopathy[DR] with a best corrected visual acuity at least 6/9.This study was done to assess whether a delay in VEP latency observed in diagnosed type II DM patients could be ascribed to dysfunction of the retinal or post retinal structures or by both. It is to find out whether the VEP latencies are altered in diabetes or not, if altered and to correlate duration of the diabetes mellitus with visual evoked potential changes. Visual evoked potentials are useful as a non invasive investigatory method in establishing central nervous system neuropathy developing in diabetes. This study clearly shows that changes in VEP may be detected in diabetics before the onset of retinopathy. Future studies should be focused on evaluation of the time that elapses between the appearance of the first detectable pathologic electrophysiologic changes and the first ophthalmoscopically detectable retinal changes in patients with Diabetes Mellitus [DM].

Prediction of visual evoked potentials at any surface location from a set of three recording electrodes

Purpose of this study was to introduce a mathematical model which allows the calculation of a source dipole as the origin of the evoked activity based on the data of three simultaneously recorded VEPs from different locations at the scalp surface to predict field potentials at any neighboring location and to validate this model by comparison with actual recordings. In 10 healthy subjects (25-38, mean 29 years) continuous VEPs were recorded via 96 channels. On the base of the recordings at the positions POz', O1' and O2', a source dipole vector was calculated for each time point of the recordings and VEP responses were back projected for any of the 96 electrode positions. Differences between the calculated and the actually recorded responses were quantified by coefficients of variation (CV). The prediction precision and response size depended on the distance between the electrode of the predicted response and the recording electrodes. After compensating this relationship using a polynomial function, the CV of the mean difference between calculated and recorded responses of the 10 subjects was 2.8 +/- 1.2%. In conclusion, the "Mini-Brainmapping" model can provide precise topographical information with minimal additional recording efforts with good reliability. The implementation of this method in a routine diagnostic setting as an "easy-to-do" procedure would allow to examine a large number of patients and normal subjects in a short time, and thus, a solid data base could be created to correlate well defined pathologies with topographical VEP changes.

The use of VEP in the evaluation of optic nerve lesions

Abstract Purpose: To describe the use of VEP and other electrophysiological investigations in the assessment of optic nerve function. Methods: The techniques for recording ISCEV Standard VEP, ERG and PERG will be demonstrated. The clinical application of these techniques will be illustrated using selected cases. Results: The nature of the VEP changes in various disorders of optic nerve function will be described. Particular emphasis will be placed on the ability of electrophysiology directly to assess the function of the retinal ganglion cells, and to facilitate, in most cases, the distinction between optic nerve and macular dysfunction. Conclusions: The objective data provided by VEP and other electrophysiological investigations play an important role in the mangement of patients with suspected optic nerve disease.

Effects of single-pulse transcranial magnetic stimulation (TMS) on functional brain activity: a combined event-related TMS and evoked potential study.

To further evaluate the potential of slew-rate limiting amplifiers to record electrophysiological signals in spite of concurrent transcranial magnetic stimulation (TMS), and to explore the effects of single-pulse TMS on electroencephalographic (EEG) correlates of functional brain activity. Visual-evoked potentials (VEPs) to checkerboards were recorded in 7 right-handed subjects, while single-pulse TMS was applied to the occipital pole either at visual stimulus onset, during the build-up or at the expected peak of the early VEP component P1 (VIS&TMS). Timing of TMS was individually adjusted based on each subject's VEP-latency. A condition of TMS without concurrent visual stimulation (TMS(alone)) served for subtraction purposes (VIS&TMS minus TMS(alone)) to partial out TMS-related contaminations of the EEG signal. When TMS was applied at visual stimulus onset, VEPs (as calculated by subtraction) perfectly matched control VEPs to visual stimulation alone. TMS at around P1, in contrast, modified the targeted (P1) and the subsequent VEP component (N1), independently of whether TMS was given at build-up or peak. The retrieval of regular VEPs with concomitant TMS at visual stimulus onset suggests that the employed EEG system and subtraction procedure are suited for combined EEG-TMS studies. The VEP changes following TMS at around P1 provide direct clues on the temporal dynamics of TMS pulse effects on functional activity in the human brain. Our data suggest effects of relatively long duration (approximately 100 ms) when TMS is applied while functional neuronal activity evolves.

This Issue of Acta

Several contributions in this issue deal with treatment of age-related macular degeneration with transpupillary thermotherapy (TTT). Macular degeneration has defied intensive therapeutic efforts for a long time, and it may be motivated to consider TTT as great a promise for patients with macular degeneration as photodynamic therapy (PDT). TTT can also be administered at a fraction of the cost as compared to PDT. The results reported by Algvere and coworkers in a safety and efficacy study are commented on in the Guest Editorial by Ciulla, who concludes that the results of the large prospective material in Algvere's paper ‘corroborate and amplifies the previous studies that suggest a role for TTT in the treatment of occult CNVM, lesions with minimal or no benefit from PDT’. These results are very important, and we must agree with Ciulla that we are now at the stage when we must look forward to the results of a randomised, prospective TTT trial. Everything has a downside, however. Salinas-Alamán and coworkers describe a case of over-treatment with TTT in a letter to the editor. The review article in the current issue is on a highly modern subject: telemedicine in ophthalmology, authored by Lamminen and coworkers. Telemedicine holds great promise making specialty care available everywhere. Studies have shown that the concept works, but cost efficiency has not been conclusively proven. The potential value of telemedicine is particularly large in the Nordic countries, where distances are often great. The technological solutions are available, and we are waiting for a situation when also the organisational aspects have been addressed and solved. The Clinical Questions and Answers section discusses the management of a patient with an inadvertent filtration bleb after phacoemulsification with suture-less wound closure. The patients had disturbing symptoms, and treatment was not without problems. Primary papillary pigment epithelial iris cysts are rare. In the Diagnosis and Therapy in Ophthalmology section Sallo and coworkers show beautiful pictures pre and post surgery in two patients with this condition. Original articles in this issue cover a broad spectrum of ophthalmology. In an unusual, prospective study Tranos and coworkers have compared the subjective visual experience of patients during phacoemulsification and IOL implanation with regional versus topical anesthesia. A study by Splunder and coworkers involving 900 Dutch adults with profound intellectual disabilities found that many had nonoptimal spectacle correction and that more than half of those needing reading glasses did not have them. The results are similar to those reported by Warburg in this journal (Warburg 2001), and suggest that visual function screening is motivated in persons with intellectual disabilities. Fahnehjelm and colleagues describe four cholestatic infants with optic nerve hypoplasia; three of them were blind or had low vision. Early assessment by paediatric ophthalmologists is important in children with neonatal cholestasis. Uretmen and coworkers have studied psychosocial implications of strabismus– reactions of school teachers to digitally altered photographs of children with and without strabismus, and showed that the children were rated more negatively when strabismic. Fledelius and coworkers report findings of orbital ultrasound sonography in a large series of patients with thyroid-associated orbitopathy. Most patients had increased muscle thickness, and the examination techniques could not discern between inflammatory and fibrotic changes. Two studies deal with glaucoma. Naruse et al. describes a new technique to remove the inner wall of Schlemm's canal during nonpenetrating surgery using cyanoacrylate. Inan and coworkers found increased blood flow velocities in retro-bulbar vessels both in eyes treated with latanoprost and with brimonidine. Akyol et al. found that levels of serum trace elements were considerably lower in chronic heavy smokers than in controls, and were associated with reductions in contrast sensitivity functions. Trace element alterations may play a causative role in the smoking induced retinal toxicity. Conjunctival papillomas may be very difficult to treat. Keizer and de Wolff-Rouendaal describe two cases with conjunctival papillomas that were successfully treated with alpha-2-interferon eye drops, after previous unsuccessful management with a variety of treatment modalities. There are many basic science papers in this issue. Söderberg et al. have developed a new method to estimate a threshold UV radiation dose for cataract. Wiencke and coworkers found that not only ‘good looks’ (histologically!), but also DNA profiles should be taken into account when retinal pigment epithelium is cultured for transplantation purposes. Two articles have studied Vitamin E. Bilgihan et al. investigated the effects of this vitamin administered topically in conjunction with photorefractive keratectomy. Yargicoglu found that vitamin E had a protective effect against stress-induced VEP changes in a rat model. And do not forget to read some interesting letters in this issue!

Visual electrophysiology in Parkinson's disease: PERG, VEP and visual P300.

A retinal dopaminergic deficiency underlies some visual changes in Parkinson's disease (PD), in particular those elicited by stimuli near the peak of the human and monkey spatial contrast sensitivity. The correspondence of retinal changes and VEP alterations is not perfect: they do not seem to rely on identical mechanisms. It seems that additional pathology beyond the retina affects visual responses, including VEPs. The relevance of "distal" primary VEP changes to higher cognitive visual abnormalities in PD is not established at present.

Visual evoked potentials in rubber factory workers.

Pattern reversal visual evoked potentials (pVEP) were studied in 39 male rubber factory workers in the age range of 18-55 years and 20 control subjects (aged 18-46 years) not exposed to the rubber factory environment. Results revealed that 20 (51%) rubber factory workers had abnormal latencies of wave P1 (dominant component of pVEP) as per accepted criteria of 99% tolerance limit set for the control group (i.e. any value above mean +3 SD of control was considered abnormal). The section-wise per cent distribution of abnormalities was vulcanization (83%), tubing (75%), calendering (60%), loading (38%) and mixing (14%). This study provides electrophysiological evidence that rubber factory environments affect the conduction processes in optical pathways from their origin in the retina to striate cortex. However, this study has its limitations in not identifying the specific chemical(s) causing these changes in VEP.

Dysfunction of visual pathways in HIV-1 infection

Foveal and conventional full field pattern-shift visual evoked potentials (f-VEPs and c-VEPs) were recorded bilaterally in 100 HIV seropositive homosexual men (HIVs) and in 40 age-matched healthy controls. In HIVs, both f-VEPs and c-VEPs revealed a significant mean increase in P100 latency ( p < 0.001). In stage WR2 early conduction changes were detected in 17% of the stimulated eyes by f-VEPs and in 3% by c-VEPs. In patients with CD4 cell counts below 100/μl a 33% reduction in the mean c-VEP amplitude was found (ANOVA p < 0.01). Multivariate analyses (MANCOVA) revealed that CD4 cell depletion was independently associated with lower ( p < 0.01) and zidovudine treatment with higher c-VEP amplitudes ( p < 0.05). Also patients with severe CD4 cell depletion showed a trend towards higher c-VEP amplitudes ( p = 0.09) and lower f-VEP latencies ( p = 0.08) after long lasting zidovudine treatment (Kruskal-Wallis test). Our data suggest that f-VEPs are a sensitive measure of subclinical optic fiber dysfunction in early HIV-1 infection and that axonal loss of optic fibers emerges with manifest immune deficiency. The inverse correlation of VEP changes and zidovudine treatment merits further studies on the question, whether inhibition of HIV replication may preserve visual pathway function.

Visual evoked potentials and optic nerve histopathology in normal and diabetic rats and effect of ginkgo biloba extract

The purpose of this study was to test the possible therapeutic role of ginkgo biloba extract on the impairment of visual function and pathological histology of the optic nerve caused by early diabetes. Ginkgo biloba extract entraps oxygenated free radicals and is also a strong inhibitor of the platelet activation factor (PAF). For this purpose, VEP recordings and optic nerve histopathology were studied on alloxan diabetic and normal Swiss albino rats in four experimental groups. The VEP recordings showed no statistical significance between diabetic and normal rats. However, the amplitudes were significantly increased in diabetic animals with ginkgo biloba extract compared with the diabetics, supposing an impression of axonal protection. But the amplitude values were decreased in normal rats treated with the same extract compared with normal animals, assuming a toxic activity. Optic nerve ultrastructural findings also confirmed these VEP changes. It was concluded that this extract could be encouraging for human clinical trials of diabetes.

Neonatal cataract: aetiology, pathogenesis and management.

We review the epidemiology, aetiology, pathogenetic mechanisms and clinical management of neonatal cataract. Visual development and the effects of visual deprivation in the infant with congenital cataract are discussed and related to the timing of surgery. Surgical techniques and the important operative and post-operative complications are discussed. We review post-operative management and compare the different techniques available for aphakic correction, and describe the VEP changes found in patients with monocular cataract.

Formveränderungen des Kontrast-VEP bei multipler Sklerose: Beziehung zum Läsionstyp

VEP changes in MS patients are due to the demyelinating process which causes conduction alterations as well as inhibitory mechanisms. The pattern-shift VEP can show a delay of the main positivity, a diminished amplitude or/and an altered shape and duration. Concerning to series from the literature and own observations on more than 500 MS patients 4 different types of VEP alterations can be observed: 1. NPN complex with P2 delay; 2. broadening with loss of N2 and P2 delay; 3. bifid P2, P100-P135 complex; 4. deformation and dissociation with loss of P2, N105 dominance and amplitude reduction.

Leber's optic atrophy: VEP and BAEP changes in 16 asymptomatic subjects

Leber's optic atrophy: VEP and BAEP changes in 16 asymptomatic subjects

Visual-evoked potentials and electroretinograms in ruminants with thiamine-responsive polioencephalomalacia or suspected listeriosis

SUMMARY Electrodiagnostic visual testing (electroretinogram [erg] and visual-evoked potential [vep]) was performed on 5 ruminants (3 lambs, 1 kid, and 1 steer) with thiamine-responsive polioencephalomalacia (pem) and on 2 sheep with listeriosis. The lambs and kid had typical clinical signs of pem, especially blindness. In these animals, the erg was normal but the vep was abnormal. Follow-up recordings in the kid and 1 lamb indicated an improvement in vep recordings accompanying a gradual return of vision after thiamine treatment. Possible subtle changes in vep peak latencies could not be assessed because of lack of normative vep data for sheep and goats. All animals had complete return of vision (owner-assessed). The steer did not have signs of blindness, and the erg and vep were normal. Changes in vep accompanying permanent pem blindness are not known. One sheep with suspected listeriosis had lack of menace response and palpebral and corneal reflexes, but had intact vision. The erg and vep were normal. The second sheep with suspected listeriosis had intact menace response and vision, but became acutely blind and died; the ERG was normal, but vep amplitudes were depressed.

VEP changes related to the motor self-stimulation

VEP changes related to the motor self-stimulation