Flash Visual Evoked Potentials Research Articles

The Value of Visual Evoked Potentials in the Evaluation of Periorbital Hemangiomas

To present a case of a child with an extensive facial hemangioma in whom the suspicion of intracranial involvement was raised by visual evoked potential (VEP) evaluation. Observational case report. VEP analysis was performed using flash and pattern stimuli to determine whether treatment intervention other than occlusion therapy was needed. VEP analysis indicated a marked transoccipital asymmetry in the flash and pattern VEP suggestive of right hemispheric dysfunction. Neuroimaging showed intracranial extension of the hemangioma. The VEP evaluation is a noninvasive technique performed in the awake child. This case highlights the usefulness of VEP analysis in the management of extensive periocular capillary hemangiomas and its use as a modality to identify potential intracranial involvement. Large plaquelike facial capillary hemangiomas may have possible underlying dural involvement suggestive of PHACES syndrome.

FVEPs in Creutzfeldt–Jacob disease: waveforms and interaction with the periodic EEG pattern assessed by single sweep analysis

Objective To characterise flash visual evoked potentials (FVEPs) in 20 patients with Creutzfeldt–Jacob disease (CJD), and assess the relationships between spontaneous EEG patterns and the responses to individual stimuli. Methods We analysed the shape and time course of periodic sharp wave complexes (PSWCs) and responses to 1 Hz flashes. In nine patients, we applied an algorithm based on an autoregressive model with exogenous input (ARX) to estimate responses to individual random flashes and their interaction with PSWCs. Results The FVEPs included P1 and N1 components in all patients, and the P2 peak in 18. Eight patients showed giant FVEPs (N1-P2>60 V), all of whom had an MM polymorphism in codon 129 of the prion protein gene; in seven cases, the presence of giant FVEPs correlated with a prominent and almost continuous periodic EEG pattern. Giant N1-P2 abnormally spread on the anterior scalp regions, and had a different waveform distribution from that of the PSWCs. In five patients with a normal or slightly enlarged average N1-P2 amplitude, single sweep (ARX) analysis revealed a period of relative refractoriness following individual PSWCs. In four patients with ‘giant’ FVEPs, the individual responses occurred regardless of the interval between the stimulus and previous PSWC, but their amplitude had an inverse relationship with the interval length. Conclusions Giant responses to flash stimuli are a common finding in CJD patients (40% of our cases). Single sweep ARX analysis showed that PSWCs were followed by a period of partial refractoriness, which prevented most of the individual responses to flashes, but not giant FVEPs. The association between prominent spontaneous paroxysms and giant FVEPs suggests that both are due to a common hyperexcitable change favouring neuronal synchronisation. Significance Our data contribute to clarifying the debated problem of the occurrence of giant FVEPs in CJD and their relationships with the spontaneous periodic EEG pattern.

Visual evoked potential actuated brain computer interface: a brain-actuated cursor system

Flash visual evoked potential (FVEP), induced by OFF-to-ON flash, i.e. flash onset, in a light emitting diode (LED) was used to control four cursor movements (left, right, up, down), and left- and right-button clicks on a screen menu. ON or OFF duration in each flashing sequence was designed to be random so that all flashing sequences were mutually independent. Since FVEPs are time-locked and phase-locked to flash onsets of gazed LEDs, segmenting EEG signals based on the flash onsets of each flashing sequence followed by averaging will sharpen epochs evoked by gazed LEDs. Four inexperienced subjects were asked to generate a sequence of cursor commands. Mean recognition and transfer rates were 88% and 3.74 s/command, respectively.

Topographic Analysis of Flash Visual Evoked Potentials in Dogs

Visual evoked potentials by flash stimulation (flash VEP) were analyzed in dogs using a topographic method. The flash VEP consisted of 3 positive (P1, P2 and P3) and 2 negative (N1 and N2) components by 150 msec after the flash stimuli. On the topographic mappings, a negative response area was observed in the frontal region of the scalp in the stimulated site followed by the shifting of the area to the contralateral frontal region and occipital region, during the first 100 msec. The negative response area in the frontal region in the stimulated site, contralateral frontal and temporal region, and occipital region were corresponded to N1, P2, and N2 on the flash VEP, respectively, according to their latencies. In the dogs with experimentally impaired the right lateral geniculate body, the latency of P2 was prolonged, and N2 and P3 were disappeared after the left eye stimulation. On the topographic mapping, only the early negative response area was detected on the stimulated site of the frontal region of the brain. Therefore, it is concluded that P1 and N1, P2, and N2 are referred to the retinal potentials, the potentials from the retina to the brainstem included the lateral geniculate body, and those from the brainstem to the visual cortex, respectively.

Disturbed visual system function in methionine synthase deficiency

Isolated functional methionine synthase deficiency occurs in the cblE and cblG defects of methylcobalamin metabolism and is one of a number of causes of severely elevated plasma homocysteine. Clinical features are predominantly of a neurological nature but also include functional restriction of the visual system manifesting as loss of visual acuity and nystagmus. As yet, the origin and pathogenesis of impaired vision have not been explained. We investigated a patient who was proven by complementation analysis in cultured fibroblasts to belong to the cblG complementation group. Ganzfeld electroretinograms (ERG) and flash visual evoked potentials (VEP) were recorded over a period of 4 years. Amplitudes of all International Society for Clinical Electrophysiology of Vision (ISCEV) standard responses were below normal. The greatest reductions were of rod response to 24 microV, of standard combined response (SC) b-wave to 120 microV, of oscillatory potentials (OP) to 5 microV, of cone response b-wave to 35 microV, and of 30 Hz flicker response to 8 microV. Except for SC and cone a-waves at age 2.5 and 3.5 years, as well as cone b-wave at 3.5 years, amplitudes remained at a subnormal level at follow-up examinations. Implicit times were slightly prolonged (SC b-wave 6 ms, OPs 2 ms, cone b-wave 2 ms, 30 Hz flicker 4 ms) or fell within the normal range. Responses of the flash VEP were severely deformed but reproducible. This is the first report of detailed investigations of the visual system in a patient with isolated methionine synthase deficiency. Reduced oscillatory potentials suggest microvascular damage to the retina through homocysteine. Decreased photoreceptor function as well as ganglion cell loss as indicated by pathological flash VEPs may reflect a cytotoxic impact of homocysteine on neurons of the visual pathway.

Effects of flash mode and intensity on P2 component latency and amplitude

Alzheimer's disease (AD) groups manifest flash visual-evoked potential (VEP) P2 component delays compared to healthy control groups. However, using P2 latency to categorize individual patients and controls yields low accuracy. Additionally, several laboratories have failed to replicate the basic between group P2 latency findings. The sporadic failure to find the P2 delay and, when found, its failure to classify patients and controls accurately may reflect the use of non-optimal stimuli or recording sites. Objective This was a parametric investigation of stimulation and recording methods in healthy college students. Method Using an extended recording montage of 64 electrodes, 10 stimulus conditions (5 flash intensities through open and closed eyes) were evaluated for their P2 effects. Result The optimal recording site (O2) yielded the most reliable latencies and amplitudes across a range of stimulus intensities. Flash intensity did not affect P2 latency or amplitude. Flashes delivered through closed eyelids produced a flash VEP but delivery through open eyes produced a pattern VEP lacking a flash P2 component. Conclusion This accounts for the failure of some laboratories using open eyes to replicate the P2 delay in AD groups. Significance Optimal flash VEP conditions include closed eyes and recording from O2. Flash intensity is unimportant.

The evolutionary change of flash visual evoked potentials in preterm infants with periventricular leukomalacia

Objective The aim of this study was to prospectively investigate flash visual evoked potential (VEP) findings and their chronological changes in preterm infants with cystic periventricular leukomalacia (PVL) during the early neonatal period. Methods The subjects of this study were 14 preterm infants with cystic PVL. The patients underwent serial cranial ultrasonography and diagnosed as having cystic PVL. Flash VEPs were diagnosed at least twice within the first 3 weeks of life. Results All infants had at least one or more flash VEP abnormalities. The most common finding was ‘absent VEP’, which was seen in 13 infants (93%). ‘Delayed latency’ was seen in two infants and ‘abnormal waveform’ was seen in one infant. Concerning the chronological changes, all records were abnormal in 4 infants, and the other 10 had transient normal VEP findings. Among them, flash VEPs changed from normal to abnormal within 10 days after birth in most cases. Conclusions Almost all infants with cystic PVL had abnormal flash VEPs within the first 3 weeks of life, but chronological changes of flash VEP findings were seen during the period. Significance This manuscript may be useful as a reference to the flash VEPs in preterm infants with cystic PVL.

Flash visual evoked potentials predict visual outcome in traumatic optic neuropathy.

To determine the significance of flash visual evoked potentials (FVEP) in the evaluation of patients with traumatic optic neuropathy (TON). Eleven head-injured patients admitted to our center were diagnosed with unilateral TON. For every patient, FVEPs were obtained in both the affected eye and the unaffected eye. The normal eye thus functioned as each subject's internal control. We determined the amplitudes of FVEP waveforms for each eye and calculated an amplitude ratio of the affected/normal side for all individuals. The best-corrected visual acuity was obtained for each eye 2 weeks after acute hospitalization. We then determined the relation between best-corrected visual acuity in TON and the FVEP amplitude ratio. In 4 patients in whom the amplitude ratio was at least 0.5, visual acuity in the affected eye was 20/30 or better. In 7 patients, the amplitude ratio was less than 0.5, and visual acuity in the eye with TON did not exceed 20/300 (Pearson r = -0.93, p = 0.0001). Flash visual evoked potentials are highly predictive of the degree of visual function in unilateral TON. Finding FVEP amplitudes that are at least 50% of the normal eye appears to be critical in anticipating good, long-term visual outcome.

Flash visual evoked potentials on newborns and infants

To explore the feasibility of applying flash visual evoked potentials (FVEPs) for visual function test newborns and infants and bring out the consultable laboratory values of FVEPs. The technology of FVEP could be used as diagnostic tests for those who failed the screening and the infants who were cared for in the NICU. 41 normal neonates (<or= 4 days) and 18 normal infants (<or= 5 months) were tested with FVEP by Nicolet Viking-IV model evoked potentials apparatus. Get the normal reference range of FVEPs latency in both groups and the consulting value of the difference between the left and right eyes. It has been observed from the paper that the latency of FVEPs has the tendency to shorten with the age increasing. It also shows that there are extreme significant changes of FVEPs (P < 0.05) by different frequency of stimulating light. The latency of FVEPs P1 is steady and could be applied to newborns-infants visual function test. While, the references of FVEPs according to different age group should be taken into account when we using this measure in clinic.

Large-scale screening of disease model through ENU mutagenesis in mice

Manipulation of mouse genome has merged as one of the most important approaches for studying gene function and establishing the disease model because of the high homology between human genome and mouse genome. In this study, the chemical mutagen ethylnitrosourea (ENU) was employed for inducing germ cell mutations in male C57BL/6J mice. The first generation (Gl) of the backcross of these mutated mice, totally 3172, was screened for abnormal phenotypes on gross morphology, behavior, learning and memory, auditory brainstem response (ABR), electrocardiogram (ECG), electroretinogram (ERG), flash-visual evoked potential (F-VEP), bone mineral density, and blood sugar level. 595 mice have been identified with specific dominant abnormalities. Fur color changes, eye defects and hearing loss occurred at the highest frequency. Abnormalities related to metabolism alteration are least frequent. Interestingly, eye defects displayed significant left-right asymmetry and sex preference. Sex preference is also observed in mice with abnormal bone mineral density. Among 104 Gl generation mutant mice examined for inheritability, 14 of them have been confirmed for passing abnormal phenotypes to their progenies. However, we did not observe behavior abnormalities of Gl mice to be inheritable, suggesting multi-gene control for these complicated functions in mice. In conclusion, the generation of these mutants paves the way for understanding molecular and cellular mechanisms of these abnormal phenotypes, and accelerates the cloning of diseaserelated genes.

Unusual neurophysiological features in Cockayne's syndrome: a report of two cases as a contribution to diagnosis and classification

To clarify the diagnostic value of neurophysiological investigations in patients with Cockayne's syndrome (CS). The study involved two patients with clinical diagnoses of classical and severe CS, who were neurophysiologically evaluated by means of: (1) multimodal visual (VEPs), brainstem auditory (BAEPs) and upper limb somatosensory (SEPs) evoked potentials; (2) electroretinography; and (3) nerve conduction and needle electromyography studies. Both patients showed multimodal evoked potential (EP) signs of central nervous system involvement that overlapped in severity and extent, and were consistent with demyelination along the central sensory pathways. Flash VEPs and SEPs were more altered than pattern VEPs and BAEPs. No signs of retinopathy or hearing loss of cochlear origin were detected. The nerve conduction and needle electromyography studies showed severe signs of sensory and motor demyelinating and axonal peripheral neuropathy. Peripheral neuropathy was clinically uncertain. There were no significant differences between the two patients. Our results show that combined multimodal EP and nerve conduction studies are diagnostically highly sensitive even in the early stage of CS, but their ability to distinguish classical and severe CS is limited. The unusual features were characterised by the absence of clinical and electrophysiological signs of otherwise common retinopathy and neurosensory hearing loss. BAEPs seem to be more useful than VEPs or SEPs in the diagnostic work-up of patients with suspected CS.

Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO), Fort Lauderdale, Florida, May 5-10, 2002.

Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO), Fort Lauderdale, Florida, May 5-10, 2002.

Chiasmal coefficient of flash and pattern visual evoked potentials for detection of chiasmal misrouting in albinism.

The diagnosis of albinism can be confirmed by electrophysiological examination, when chiasmal misrouting can be demonstrated. The present study describes a quantitative analysis method for this purpose. A chiasmal coefficient (CC) was calculated by correlating the differential potential over left and right hemisphere, when stimulating left versus right eye. This CC will be negative in albinism and positive in normal individuals. VEPs were recorded in 20 control subjects, four children with congenital motor nystagmus and six children with albinism. In up to 25% of the controls the CC was negative, when using flash VEP. However, with pattern VEP all had a positive CC. All children with albinism had a negative CC. Three of the four patients with congenital motor nystagmus had a positive CC, and one child had a small negative value with flash stimulation. In conclusion, determination of CC is a valuable and objective analysis method for electrophysiological determination of chiasmal misrouting. The method is relatively simple and only needs two electrode tracings. One should be aware of false-positive results when using flash stimulation. Whenever possible pattern stimulation should be used.

Taller de electrorretinografía y potenciales evocados visuales

Studies of vision using electrophysiological techniques are tests which record functional alterations in very early phases of a disease. Full field flash ERG evaluates the integrity of the cones, rods and bipolar cells. It is obtained by photopsic stimulation with Ganzfeld and contact lens corneal electrodes or, alternatively, gold leaf or anchor electrodes. Five responses must be obtained: that of the rods, a maximum, oscillatory potentials, that of the cones and a flicker response. Pattern ERG is a response of the ganglionic cells, which is obtained by pattern reversal morphoscopic stimulation, with a bandwidth between 1 and 60 Hz. The fundamental waves (0.5 5 mV) are P50 (luminance) and N95 (pattern specific). This is of great value in the early diagnosis of glaucoma. VEP are electrical fields that are recorded in the calcarine cortex. They give information about alterations in the optic nerve, chiasm, radiations and cortex. Pattern VEP is obtained with a visual angle of between 13 and 14 . The fundamental wave P100 is evaluated according to its latency and amplitude, and by comparing it with a healthy eye. Flash VEP is only used on patients who do not collaborate or who present an opacity of media.

Color Responses of Flash Visual Evoked Potentials in Normal Adults, Normal Elderly Subjects and Dementia of the Alzheimer Type Using Light Emitting Diodes

Background: Since initially we could only employ the red light goggle‐shaped stimuli equipment with flash light emitting diodes (LEDs), we had little information concerning different color responses of visual evoked potentials (VEPs). On our request, Nihon Kohden (Tokyo, Japan) developed green light goggle‐shaped stimuli equipment with LEDs in 1999.The purpose of this study was to determine the effects of green and red flash VEPs in normal adults, normal elderly subjects and patients with dementia of the Alzheimer type (DAT). Methods: Subjects consisted of a normal adult group (n=30), normal elderly group (n=10), and DAT patients (n=7). Transient VEPs of 1 Hz were measured. The recording electrodes were placed at midline‐occipital, left‐occipital and right‐occipital sites in accordance with the ten‐twenty electrode system. Results: In the normal adult group, peak latencies of green flash VEPs increased significantly compared to those of red flash VEPs (N2, P3: p&lt;0.01, N3: p&lt;0.05). The N2 and P3 latencies of both red and green flash VEPs were delayed in the normal elderly and DAT groups compared with those in the normal adult group. The delayed latencies of red flash VEPs were greater than those of green flash VEPs. Conclusion: The difference in latency between green and red flash VEPs corresponds to the difference in the conducting time from three rods (each spectrum peak is 419–420 nm, 530–534 nm, and 558–564 nm) to the visual central system. Each channel from the three rods to the visual central system may have an individual speed reaction, individual ageing and pathological changes. The results indicate that the peak latency of red light reveal elderly and pathological change more easily than that of green light.

Flash Visual Evoked Potentials of Various Derivations in Dementia of the Alzheimer Type and Vascular Dementia

Background: Recently, evoked potentials have been used for objective monitoring of the cortical function in dementia. The aim of this study was to distinguish dementia of the Alzheimer type (DAT) from vascular dementia (VaD) using flash visual evoked potentials of various derivations. Methods: A total of 70 patients consulting Tachikawa Medical Center Kashiwazaki Kosei Hospital were divided into four groups, normal adult (29.5 ± 8.5 years, n=16), normal elderly (77.2 ± 4.7 years, n=17), VaD (81.1 ± 8.1 years, n=17) and DAT (77.4 ± 5.6 years, n=20). Red flash stimulation was provided by a pair of goggles. Visual evoked potentials (VEPs) to flash were recorded in accordance with the International 10–20 Electrode System. Results: The latencies of N130 and P190 of frontal and central derivations were significantly reduced in DAT compared with all other groups (p&lt;0.05). The N130 and P190 latencies were markedly delayed in the normal elderly group compared with the normal adult group (p&lt;0.05). The P3 (P100) latency of occipital derivation was significantly delayed in normal elderly, VaD and DAT groups compared with the normal adult group (p&lt;0.05). In the DAT group, the P190 latency was shortened at central and frontal derivations compared with that at occipital derivation (p&lt;0.05). Conclusions: The N130 and P190 latencies decreased at frontal and central derivations in DAT. While the reason is still unclear, dysfunction in the central visual system induced by the degeneration of neuronal populations in DAT may cause the apparently reduced latency. Flash VEPs of frontal and central derivations may be useful for the differential diagnosis of DAT from VaD.

Evidence for functional regeneration of the visual pathway in adult rats

Mature nerve cell axons do not spontaneously regrow within their natural environment unless they are stimulated by external application of growth-promoting measures. In the present study, axonal regrowth and restoration of visual function was studied in adult rats. The optic nerve was completely cut, and its proximal and distal stumps were realigned and sutured back together. During the same surgical procedure, the lens was lesioned in order to induce secondary intraocular inflammation, which is known to strongly support the survival of retinal ganglion cells (RGCs) and to promote axonal regeneration within the distal segment of the optic nerve.The neuroanatomical data showed that cut axons can regenerate over long distances within the white matter of a central nerve like the adult optic nerve, spanning over 11mm to the chiasm and between 12 and 15mm to the thalamus and midbrain. Responsiveness of the pupil to light was restored five weeks after injury, thus indicating reinnervation of the pretectal nuclei. Restoration of the ascending pathway between the retina and visual cortex was assured by recording flash visual evoked potentials (FVEPs). As expected, no FVEPs could be recorded during the postsurgical period of axonal growth throughout the optic nerve and tract. FVEPs could be recorded after two months, indicating that synaptic transmission in higher visual areas was established.The recording findings and the restoration of pupillary responses suggest, for the first time, that lentogenic stimulation of RGCs is sufficient to induce the formation of growth cones that can override putative inhibitors at the site of injury.

Flash visual evoked potentials in the hypomyelinated mutant mouse shiverer.

Myelin basic protein (MBP) is an essential component of central nervous system (CNS) myelin, as demonstrated by shiverer mutant mice that have deletions of most of the Mbp structural gene. These mutants do not produce detectable MBP protein, and their CNS is hypomyelinated. Although the function of the visual pathway is presumed to be adversely affected by hypomyelination of the optic nerve, it has never been studied. We compared flash visual evoked potentials (FVEPs) of shiverer homozygotes with those of their wild-type littermates in order to characterize any dysfunction. There was a statistically significant delay in the implicit times of a negative component peaking at 85 ms and a large positive component peaking at 170 ms in the FVEPs of the shiverer mice. The amplitudes of the two components did not differ significantly in the shiverers and wild-type controls. Barring a retinal pathology, which cannot be excluded by these data, the delayed FVEP of the shiverer can likely be attributed to effects of hypomyelination of the optic nerve, optic tract and visual radiations on conduction time in the visual pathway and subsequent further post-synaptic delays.

Visual evoked potentials in children with neurofibromatosis type 1.

The purposes of this investigation were to determine: (a) if visual evoked potential (VEP) abnormalities could be identified in children with neurofibromatosis type 1 (NF1) with no evidence of optic pathway or brain neoplasias on MRI; and (b) if VEP abnormalities could be explained by the presence of hyperintense T2-weighted foci on MRI testing, known as unidentified bright objects (UBOs). To answer these questions, VEPs were recorded from 16 children with NF1 and compared to 13 normal subjects in the same age range tested with the same protocol. Pattern-reversal VEPs were recorded at four stimulus sizes both monocularly and binocularly, the latter to hemi-field stimuli. Flash VEPs were recorded in dark- and light-adapted conditions. VEP measurements and MRI readings for UBOs were conducted in a masked fashion. Ten of the 16 children with NF1 had abnormal VEPs to at least one of the four types of stimuli. Abnormalities included delayed responses (n=6), absent flash VEP P2 component (n=3), or both (n= 1). Abnormalities of the P2 component of the dark-adapted flash VEP were the most common finding (n=7), although no single testing strategy was able to identify all children with abnormal VEPs. UBOs were present in all children, demonstrating that their presence does not fully account for VEP abnormalities in children with NF1. This study also demonstrates that VEP abnormalities are present also in the absence of neoplasias of the optic pathways or of the brain. Our results are suggestive of a primary abnormality of visual processing in children with NF1.

Deletion in the OA1 gene in a family with congenital X linked nystagmus

AIMSTo elucidate the molecular genetic defect of X linked congenital nystagmus associated with macular hypoplasia in three white males of a three generation family with clear features of ocular albinism...