Optic nerve involvement in patients with Lyme neuroborreliosis: an electrophysiological study.

PURPOSE: The aim of this neurophysiological study was to retrospectively analyze visual evoked potentials (VEPs) acquired during an examination for diagnosing optic nerve involvement in patients with Lyme neuroborreliosis (LNB). Attention was focused on LNB patients with peripheral facial palsy (PFP) and optic nerve involvement. METHODS: A total of 241 Czech patients were classified as having probable/definite LNB (193/48); of these, 57 were younger than 40 years, with a median age of 26.3 years, and 184 were older than 40 years, with a median age of 58.8 years. All patients underwent pattern-reversal (PVEP) and motion-onset (MVEP) VEP examinations. RESULTS: Abnormal VEP results were observed in 150/241 patients and were noted more often in patients over 40 years (p = 0.008). Muscle/joint problems and paresthesia were observed to be significantly more common in patients older than 40 years (p = 0.002, p = 0.030), in contrast to headache and decreased visual acuity, which were seen more often in patients younger than 40 years (p = 0.001, p = 0.033). Peripheral facial palsy was diagnosed in 26/241 LNB patients. Among patients with PFP, VEP peak times above the laboratory limit was observed in 22 (84.6%) individuals. Monitoring of patients with PFP and pathological VEP showed that the adjustment of visual system function occurred in half of the patients in one to more years, in contrast to faster recovery from peripheral facial palsy within months in most patients. CONCLUSION: In LNB patients, VEP helps to increase sensitivity of an early diagnostic process.

New portable device for an examination of visual cognitive evoked potentials might extend their diagnostic applications in psychiatry.

Despite positive prior results obtained by using event-related potentials (ERPs) in psychiatric patients, they are not routinely used in the clinical setting. This may in part be due to problems regarding a lack of transportable equipment availability. It can be difficult for these patients to repeatedly visit electrophysiological laboratories. To address this issue, we propose using a new, fully portable device for visually evoked potentials (VEP) and cognitive function assessment, that can be used for quick examinations (https://www.veppeak.com). Our device, called "VEPpeak", is built into a headset with a color LED visual stimulator. It weighs 390 g and is connected to a notebook (PC) with evaluation software via USB. In this pilot study, we verified the device's usability in 31 patients with schizophrenia. We used the oddball paradigm with the recognition of colors for the P300 wave and choice reaction time evaluation. The examination lasted only about ten minutes. The results indicated good reproducibility of large cognitive potentials (P300) with prolonged P300 latencies and reduced amplitudes in patients compared to 15 control subjects. The P300 latency and reaction time prolongation in patients correlated with their age and the sedative effect of the pharmacotherapy.

VEP examination with new portable device.

INTRODUCTION: We developed a new portable device called "VEPpeak" for the examination of visual evoked potentials (VEPs) to extend VEP examination beyond specialized electrophysiological laboratories and to simplify the use of this objective, noninvasive, and low-cost method for diagnostics of visual and central nervous system dysfunctions. METHODS: VEPpeak consists of a plastic headset with a total weight of 390 g containing four EEG amplifiers, an A/D converter, a control unit, and a visual LED stimulator built in the front, vertically adjustable peak. The device is powered and controlled via USB connection from a standard PC/notebook using custom software for visual stimuli generation and for VEP recording and processing. Up to four electrodes can be placed at any scalp location or in combination with two dry electrodes incorporated into the headset. External visual stimulators, such as a tablet, can be used with synchronization. Feasibility and validation studies were conducted with 86 healthy subjects and 76 neuro-ophthalmological patients including 67 who were during the same session also tested with a conventional VEP system. RESULTS: VEPpeak recordings to standard (pattern-reversal) and non-standard (motion-onset, red-green alternation) were robust and repeatable and obtained also in immobilized patients. Good comparability of results was achieved between VEPpeak and standard examination. Some systematic differences in peak latencies and amplitudes are consistent with differences in stimulus characteristics of the two compared systems. DISCUSSION: VEPpeak provides an inexpensive system for clinical use requiring portability. In addition to ISCEV standard VEP protocols, free choice of stimuli and bio-signal recordings make the device universal for many electrophysiological purposes.

Vision before and after scharioth macular lens implantation in patients with AMD: an electrophysiological study.

BACKGROUND: For patients with age-related macular degeneration (AMD), a special intraocular lens implantation partially compensates for the loss in the central part of the visual field. For six months, we evaluated changes in neurophysiological parameters in patients implanted with a "Scharioth macula lens" (SML; a center near high add + 10 D and peripheral plano carrier bifocal lens designed to be located between the iris and an artificial lens). METHODS: Fourteen patients (5 M, 9 F, 63-87 years) with dry AMD were examined prior to and at 3 days after, as well as 1, 2, and 6 months after, implantation using pattern-reversal, motion-onset, and cognitive evoked potentials, psychophysical tests evaluating distant and near visual acuity, and contrast sensitivity. RESULTS: Near visual acuity without an external aid was significantly better six months after implantation than before implantation (Jaeger table median (lower; upper quartile): 4 (1; 6) vs. 15 (13; 17)). Distant visual acuity was significantly altered between the pre- (0.7 (0.5; 0.8) logMAR) and last postimplantation visits (0.8 (0.7; 0.8) logMAR), which matched prolongation of the P100 peak time (147 (135; 151) ms vs. 161 (141; 166) ms) of 15 arc min pattern-reversal VEPs and N2 peak time (191.5 (186.5; 214.5) ms vs. 205 (187; 218) ms) of peripheral motion-onset VEPs. CONCLUSION: SML implantation significantly improved near vision. We also observed a slight but significant decrease in distant and peripheral vision. The most efficient electrophysiological approach to test patients with SML was the peripheral motion-onset stimulation, which evoked repeatable and readable VEPs.

Visual evoked and event-related brain potentials in HIV-infected adults: a longitudinal study over 2.5 years.

PURPOSE: The aim of this neurophysiological study was to monitor changes in the visual and cognitive function of HIV-infected patients treated with combination antiretroviral therapy. METHODS: Eleven adult Czech HIV+ patients, with a mean age of 35 years and CD4 cell count ≥ 230 × 106 cells/L of blood at the time of enrollment, underwent four to six examinations over the course of 2.5 years to evaluate pattern-reversal and motion-onset visual evoked potentials (P-VEPs and M-VEPs), visually driven oddball event-related potentials (ERPs) and Montreal Cognitive Assessments. In addition to evaluating the intraindividual change in the observed parameters, we also compared patient data to data from eleven age- and gender-matched controls. RESULTS: We did not find any significant differences in P-VEPs between the patients and controls or in the paired comparison of the first and last visit. The only significant finding for P-VEPs was a linear trend in prolongation of the 20' P-VEP P100 peak time. In M-VEPs, we found a significant intergroup difference in the N160 peak time recorded during the first visit for peripheral M-VEPs only. During the last visit, all N160 peak times for patients differed significantly from those of the control group. The only intervisit difference close to the level of significance was for peripheral M-VEPs, which confirmed the trend analysis. No significant differences between patients and controls were found in the ERPs, but the P300 peak time showed a significant difference between the first and last visits, as confirmed by the trend. Patient reaction time was not significantly delayed at the first visit; however, it was prolonged with time, as confirmed by the trend. CONCLUSION: Our aim was to evaluate whether antiretroviral treatment in HIV+ patients is sufficient to preserve brain visual function. The optic nerve and primary visual cortex function tested by the P-VEPs seem to be preserved. The prolongation of the M-VEPs suggests an individually detectable decline in CNS function, but these changes did not show a progression during the follow-up. From a longitudinal perspective, the trends in peak time prolongation of the 20' P-VEP, peripheral M-VEP, ERP and reaction time suggest a faster decline than that caused by aging in healthy populations, as previously described in a cross-sectional study.

Pattern- and motion-related visual evoked potentials in HIV-infected adults.

PURPOSE: The goal of the current study was to explore visual function in virally suppressed HIV patients undergoing combined antiretroviral therapy (cART) by using pattern-reversal and motion-onset visual evoked potentials (VEPs). METHODS: The pattern-reversal and motion-onset VEPs were recorded in 20 adult HIV+ patients with a mean age of 38 years and CD4 cell counts ≥230 × 106 cells/L of blood. RESULTS: Nine out of 20 patients displayed VEP abnormalities. Pattern-reversal VEPs pathology was observed in 20% of subjects, and 45% HIV patients had impaired motion-onset VEPs. Five out of 16 neurologically asymptomatic HIV patients had prolonged motion-onset VEP latencies in both eyes. Four neurologically symptomatic patients displayed simultaneously abnormal motion-onset and pattern-reversal VEP latencies: monocular involvement was observed in two patients with Lyme and cytomegalovirus unilateral optic neuritis. Binocular involvement was noted in two patients with cognitive deficits. Correlation analysis between disease duration, CD4 cell count, HIV copies in plasma, MoCA and electrophysiological parameters did not show any significant relationships. CONCLUSIONS: The functional changes of the visual system in neurologically asymptomatic virally suppressed HIV patients displayed higher motion-onset VEP sensitivity than in standard pattern-reversal VEP examinations. This promising marker, however, has no significant association with clinical conditions. Further exploration is warranted.

Comparison of visual information processing in school-age dyslexics and normal readers via motion-onset visual evoked potentials.

Standard pattern-reversal visual evoked potentials (VEPs) and motion-onset VEPs (M-VEPs) were tested in 19 dyslexics and 19 normal readers aged 7-13 years in order to evaluate the feasibility of M-VEPs for the objective diagnostics of a visual subtype of dyslexia, in which a dysfunction of the magnocellular subsystem/dorsal stream of the visual pathway is suspected. The set of VEPs consisted of the pattern-reversal VEPs with check sizes of 20', two types of translational motion (with low and high contrast) and two types of radial motion (in the full field or the periphery). While the P100 peak parameters in pattern-reversal VEPs did not differ between the group of dyslexics and controls, the group of dyslexics displayed significantly longer N2 latencies in all types of M-VEPs. Abnormal N2 latencies were found in 35-56% of dyslexics in different types of M-VEPs, with translational motion with high contrast being the most sensitive stimulation. A receiver operating characteristic analysis showed that the latencies of M-VEPs displayed higher discrimination potential than M-VEPs amplitudes. The study confirms a "magnocellular pathway/dorsal stream deficit" in approximately half of dyslexics.

Difficulties of motion-onset VEP interpretation in school-age children.

BACKGROUND: In adults, motion-onset visual evoked potentials (M-VEPs) with a dominant N2 peak represent a useful diagnostic tool. However, it is difficult to use this type of VEP in children because of the long maturation (up to 18 years) of M-VEPs, which is characterised by a gradual decrease in N2 peak latency and shape development. Moreover, in some children, M-VEPs are difficult to identify with standard stimuli. METHODS: We tested features of M-VEPs in 30 children (7-12 years) with the following set of standard stimuli used in our lab for examining adults ( https://web.lfhk.cuni.cz/elf ): low-contrast translation motion (TM) and expansion/contraction motion (ExCoM) in full field and in periphery (with central 20° masked). In 16 children, a high-contrast TM was also tested. RESULTS: With standard (low-contrast) stimuli, a common M-VEP to TM and to ExCoM was detected in 77 and 83 % of children, respectively. The M-VEPs to ExCoM in the periphery were detected in only 43 % of children. An abnormal dominant P1 peak was found in 9 % of VEPs to TM, 12 % of VEPs to full-field ExCoM and 14 % of VEPs to peripheral ExCoM. The M-VEPs to all low-contrast stimuli displayed large inter-individual latency variability (N2 peak latency differed for more than 100 ms). High contrast (more suitable for the non-mature magnocellular pathway) shortened M-VEP latencies and improved amplitudes. CONCLUSIONS: Our findings show that the maturation of motion perception in children is inter-individually variable, which limits the diagnostic use of M-VEPs.

Visual mismatch negativity in the dorsal stream is independent of concurrent visual task difficulty.

The manipulation of attention can produce mismatch negativity-like components that are not necessarily connected to the unintentional sensory registration of the violation of probability-based regularity. For clinical purposes, attentional bias should be quantified because it can vary substantially among subjects and can decrease the specificity of the examination. This experiment targets the role of attention in the generation of visual mismatch negativity (vMMN). The visual regularity was generated by a sequence of two radial motions while subjects focused on visual tasks in the central part of the display. Attentional load was systematically varied and had three levels, no-load, easy, and difficult. Rare, deviant, and frequent standard motions were presented with a 10/60 ratio in oddball sequences. Data from 12 subjects was recorded from 64 channels and processed. vMMN was identified within the interval of 142-198 ms. The mean amplitude was evaluated during the aforementioned interval in the parietal and fronto-central regions. A general linear model for repeated measures was applied to the mean amplitude with a three-factor design and showed a significant difference [F (1, 11) = 17.40, p = 0.002] between standard and deviant stimuli and between regions [F (1, 11) = 8.40, p = 0.01]; however, no significant effect of the task [F (2, 22) = 1.26, p = 0.30] was observed. The unintentional detection of irregularity during the processing of the visual motion was independent of the attentional load associated with handling the central visual task. The experiment did not demonstrate an effect of attentional load manipulation on mismatch negativity (MMN) induced by the motion-sequence, which supports the clinical utility of this examination. However, used stimulation paradigm should be further optimized to generate mismatch negativity that is stable enough to be usable not only for group comparisons but also for a single subject assessment.

Spared cognitive processing of visual oddballs despite delayed visual evoked potentials in patient with partial recovery of vision after 53 years of blindness.

We examined the visual and cognitive functions of a 72-year-old subject, KP, who recovered his sight after 53 years of visual deprivation. We used visual evoked potentials (VEPs) to pattern-reversal and motion-onset stimuli and cognitive responses (ERPs) during the oddball paradigm to assess the effect of long-term deprivation on a mature visual system. KP lost his sight at the age of 17 years, and light projection onto his right retina was restored at 71 years by a corneal implant. Nine months after sight recovery we recorded reproducible responses to all examined stimuli. The response to pattern reversal contained two P100-like peaks with the later peak being dominant and significantly delayed (260 ms) when compared to the P100s of two control subjects, to whom the stimuli were adjusted in size and contrast to mimic KP's vision. KP's motion-onset VEPs to full-field and peripheral stimuli had a characteristic shape with a well-defined N2 peak; however, both peaks were significantly delayed (262 and 272 ms) compared to control responses. Unlike the P100 and N2 peaks, which represent sensory detection, the P3b/P300 component of the ERP to a target event in the oddball paradigm was not further delayed. In spite of degraded vision and sensory deprivation lasting 53 years, KP displayed reproducible responses to all reported stimuli. Long-term visual deprivation and retinal detachment degraded KP's visual sensory processing, assessed by pattern-reversal and motion-onset VEPs, whereas the cognitive processing of appropriate visual stimuli was not compromised.

Aging effect in pattern, motion and cognitive visual evoked potentials.

An electrophysiological study on the effect of aging on the visual pathway and various levels of visual information processing (primary cortex, associate visual motion processing cortex and cognitive cortical areas) was performed. We examined visual evoked potentials (VEPs) to pattern-reversal, motion-onset (translation and radial motion) and visual stimuli with a cognitive task (cognitive VEPs - P300 wave) at luminance of 17 cd/m(2). The most significant age-related change in a group of 150 healthy volunteers (15-85 years of age) was the increase in the P300 wave latency (2 ms per 1 year of age). Delays of the motion-onset VEPs (0.47 ms/year in translation and 0.46 ms/year in radial motion) and the pattern-reversal VEPs (0.26 ms/year) and the reductions of their amplitudes with increasing subject age (primarily in P300) were also found to be significant. The amplitude of the motion-onset VEPs to radial motion remained the most constant parameter with increasing age. Age-related changes were stronger in males. Our results indicate that cognitive VEPs, despite larger variability of their parameters, could be a useful criterion for an objective evaluation of the aging processes within the CNS. Possible differences in aging between the motion-processing system and the form-processing system within the visual pathway might be indicated by the more pronounced delay in the motion-onset VEPs and by their preserved size for radial motion (a biologically significant variant of motion) compared to the changes in pattern-reversal VEPs.

Effect of memantine in Alzheimer's disease evaluated by visual-evoked potentials to pattern-reversal, motion-onset, and cognitive stimuli.

The authors tested visual-evoked potentials to pattern-reversal, motion-onset, and visual cognitive event-related potentials in 17 patients with mild-to-moderate Alzheimer's disease treated with Memantine (noncompetitive N-methyl-D-aspartic acid antagonist) to verify whether these objective methods can evaluate its therapeutic effect. The patients were examined before Memantine administration and after 3 and 6 months from the treatment onset. Besides electrophysiology, psychologic Alzheimer Disease Assessment Scale-cognitive part (ADAS-cog) test was also performed. Neither ADAS-cog nor any of the electrophysiological tests were able to prove a significant beneficial effect of Memantine therapy in our group of patients. The results of psychologic and electrophysiological tests did not correlate. An individual improvement of ADAS-cog score (decrease of score by 4 and more points) was present in only 29% of patients, improvement of event-related potentials (shortening of P300 peak latency by at least 20 milliseconds) occurred in 42% of patients. Conversely, in 52% of patients, Memantine therapy led to transitory decline of motion processing (delay of N2 peak latency of the motion-onset visual-evoked potentials by at least 10 milliseconds after the first 3 months of therapy, followed by return to pretherapy values in next 3 months).

Within-session reproducibility of motion-onset VEPs: effect of adaptation/habituation or fatigue on N2 peak amplitude and latency.

We explored the effect of repeated visual stimulation on motion-onset visual evoked potentials (M-VEPs) during 25 min recording sessions in 10 subjects. The aim of the experiment was to determine influence of global motion adaptation (without motion-aftereffect) on intra-individual variability of M-VEPs and to suggest an optimal recording design for clinical examination. In addition to well described middle-time sensory adaptation, we also observed a long-time effect on motion specific N2 peak (155 ms). The N2 peak exhibited a strong relationship between its latency and inter-peak amplitude to the duration of recording in occipito-parietal derivations. In addition to the middle-term adaptation, N2 peak latency was prolonged by 10 ms and amplitude was attenuated by 30% with respect to the start of the experiment. An exponential model was employed to describe the dependency. The model can be used to reduce intra-individual variability during examination. Observed resemblance between the measured electrophysiological values and already published metabolic changes (glucose and oxygen utilization) during brain processing of visual information is discussed.