The reproducibility of binocular pattern reversal visual evoked potentials: a single subject design

Visual Evoked Potentials for the Detection of Diabetic Retinal Neuropathy

Visual evoked potentials (VEP) are visually evoked signals that extract electroencephalographic activity in the visual cortex that can detect retinal ganglion cells, optic nerves, chiasmal and retrochiasmal dysfunction, including optic radiations, and the occipital cortex. Because diabetes causes diabetic retinopathy due to microangiopathy and neuropathy due to metabolic abnormalities and intraneural blood flow disorders, assessment of diabetic visual pathway impairment using VEP has been attempted. In this review, evidence on the attempts to assess the visual pathway dysfunction due to abnormal blood glucose levels using VEP is presented. Previous studies have provided significant evidence that VEP can functionally detect antecedent neuropathy before fundus examination. The detailed correlations between VEP waveforms and disease duration, HbA1c, glycemic control, and short-term increases and decreases in blood glucose levels are evaluated. VEP may be useful for predicting postoperative prognosis and evaluating visual function before surgery for diabetic retinopathy. Further controlled studies with larger cohorts are needed to establish a more detailed relationship between diabetes mellitus and VEP.

A novel system for measuring visual potentials evoked by passive head-mounted display stimulators

PURPOSE

The objective of this work is to evaluate the performances of a novel integrated device, based on passive head-mounted display (HMD), for the pattern reversal visual evoked potential (PR-VEP) clinical test.

METHODS

Google Cardboard® is used as passive HMD to generate the checkerboard pattern stimuli through an Android® application. Electroencephalographic signals are retrieved and processed over 20 subjects, 12 females and 8 males between 20 and 26 years. Morphological PR-VEPs and frequency response were compared with previous literature results, to test the reproducibility and the efficacy of the proposed solution.

RESULTS

PR-VEPs evoked by our novel prototype showed typical triphasic waveforms in moderate agreement with those obtained with other more expensive HMDs and standard commercial devices. Statistical analysis did not highlight strong differences among the systems over the features analyzed except for the P100 amplitude and peak time (**p < 0.005).

CONCLUSION

The proposed solution opens the door for a new generation of non-invasive first-level diagnostic devices of optic nerve pathologies inexpensive and easy to access.

Clinical electrophysiology of the optic nerve and retinal ganglion cells

Clinical electrophysiological assessment of optic nerve and retinal ganglion cell function can be performed using the Pattern Electroretinogram (PERG), Visual Evoked Potential (VEP) and the Photopic Negative Response (PhNR) amongst other more specialised techniques. In this review, we describe these electrophysiological techniques and their application in diseases affecting the optic nerve and retinal ganglion cells with the exception of glaucoma. The disease groups discussed include hereditary, compressive, toxic/nutritional, traumatic, vascular, inflammatory and intracranial causes for optic nerve or retinal ganglion cell dysfunction. The benefits of objective, electrophysiological measurement of the retinal ganglion cells and optic nerve are discussed, as are their applications in clinical diagnosis of disease, determining prognosis, monitoring progression and response to novel therapies.

Giant pattern VEPs in children

Our aim is to elaborate the clinical significance of giant amplitude pattern reversal visual evoked potentials (VEPs) in children. 'Giant' amplitude VEPs exceed the upper 97.5^th centile, 90% CI for age. We scrutinised 2750 pattern VEPs recorded to international standards between Jan 2015 and 2017 from children aged 16 years and under, attending a specialist children's hospital. Twenty seven children, median age 6yrs, (range 1-16 yrs), were identified with giant VEPs (P100 amplitude range 65-163 μV). Most, 22/27 (81%), had conditions associated with a risk of raised ICP. Sixteen of these twenty two children had craniosynostosis; six multi-sutural and eight single suture disease. Others had Idiopathic Intracranial Hypertension, arachnoid cyst, NF1 with shunted hydrocephalus, chronic infantile neurological cutaneous and articular (CINCA) syndrome, nephrotic cystinosis and obstructive sleep apnoea. Five children presented with a range of conditions, some associated with seizures some symptomatic, but as yet undiagnosed. Frequent structural associations were optical coherence tomography measures of optic disc maximum anterior axial horizontal retinal thickness projection >160 μm and neuro-radiological findings of CSF effacement and copper beaten appearance. Ultrasonography measures of optic nerve sheath diameters varied, but in one child took 2 years to resolve after treatment for raised ICP. Optic disc gradings by fundoscopy were mostly normal, as were visual acuities. Raised ICP was confirmed by gold standard ICP bolt measurements in five of seven children tested. These data suggest that rICP should be considered if a child has sustained giant amplitude VEPs at normal latency.

Developmental Effects on Pattern Visual Evoked Potentials Characterized by Principal Component Analysis

Purpose

Peak amplitude and peak latency in the pattern reversal visual evoked potential (prVEP) vary with maturation. We considered that principal component analysis (PCA) may be used to describe age-related variation over the entire prVEP time course and provide a means of modeling and removing variation due to developmental age.

Methods

PrVEP was recorded from 155 healthy subjects ages 11 to 19 years at two time points. We created a model of the prVEP by identifying principal components (PCs) that explained >95% of the variance in a “training” dataset of 40 subjects. We examined the ability of the PCs to explain variance in an age- and sex-matched “validation” dataset (n = 40) and calculated the intrasubject reliability of the PC coefficients between the two time points. We explored the effect of subject age and sex upon the PC coefficients.

Results

Seven PCs accounted for 96.0% of the variability of the training dataset and 90.5% of the variability in the validation dataset with good within-subject reliability across time points (R > 0.7 for all PCs). The PCA model revealed narrowing and amplitude reduction of the P100 peak with maturation, and a broader and smaller P100 peak in male subjects compared to female subjects.

Conclusions

PCA is a generalizable, reliable, and unbiased method of analyzing prVEP. The PCA model revealed changes across maturation and biological sex not fully described by standard peak analysis.

Translational Relevance

We describe a novel application of PCA to characterize developmental changes of prVEP in youths that can be used to compare healthy and pathologic pediatric cohorts.

Serial, Visually-Evoked Potentials for the Assessment of Visual Function in Patients with Craniosynostosis

This study aimed to evaluate the effect of craniofacial surgical intervention on the visual pathway's function by comparing pre- to post-operative patterned, visually-evoked potentials (pVEP). A retrospective review was conducted on craniosynostosis patients who had pre- and post-craniofacial surgery pVEP testing. The pVEP measured grade in terms of amplitude latency and morphology of the waveforms. The pre- and post-operative results were compared. The study identified 63 patients (mean age at preoperative pVEP of 16.9 months). Preoperatively, 33 patients (52.4%) had abnormal pVEP. Nine patients had evidence of intracranial hypertension, and of those, eight (88.9%) had abnormal pVEP. Within 6 months postoperatively, 24 of 33 patients (72.7%) with abnormal preoperative pVEP developed normal postoperative pVEP, while all 30 patients with normal preoperative VEP maintained their normal results postoperatively. Significant improvements in pVEP latency in patients with broad or delayed latency waveforms was evident for subjects with preoperative grades 2-4 (grade 2, p = 0.015; grade 3, p = 0.029; grade 4; p = 0.007), while significant postoperative increase in amplitude was significant for patients with abnormally low amplitude grade 3 and 5 waveforms (grade 3, p = 0.011; grade 5, p = 0.029). Serial pVEP testing represents a useful tool for the early detection of visual pathway dysfunction and follow up visual pathway function in craniosynostosis. Surgical intervention for craniosynostosis can result in the reversal of preoperative pVEP abnormalities seen in these patients, resulting in the normalization of the pVEP waveform, amplitude and latency, depending on the preoperative pVEP abnormality.

The clinical value of the multi-channel PVEP and PERG in the diagnosis and management of the patient with pituitary adenoma: a case report

Purpose

To present a patient with a diagnosis of pituitary adenoma and progressive visual pathway dysfunction detected in the electrophysiological tests in one-year follow-up. Patient is a 59-year-old male with a non-secreting pituitary macroadenoma.

Methods

Routine ophthalmological evaluation, standard automatic perimetry (SAP), retinal nerve fibers layer and the ganglion cell complex thickness in optical coherent tomography (OCT), as well as electrophysiological examinations (pattern electroretinogram—PERG, multi-channel pattern visual evoked potentials—multi-channel PVEPs record according to ISCEV standards) were performed. The examination and additional tests were conducted 3 times (in 0, 6 and 12 months) and 6 months after neurosurgery.

Results

Visual acuity, funduscopic examinations, SAP, OCT and electrophysiological test results at the first visit were all normal. In both eyes, the abnormalities were observed only in the multi-channel PVEP and PERG despite the absence of the changes in the routine ophthalmological examination and additional tests after 6- and 12-month follow-up. The tumor growth but without chiasmal compression was confirmed by magnetic resonance imaging. The progression of the optic pathway dysfunction in the electrophysiological tests was a cause of surgical removal of the pituitary tumor.

Conclusion

This case highlights novel observations that in patients with pituitary tumor, detection of the early dysfunction of the visual pathway may lead to modification of the medical treatment regimen and reduce the incidence of irreversible optic nerve damage.

Sport-related concussion and sensory function in young adults

CONTEXT

The long-term implications of concussive injuries for brain and cognitive health represent a growing concern in the public consciousness. As such, identifying measures sensitive to the subtle yet persistent effects of concussive injuries is warranted.

OBJECTIVE

To investigate how concussion sustained early in life influences visual processing in young adults. We predicted that young adults with a history of concussion would show decreased sensory processing, as noted by a reduction in P1 event-related potential component amplitude.

DESIGN

Cross-sectional study.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Thirty-six adults (18 with a history of concussion, 18 controls) between the ages of 20 and 28 years completed a pattern-reversal visual evoked potential task while event-related potentials were recorded.

MAIN OUTCOME MEASURE(S)

The groups did not differ in any demographic variables (all P values > .05), yet those with a concussive history exhibited reduced P1 amplitude compared with the control participants (P = .05).

CONCLUSIONS

These results suggest that concussion history has a negative effect on visual processing in young adults. Further, upper-level neurocognitive deficits associated with concussion may, in part, result from less efficient downstream sensory capture.

Spontaneous ocular and neurologic deficits in transgenic mouse models of multiple sclerosis and noninvasive investigative modalities: a review

Multiple sclerosis (MS) is an autoimmune, inflammatory, neurodegenerative, demyelinating disease of the central nervous system, predominantly involving myelinated neurons of the brain, spinal cord, and optic nerve. Optic neuritis is frequently associated with MS and often precedes other neurologic deficits associated with MS. A large number of patients experience visual defects and have abnormalities concomitant with neurologic abnormalities. Transgenic mice manifesting spontaneous neurologic and ocular disease are unique models that have revolutionized the study of MS. Spontaneous experimental autoimmune encephalomyelitis (sEAE) presents with spontaneous onset of demyelination, without the need of an injectable immunogen. This review highlights the various models of sEAE, their disease characteristics, and applicability for future research. The study of optic neuropathy and neurologic manifestations of demyelination in sEAE will expand our understanding of the pathophysiological mechanisms underlying MS. Early and precise diagnosis of MS with different noninvasive methods has opened new avenues in managing symptoms, reducing morbidity, and limiting disease burden. This review discusses the spectrum of available noninvasive techniques, such as electrophysiological and behavioral assessment, optical coherence tomography, scanning laser polarimetry, confocal scanning laser ophthalmoscopy, pupillometry, magnetic resonance imaging, positron emission tomography, gait, and cardiovascular monitoring, and their clinical relevance.