ERGs on the brain: the benefits of simultaneous flash retinal and cortical responses in paediatric cerebral visual impairment

Dorothy A Thompson,Alki Liasis,Sian E Handley,Katrina L Prise

doi:10.1007/s10633-018-9631-4

Dorothy A Thompson, Alki Liasis + Show 2 more

Open Access

https://doi.org/10.1007/s10633-018-9631-4

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Abstract

PurposeTo highlight the importance of simultaneous flash electroretinogram (ERG) and visual evoked potential (VEP) recording to differentiate a true flash VEP response from an artefact caused by the intrusion of the ERG on a mid-frontal reference electrode in cases of severe cerebral visual impairment (CVI).MethodsWe report an observational case series of four children with severe CVI who underwent simultaneous flash ERG and VEP recordings. Flash VEPs from Oz–Fz and lower lid skin ERGs referred to Fz were recorded simultaneously to Grass intensity setting 4 flash stimulation.ResultsIn all cases, atypical, but reproducible VEPs were evident. Comparison of the timing and waveform of the VEPs and ERGs showed the occipital responses were inverted ERGs and no true flash VEP was evident.ConclusionsWhile ISCEV and neurophysiology standards do not require the simultaneous recording of the flash ERG with the VEP, these cases highlight the usefulness of this non-invasive technique particularly in suspected paediatric cerebral visual impairment to differentiate a true VEP from an artefact caused by ERG contamination.

Highlights

In children with severe cerebral visual impairment (CVI), behavioural measures of visual function are rarely obtainable
Of the flash ERG with the visual evoked potential (VEP), these cases highlight the usefulness of this non-invasive technique in suspected paediatric cerebral visual impairment to differentiate a true VEP from an artefact caused by ERG contamination
We retrospectively identified four children with severe CVI seen within the last year of our clinical practice at the Tony Kriss Visual Electrophysiology Unit, Great Ormond Street Hospital for Children, London, UK, in whom an artefact was evident in the flash VEP making it difficult to identify a true response

Summary

Introduction

In children with severe cerebral visual impairment (CVI), behavioural measures of visual function are rarely obtainable. Visual evoked potentials (VEPs) have become a well-recognised and valuable tool in the assessment of visual pathway function in these children. Pattern VEPs are able to provide an indication of macular pathway function and an estimate of visual potential [1]. In the absence of pattern VEPs, flash VEPs are able to provide a measure of generalised post-retinal activation and determine the presence or absence of chiasmal/hemisphere dysfunction. In children with CVI, identifying the presence or absence of visual pathway activation to the striate cortex has consequences upon the type of support and rehabilitation the patient receives and on their longer-term quality of life [2].

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