When do asymmetrical full-field pattern reversal visual evoked potentials indicate visual pathway dysfunction in children?
Our study aimed to find out the association between full-field pattern reversal visual evoked potential (pVEP) transoccipital asymmetries and half-field pVEP transoccipital distributions in children. Over a six-month period, 46 patients (mean age: 9 years 9 months) had both monocular full-field and half-field pVEPs to test checks subtending 50 min of arc in a 35 degree full-field and 0-17.5 degree lateral half-field. Silver-silver chloride electrodes placed at Oz, O1 and O2 were referred to Fz. Monocular full-field data were categorised according to the degree of transoccipital asymmetry. Half-field data were measured and summated to see whether they explained any full-field asymmetry. In this cohort of 46 patients, eight (17%) patients had symmetrically distributed monocular full-field pVEPs for each eye. Four of these patients had normal half-field pVEP distributions for each eye, but the other four showed a half-field deficit in one or both eyes. Of the 38 patients with asymmetrically distributed full-field pVEPs in at least one eye, 17 (44%) patients showed a half-field deficit, 20 (53%) showed responsive, but symmetrically distributed half-field responses, and one patient (3%) showed typical half-field distributions. Half-field pVEPs can help explain full-field asymmetries and should be attempted in any child able to co-operate with testing and in whom visual pathway dysfunction is suspected.
Clinical and Academic Department of Ophthalmology, Great Ormond Street Hospital for Children, London, UK.
Tessa B
TB
Mellow
Alki
A
Liasis
Ruth
R
Lyons
Dorothy
D
Thompson
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D009778:Occipital Lobe / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time; D012189:Retrospective Studies; D014786:Vision Disorders / Q000503:physiopathology*; D015349:Vision, Monocular / Q000502:physiology; D014794:Visual Fields; D014795:Visual Pathways / Q000503:physiopathology*