Multifocal VEP in children: its maturation and clinical application

Abstract

Aim: To study the maturation of multifocal visual evoked potentials (multifocal VEP) in normal children between the ages of 5 and 16 years and to apply the results clinically in selected cases to the diagnosis of optic pathway diseases.

Method: 70 normal children were recruited from the community and multifocal VEP (Accumap ObjectiVision, Sydney, Australia) was recorded. The waveform of the evoked responses, the latency and amplitude were analysed. Using these data, an age matched comparison was made with three children with advanced optic nerve disease; two had optic nerve glioma and one had congenital glaucoma.

Results: The full field amplitude did not correlate with age and varied greatly within each age group (coefficient of variability 28%). When scaled with respect to the background electroencephalogram the intra-age group variability decreased to 15% and a sigmoid relation was found between amplitude and age. The scaled amplitude remained largely unchanged till 11 years, between 11 and 13 years there was a rapid increase (40%), and remained stable thereafter. This relation was seen at all eccentricities tested. The latency decreased gradually with age and plateaued at 13 years. In the three children with vision abnormalities this test was able to detect scotomas consistent with their condition.

Conclusion: Multifocal VEP perimetry shows an age related maturation in the visual pathway, characterised by distinctive timeframe of development for amplitude and latency. It can be performed by children as young as 5 years of age and holds promise as a diagnostic test capable of documenting children's visual fields objectively, even before they are able to perform subjective field tests.

Figure 1

Photograph of a 10 year old child performing the test.

Figure 2

Left eye combined topographic map recorded from a 6 year old child using four channel recording. Upward deflections on the traces represent positive peaks.

Figure 3

Fourier power spectrum of background EEG of a 6 year old child.

Figure 4

Multifocal VEP traces of the superior and inferior hemifields from the vertical channel. Traces shown are example of VEP with best signal to noise ratio. Vertical and horizontal scales represent 100 nV and 100 ms respectively. Upward deflections on the traces represent positive peaks.

Figure 5

Hemifield latency with age.

Figure 6

(A) Scatter plot of full field amplitude and age. (B) Scatter plot of linear correlation between EEG Fourier power and age. (C) Scatter plot of age and full field amplitude scaled with respect to background EEG Fourier power. Fitted with a sigmoid curve. (D) Plot of normalised amplitude at different eccentricities with age. The age groups of 5–7, 8–10, 11–13, 14–16 years, contained 15, 26, 14, 15 children respectively.

Figure 7

Multifocal VEP recording of a 6 year old child with optic nerve glioma involving the left optic nerve and chiasm, who was unable to perform subjective perimetry. (A) The right and left eye multifocal VEP traces and the age matched comparisons are shown. (B) The scotoma was reproduced on repeat testing.

Figure 8

Multifocal VEP recording of an 11 year old child with post-resection of an optic nerve glioma involving her right optic nerve and chiasm. Her visual acuity was 6/12 in the left eye and she was unable to perceive light with the right eye.

Figure 9

(A) Subjective field results of an 11 year old child with glaucoma secondary to Sturge-Weber syndrome. (B) Multifocal VEP recordings from the same child, showing a superior field defect on the inter-eye asymmetry deviation plot.