Summary for the Clinician

Pattern ERG

Pattern VEP

Flash VEP

Pattern ERG

Pattern VEP

Flash VEP

Perg Optic Atrophy

Fig. 9.7. Pattern and flash VEPs and pattern ERGs from a normal subject (N) and from right and left eyes of a 9-year-old patient with dominant optic atrophy. Pattern VEPs are abnormal, PERG N95:P50 amplitude ratio is reduced and P50 is of shortened implicit time, consistent with ganglion cell disease (see text for details)

Fig. 9.7. Pattern and flash VEPs and pattern ERGs from a normal subject (N) and from right and left eyes of a 9-year-old patient with dominant optic atrophy. Pattern VEPs are abnormal, PERG N95:P50 amplitude ratio is reduced and P50 is of shortened implicit time, consistent with ganglion cell disease (see text for details)

ing and delay. Flash VEPs may be less severely affected. With chiasmal involvement, the occipital distribution of VEPs from the fellow eye may additionally demonstrate a degree of interhemispheric asymmetry.

The signs and symptoms in craniopharyn-gioma vary greatly depending on the neural structures affected but commonly involve headache, vomiting and visual disturbance [19]. Nystagmus has been reported in some cases. Anterior extension to the optic chiasm can result in bitemporal hemianopia, unilateral temporal hemianopia, papilledema, or unilateral/bilateral decrease in visual acuity. Children are often inattentive to visual loss and formal testing may be required. Monocular pattern VEPs frequently reveal a crossed asymmetry where there is an abnormal distribution over the two hemispheres which reverses on monocular stimulation of the other eye and which is opposite in nature to that seen in the misrouting of albinism. Stimulus parameters are of crucial importance to accurate localisation. In general, use of a large field, large check stimulus gives paradoxical lateralisation [4,34], whereas a small field,small check stimulus gives anatomical lateralisation. Uncrossed asymmetries have also been reported to reflect unilateral post-chiasmal compression [49].

Summary for the Clinician

Familial optic atrophy

• The PERG shows N95 loss that can occur before a VEP abnormality in DOA. PERG P50 component amplitude reduction may occur in severe long-standing disease significant, usually accompanied by a shortening of implicit time

• The PVEP may be markedly delayed and can vary in amplitude from subnormal to undetectable in end-stage disease

9.7 Unexplained Visual Loss in the Normal Child

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