Abstract
Purpose Examine visual acuity and visual evoked potentials (VEP) in humans with cortical migration defects (polymicrogyria or PMG). Methods Five infants with PMG (0.4–1.6 yrs age) were compared to 5 age matched controls. PMG was documented via multiple MRI sequences. Acuity was assessed Teller acuity cards. VEPs were recorded across the occiput to reversing checks and onset of sinewavegratings. VEP epochs were examined for amplitude/phase coherency at 16 harmonics. Results For infants with PMG, all had microcephaly, 2 had diffuse polymicrogyria, 1 had bilateral parietal involvement, 1 with right parietal-frontal and 1 with bilateral parietal-temporal. Three infants had normal acuity; 2 had no visual tracking. VEP lateralization was seen in infants with polymicrogyria confined to one hemisphere. All subjects had amplitude/phase coherency with systematic phase shifts with increasing frequency. Coherency could be detected in infants with PMG and no visual behaviors; however the time domain VEP was abnormal. Selecting epochs with stronger coherency at one harmonic had the similar effects across harmonics indicating coherency of across frequency bands. Selective averaging of epochs with phase coherency improved VEP amplitudes 337% in PMG and 60% in controls. Conclusions Reproducible and large amplitude VEPs can be recorded from infants with polymicrogyria and no visual behaviors.
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