Abstract
Purpose:
Examine visual acuity, visual evoked potentials (VEP) and oculomotor performance with neuroimaging in children with cortical migration defects (polymicrogyria or PMG).
Methods:
Fifteen children with PMG (0.4 - 4 yrs age) were compared to age matched controls. PMG was documented by MRI (T1, inversion recovery, T2, FLAIR, diffusion and gradient echo sequences). Acuity was assessed Teller acuity cards and converted to age corrected log minimum angle of resolution (logMAR). Pattern VEPs were recorded to reversing checks and onset-offset of sinewave gratings.
Results:
PMG was bilateral in all children but had varied involvement of the fronto-parietal and temporal lobes. Nine of 15 children had PMG involvement that included the occipital lobe. All had developmental delay, neurologic deficits, or seizures. At presentation, age-corrected visual acuity was normal in 5 (33%) children ( 20/40 or better Snellen equivalent for age) and was mildly to severely reduced in the remaining 10 children (average 20/200 Snellen equivalent for age). Average visual acuity was not significantly different between children with and without involvement of the occipital lobe (log MAR 0.8 vs 0.7, respectively; p = 0.49). Two infants without visual behaviors had a detectable VEP response. Children with PMG involving the occipital lobe had significantly lower VEP amplitude and signal-to-noise ratios compared to children without occipital lobe involvement. Three of 3 children with CMV related PMG had normal visual acuity and preserved VEP responses despite significant MRI abnormalities. Visual acuity did not significantly improve with age in 9 children at last follow-up.
Conclusions:
All children with PMG had measurable visual function. Two children with no visual behaviors had reproducible VEPs indicating a defect in sensorimotor transformation. Three of 5 children with normal visual acuity had CMV related PMG. Visual acuity cannot be predicted by the presence of PMG in the occipital lobe.