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A. H. Weiss, J. O. Phillips, J. P. Kelly; Visual Cortical Function in Infants With Polymicrogyria. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5889.
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© ARVO (1962-2015); The Authors (2016-present)
Polymicrogyria is a brain malformation characterized by abnormal cortical organization. The purpose of this study was to assess visual processing in infants with polymicrogyria using behavioral measures of visual acuity, visual evoked potentials and eye movements.
Subjects were 5 term infants (2-12 mo of age at initial evaluation). Polymicrogyria was confirmed by MRI (Siemens) performed at 1.5 or 3T. Binocular acuity was assessed with Teller acuity cards. Transient VEPs were recorded with a 5 channel montage to an array of stimuli including 163’-84’reversing checks and onset-offset of 0.5 -2 cycle/degree gratings. Conjugate eye movements were recorded using binocular video-oculography (2 subjects).
All infants were developmentally delayed and 4 of 5 had microcephaly. The ocular fundi were normal in all but one child, who had mild optic nerve pallor. Two infants with unilateral hemispheric polymicrogyria had normal acuity for age, robust VEPs with interhemispheric asymmetry and normal conjugate eye movements. One infant with bilateral perisylvian polymicrogyria and one infant with diffuse generalized polymicrogyria had no visual orienting behaviors and VEPs were large but delayed and waveforms were distorted. Both infants had no visually guided eye movements but reflexive eye movements (VOR & OKN) were elicited. One infant with bilateral frontal and parietal polymicrogyria and cerebellar hypoplasia had reduced acuity and VEPs were large, latencies were normal but waveforms were distorted. A 60-90 diopter esotropia was present and tracking was saccadic. Postnatal improvements in acuity and VEPs were seen in infants tested longitudinally.
Reproducible and large amplitude VEPs of normal or prolonged latency can be recorded from infants with polymicrogyria sparing the occipital cortex. The broad temporal tuning of the VEP response may represent a loss of higher cortical feedback that shapes the VEP waveform. A normal VEP at the midline with asymmetrical distribution of the potential across the occiput is associated with unilateral hemispheric polymicrogyria. In the presence of a recordable VEP, the lack of volitional eye movements is consistent with a defect in sensorimotor transformation.
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