Malformed Cerebral Hemispheres By Stephen J Falchek, MD, Nemours / Alfred I duPont Hospital for Children Reviewed / Revised Dec 2018 | Modified Sep 2022 View Patient Education Topic Resources Polymicrogyria with Septo-Optic... Cerebral hemispheres may be large, small, or asymmetric; the gyri may be absent, unusually large, or multiple and small.