lissencephaly ("smooth brain") is the extreme form of pachygyria. in lissencephaly, few or no sulci are seen on the cortical surface, resulting in a broad, smooth appearance to the entire brain. lissencephaly can be radiologically confused with polymicrogyria, particularly with low-resolution imaging, but the smoothness and lack of irregularity in the gray-white junction, along with markedly increased cortical thickness, distinguishes lissencephaly.