Pachygyria (HP_0001302) is a malformation of cortical development with abnormally wide gyri with sulci 1,5-3 cm apart and abnormally thick cortex measuring more than 5 mm (radiological definition). See also neuropathological definitions for 2-, 3-, and 4-layered lissencephaly. Also known as: Cerebral pachygyria, Fewer and broader ridges in brain, Macrogyria.