label: 4-layered lissencephaly
label_lc: 4-layered lissencephaly
description: A form of lissencephaly in which the cortex is thickened and has four more or less disorganized layers rather than six normal layers resulting from incomplete neuronal migration during brain development. At neuropathological examination, a 4-layered cortex consists of an upper molecular layer, a second thin cellular layer containing pyramidal neurons usually observed in layer V, a third pale poorly cellular layer and a fourth thick deep layer made up of neurons which had failed to migrate. Radiologocally would manifest as agyria or pachygyria with cortical thickness greater than 10 mm.