Periventricular heterotopia (HP_0007165) can be described as follows. A form of gray matter heterotopia were the mislocalized gray matter is typically located periventricularly, also sometimes called subependymal heterotopia. Periventricular means beside the ventricles. This is by far the most common location for heterotopia. Subependymal heterotopia present in a wide array of variations. There can be a small single node or a large number of nodes, can exist on either or both sides of the brain at any point along the higher ventricle margins, can be small or large, single or multiple, and can form a small node or a large wavy or curved mass. Also known as: Periventricular gray matter heterotopia, Periventricular grey matter heterotopia, Periventricular neuronal heterotopia, Subependymal gray matter heterotopia, Subependymal grey matter heterotopia, Subependymal neuronal heterotopia.