Gray matter heterotopia true SNOMEDCT_US:128490007 Gray matter heterotopias MSH:D002828 Neuronal heterotopia Heterotopia Gray matter heterotopia is caused by clumps of grey matter being located in the wrong part of the brain. It is characterized as a type of cortical malformation. The neurons in heterotopia may appear to be normal, except for their mislocation; nuclear studies have shown glucose metabolism equal to that of normally positioned gray matter. The condition causes a variety of symptoms, but usually includes some degree of epilepsy or recurring seizures, and often affects the brain's ability to function on higher levels. Symptoms range from nonexistent to profound, in which case heterotopia can result in severe seizure disorder, loss of motor skills, and mental retardation. Neuronal heterotopia consists of grey matter within the white matter, and the term grey matter heterotopia is more frequently used. Grey matter heterotopia is a malformation of cortical development, where cortical cells (grey matter) are present in inappropriate locations in the brain, due to interruption in their migration to their correct location in the cerebral cortex. Grey matter heterotopia may be unilateral or bilateral, singular or multiple, separate or contiguous. HP:0002281 HP:0002282 HP:0007314 Heterotopia or neuronal heterotopia are macroscopic clusters of misplaced neurons (gray matter), most often situated along the ventricular walls or within the subcortical white matter. human_phenotype Grey matter heterotopia Heterotopias UMLS:C0008519 SNOMEDCT_US:416286003 SNOMEDCT_US:417338002 Malformations of Cortical Development