Abnormality of neuronal migration Gray matter heterotopia SNOMEDCT_US:128490007 Gray matter heterotopias Neuronal heterotopia Heterotopia Gray matter heterotopia is caused by clumps of gray 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 gray matter within the white matter, and the term gray matter heterotopia is more frequently used. 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. Grey matter heterotopia Heterotopias UMLS:C0008519 Grey matter heterotopias SNOMEDCT_US:416286003 SNOMEDCT_US:417338002