We report the case of a 41 year-old woman with a slight mental retardation and epilepsy. MRI showed a diffuse subependymal heterotopia. The cognitive level supports the view that the ectopic cells are probably not important for the normal cortical functions but that they are likely able to maintain some of the electric properties of normal neurons, even if with altered discharge modalities. The genetic etiology of subependymal neuronal migration disorders is discussed. This is the second reported case of diffuse subependymal heterotopia in a female patient.
