Neuronal migration disorders (NMDs) are a group of disorders caused by the abnormal migration of nerve cells (neurons) very early in the development of the fetal nervous system. Neuronal migration is the process in which neurons move from their place of origin to their permanent location. When this process is disrupted, the result is a structurally abnormal brain involving the cerebral hemispheres, cerebellum, brainstem, and/or hippocampus (NINDS, 2002).
A group of rare neurological disorders in which embryological development of the central nervous system is flawed, resulting in structural abnormalities of the brain. Developmental delays, mental retardation, movement and muscle disorders, and seizures are common consequences.