Abnormal movement-related cortical potential in patients with subcortical heterotopia.

Movement-related cortical potential (MRCP) is recorded to investigate the cerebral motor preparation in two patients with subcortical heterotopia. Magnetic resonance imaging (MRI) studies were conducted in the two patients. Scalp MRCP elicited by self-paced voluntary extension of the wrist was recorded. The MRCP waveforms and the potential maps were compared to those of an age-matched normal subject. MRI reveals subcortical heterotopia in the right frontal area and bilateral centrum semiovale in one patient and in the left parietal lobe in the other. Both of the patients had history of early onset epilepsy and were hypersensitive to unexpected loud noises. Distinctly different from the normal MRCP, the waveforms of the patients are flattened in all scalp electrodes by moving either the right or the left hand. And the topographic potential map detects no evidence of preponderance of negativity on the hemisphere contralateral to the moving side in the patients. The ectopic neurons of the subcortical heterotopia may produce chaotic discharges, which can interrupt or cancel the well oriented dipole of the MRCP activities.