Five of fifteen children with histologically proven neuronal migration disorders (NMD) and refractory localization-related epilepsy had surface positive spikes or sharp waves or both on scalp EEG performed preoperatively in a study at The Hospital for Sick Children, Toronto, Canada. Patients with positive epileptiform discharges had earlier onset of seizures with focal motor pattern, poor response to AEDs, a higher frequency of hemiparesis preoperatively, and surgery at a younger age with poor outcome. Lesions involving the rolandic fissure are more extended than those seen on the MRI and cannot be completely resected. [1]

COMMENT. Compared to the usual negative polarity of most epileptiform abnormalities, focal positive spike waves encountered with neuronal migration disorders are predictive of more extensive lesions, higher incidence of hemiparesis, focal motor seizures refractory to AEDs, and less favorable surgical outcome associated with incomplete resection.

The pathomechanism of the neuronal migration disorder seen in Miller-Dieker syndrome (smooth cerebral surface and four layered thickened cortex) was investigated using specific antibodies against the protein product of LIS-1, the gene responsible for MDS phenotype, at the National Center of Neurology and Psychiatry, Kodaira, Tokyo [2]. Loss of LIS-1 immunoreactivity occurred in brains with MDS, but not with isolated lissencephaly, holoprosencephaly, Fukuyama-type congenital muscular dystrophy, and Zellweger syndrome. Loss of LIS-1 gene product is specific to the abnormal neuronal migration in Miller-Dieker syndrome.