Experimentally induced disorders of neuronal migration produce an increased propensity for electrographic seizures in rats.

Disorders of neuronal migration in humans are associated with intractable epilepsy and some evidence suggests a causal relationship. This study evaluated electroencephalograms (EEG) of rats with experimentally induced disorders of neuronal migration. Fetal Sprague-Dawley rats were exposed to 196 cGy external irradiation on days 16 and 17 of gestation. This produced adult offspring with diffuse cortical dysplasias, agenesis of the corpus callosum, periventricular heterotopias, and dispersion of the pyramidal cell layer of the hippocampus. Epidural electrodes were implanted in four experimental (irradiated on gestational day 17) and four control rats. EEGs were recorded without anesthesia and in the presence of the anesthetic agents ketamine, acepromazine, and xylazine. In the presence of acepromazine, xylazine, or a combination of the two drugs, two of the four experimental rats had prolonged ictal activity on EEG. In one of the rats the ictal activity progressed to electrographic status epilepticus. Ketamine alone did not produce ictal EEG activity. None of the control rats demonstrated ictal activity under any treatment condition. This study demonstrates that disorders of neuronal migration are associated with an increased propensity for seizures in the presence of certain sedating agents.