Neuronal migration disorders presenting with mild clinical symptoms.

Two children with neuronal migration disorders and unexpectedly mild clinical symptoms are reported. The first patient was followed with the diagnosis of febrile convulsion and seizures associated with fever for 14 years. Computed tomography scans were normal. Although periodic slow waves of the left parietal cortex were detected on the first two electroencephalograms, his latest examination was normal. Magnetic resonance imaging performed at 16 years of age disclosed a left parietal schizencephaly extending between the parietal cortex and corpus callosum. The second patient was followed with the diagnosis of febrile convulsion for 2 years and later experienced afebrile seizures. On his latest visit, a posterior parietal pachygyric region and a parieto-occipital island heterotopia on the left hemisphere were diagnosed by magnetic resonance imaging. We believe that review of these patients, at the mildest end of the clinical spectrum of neural migration disorders, will contribute to a new understanding of the correlation between clinical and pathologic findings of neuronal migration disorders.