The EEGs and evoked potentials were studied in 21 Dutch patients with lissencephaly type I at the Departments of Clinical Neurophysiology and Neurology, Juliana Children’s Hospital, The Hague, The Netherlands. Compared to patients with atypical cortical dysplasia and to a control group the EEGs in the lissencephaly patients showed the following patterns significantly more often: (a) generalized fast activity (8-18/s) with an amplitude higher than 50 μV, (b) sharp- and slow-wave complexes with high amplitude (range 500 - 3000μV and (c) an alternating pattern consisting of bursts of sharp waves alternating with periods of electrocerebral depression. Short latency somatosensory evoked potentials in 10 patients after stimulation of the median nerve were abnormal. 
COMMENT. Lissencephaly may be differentiated from an atypical cortical dysplasia by CT and/or MRI. In addition, the EEG and evoked potentials may be of diagnostic value. Generalized fast activity and sharp- and slow-wave complexes were noted in 20 of the 21 lissencephaly patients and in only 1 of the 21 patients with atypical cortical dysplasia. An abnormal PET scan suggested the microscopic pathology confirmed at autopsy in an infant with lissencephaly and normal gross cortical structure. The clinical features were intractable seizures and developmental delay but normal head growth . Radiographic and clinical variability within the 3 subtypes of lissencephaly are reviewed in 19 patients ages 1 day to 6 years.