Serial EEG and sleep polygraphic studies on lissencephaly (agyria-pachygyria)

We carried out serial EEG studies on 12 cases of lissencephaly (6 of agyria and 6 of pachygyria), polysomnograms being recorded in 8 of the 12 cases. Fourteen Hz sleep spindles appeared from early infancy in all cases. They were poorly observed after the age of 1 year, and 5-11 Hz high-amplitude rhythmic activity (HARA) of more than 300 microV appeared predominantly in place of the 14 Hz spindles. Both the 14 Hz spindles and HARA showed asymmetry, but the dominant cerebral area for both types of waves was much the same. Four of the 6 agyria cases showed hypsarrhythmia within the first 6 months after birth, 3 of the 4 cases showing asymmetric hypsarrhythmia at first. Their hypsarrhythmia consisted of very high-voltage 5-7 Hz slow sharp waves and delta waves. The EEG abnormalities transformed from hypsarrhythmia to focal spikes in the 6 pachygyria cases. The polygraphic study on 8 cases revealed that the proportion of REM sleep decreased in 3 cases and the REMs/min values decreased in 7. Infantile spasms occurred in 4 of the 8 cases. The REM/min values decreased in all of these 4 cases, and, furthermore, the proportion of REM sleep decreased in 3 of the 4 cases. These findings suggest that lissencephaly involves a disorder of the brainstem, and that the combination of brainstem lesions and severe cerebral dysplasia is important for the manifestation of infantile spasms in lissencephaly.