Résumé
This is the report of a hydranenecephalic child with severe generalized seizures of the Lennox-Gastaut Syndrome (LGS) who lacked the development of the entire cerebral hemispheres and had preserved the brain stem, cerebellum, hypothalamus and a portion of the thalamus as evidenced by radiological and/or physiological studies. Conventional polygraphic sleep studies in these patients showed presence of scalp EEG and other peripheral, somatic and vegetative signs characterizing the wakefulness, quiet sleep and active sleep stages. Absence of the vertex waves and disrupted sleep spindles were the major qualitative EEG abnormalities. In contrast, quantitative abnormalities in duration, latency and number of sleep cycles found in this patient were similar to those found in other children with Idiopathic Lennox-Gastaut Syndrome (ILGS). A substantial reduction in the number of interictal EEG spikes and a shortening of the ictal clonic EEG activities without concomitant EMG jerks were the most distinct epileptiform abnormalities in this child. In contrast, his basic polygraphic patterns of the tonic and apneic seizures were similar to those found in other children with ILGS. Data obtained from this child suggest that both the sleep stages and the generalized seizures of the ILGS basically depend more on the integrity of the brain stem than on the telecephalic structures