[Epilepsy with laughing seizures, hypothalamic hamartoma and precocious puberty. Contributions of MRI, computed EEG topography (CET) and ambulatory EEG (A-EEG)].

The concurrence of gelastic (laughing) seizures, hypothalamic hamartoma and precocious puberty constitutes a well defined epileptic syndrome in children; moreover mental retardation, neuropsychological deterioration and behavioral disorders have been often observed in these patients. In two cases we studied by means of MRI the appearance and the site of the hamartoma (in the posterior part of the hypothalamus with extension toward the third ventricle). The EEG study was performed by means of repeated recordings, of Computed EEG Topography (CET) and of Ambulatory EEG (A-EEG): in both patients during interictal periods paroxysmal EEG discharges prevailing in temporal or fronto-temporal regions and slight abnormalities of the background activity in the same areas were detected. Laughing seizures were recorded in each patient particularly by means of A-EEG: in case 1 bursts of high-voltage activity ("theta" waves) followed by depression of the background rhythm and by irregular spike discharges located in left temporal region were observed; in patient 2 irregular generalised spike discharges followed by slow waves or by depression of the background activity were seen. The presence of local abnormalities in both patients can support the hypothesis that the cortex, especially of the temporal anterior lobe, is involved in the origin of the laughing seizures. The significance of the mechanisms of secondary generalization as regards the seriousness of the epilepsy and of the mental impairment in these patients is also suggested.