Based on a review of the litterature and a detailed longitudinal single case study of a child with early onset gelastic seizures and hypothalamic hamartoma, the authors review the arguments suggesting that the acquired cognitive and behavioral symptoms seen in the majority of cases of this special epileptic syndrome result from a direct effect of the seizures. The early neurobehavioral profile of the case presented in this paper and that of a previous study is particular and combines features of a pervasive developmental and an attention deficit disorder which are probably closely related to the particular location of the epilepsy and its spread from the hypothalamus.