Hypothalamic hamartomas and ictal laughter: evolution of a characteristic epileptic syndrome and diagnostic value of magnetic resonance imaging.

Detailed study of 4 patients and review of the literature allowed us to delineate further the epileptic syndrome associated with hypothalamic hamartomas, which characteristically begins in infancy with laughing seizures. Because early childhood psychomotor development is usually normal, the condition appears benign and may not even be recognized. The episodes of laughter are brief, frequent, and mechanical in nature. These features distinguish it from other forms of epileptic laughter, particularly that which occurs in temporal lobe epilepsy. Subsequently, the seizures become longer, other seizure types appear, and between the ages of 4 and 10 years, the clinical and electroencephalographic features of secondary generalized epilepsy develop. Cognitive deterioration occurs and severe behavior problems are frequent. Prognosis for seizure control and social adjustment is poor. Cortical abnormality occurs in association with the hypothalamic hamartoma. The lesions are best detected by magnetic resonance imaging but may be difficult to identify by computed tomographic scanning.