The patterns of clinical presentation, evolution of the epilepsy, and electoclinical diagnostic features of hypothalamic hamartoma (HH) in 19 patients (8 children and 11 adults), seen between 1991 and 2001, were evaluated at Kings College Hospital and the Institute of Epileptology, London, UK. Of 16 with early-onset epilepsy, 15 had gelastic seizures, and epilepsy began between 0 and 5 years (mean, 2.1 years) in 14, one having infantile spasms in infancy. Precocious puberty (PP) developed in 6, and learning disability in 12. MRI was diagnostic in all. In 8 older patients in the early-onset group, HH was diagnosed between 19 and 54 years (mean, 33 years). Gelastic seizures disappeared in 2, or were reduced to “an urge to laugh” in adolescence and young adulthood. They were replaced by multiple seizure types and evolved into mainly complex partial epilepsy (5 of 8 adults), tonic seizures, or symptomatic generalized epilepsy with atypical absences, drop attacks, and secondarily generalized seizures with cognitive impairment (3 of 8 adults). Of 3 adult-onset patients, only one had gelastic seizures manifested by inappropriate smiling but no laughing, epilepsy was mild, and cognition normal. Of 14 patients with intrahypothalamic hamartomas, all had moderate to severe gelastic epilepsy, 5 had PP, and 13 had early onset epilepsy, whereas of 5 with parahypothalamic hamartomas, only 2 had gelastic seizures, and 3 had late-onset epilepsy. The larger the HH, the greater the number of seizure types associated. Minimally invasive stereotactic thermocoagulation appeared to be superior to open surgical resection of the HH in less severe cases. 
COMMENT. Gelastic seizures are the rule with hypothalamic hamartoma (HH) and early-onset epilepsy, but they frequently evolve into other and milder types of epilepsy in adolescence and adulthood. In adult-onset epilepsy with HH, gelastic seizures are less frequent and milder, and epilepsy is often of the complex partial, tonic, or atypical absence types. Cognitive and behavioral disorders are less frequent in adult-onset cases of epilepsy with HH.