Late-onset isolated gelastic epilepsy secondary to entrapment of the right temporal horn

The case is reported of a 70 year-old woman with isolated gelastic seizures (GS) secondary to a rare form of focal obstructive hydrocephalus, called entrapment of the lateral horn. Laughing attacks started five years after conservative intracranial surgery for a giant basilar aneurysm. Serial neuro-imaging studies revealed a progressive cystic enlargement of the right temporal horn, damaging the baso-lateral temporal cortex. An ictal EEG recording confirmed the epileptic nature of laughing attacks, and showed that the epileptiform activity originated in the right temporal lobe. Complete seizure control was achieved with current doses of diphenilhydantoin. Analysis of this and other previously reported cases, indicate that symptomatic GS may originate in multiple sites of both cerebral hemispheres, although related to the limbic system. The fact that this case exhibited isolated GS stresses the importance of the baso-lateral temporal cortex in the genesis of this type of seizures.