Fits of laughter (gelastic epilepsy) with a tumour of the floor of the third ventricle. A video tape analysis.

A patient with fits of laughter due to a tumorous alteration (hyperplasia) of the floor of the third ventricle is described with electroencephalographic findings indicative of focal epilepsy (complex partial seizures = psychomotor fits). The laughter is interpreted as an inborn emotional expression with structural substrate in the hypothalamus and neighboring brain. With structures remaining intact functional disorders in this area can cause epileptic phenomena with participation of the limbic system.