Gelastic seizure with hypothalamic hamartoma: proton magnetic resonance spectrometry and ictal electroencephalographic findings in a 4-year-old girl.

Gelastic seizure is a rare symptom often associated with hypothalamic hamartoma. We present here a 4-year-old girl with gelastic epilepsy caused by hypothalamic hamartoma and report the magnetic resonance spectrometry and electroencephalographic (EEG) findings. At the age of 2 1/2 years, she developed brief, repetitive laughing attacks or mixed attacks with laughing and crying, which were refractory to carbamazepine. An interictal EEG showed intermittent slow waves in the left frontocentral region and sporadic positive sharp waves in the left centroparietal area. Ictal EEG demonstrated dysrhythmic theta activity in the left central area 3 seconds after the onset of laughing. Brain magnetic resonance imaging demonstrated a large sessile mass, isointense to gray matter, in the region of the hypothalamus, suggesting hypothalamic hamartoma. Proton magnetic resonance spectrometry of the hypothalamic hamartoma revealed a significant reduction of the N-acetylaspartate/serum creatinine ratio. The altered chemical shift imaging with magnetic resonance spectrometry in our patient suggests a biochemical abnormality in the tissue of the hypothalamic hamartoma. Moreover, this abnormal function of the hamartoma tissue might be closely related to epileptogenesis because the time difference between the ictal laughter and the subsequent EEG changes in the ictal EEG does not support the idea that the activated cortex is the epileptogenic focus.