EEG is a test that detects electrical activity in the brain using small, metal discs (electrodes) attached to the scalp.  The brain is constantly sending electrical signals even while sleeping.  Because the HH is deep within the brain, far away from the scalp EEG electrodes, the EEG may not detect any abnormal activity during a seizure.  This is especially true for gelastic (laughing) seizures.

Back to Glossary Index Page