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[|Human|] Two days ago I had an eeg and I almost passed out during the 3 minute hypervetilating breathing stage of the test. I have been for more than a year dizzy and sometimes I have passed out. What does it mean when I pass out during the eeg while lying down? I normally have syncope while standing. They were able to induce it while I was lying down and that surprised me. I see the neurologist on nov. 20. YYYY@YYYY
[|AI|]  Hello! Thank you for asking on Chat Doctor! I understand your concern, and would explain that your symptoms seem to be related to epileptic seizures. You should know that hyperventilation is one of the EEG techniques (besides photostimulation), to induce excitability of the brain cells and gain more information on the brain cell work under extreme conditions. Hyperventilation causes a decrease in partial CO2 pressure on the brain cells, which induces an excitability of the brain cells and even seizures. This episode should be coupled with pathological paroxysmal activity in the EEG in order to confirm the epileptic activity of the brain cells, responsible for the fainting. So it is very probable that your syncope may be related to seizures. I recommend also performing a head up tilt test, to rule in/out a possible orthostatic hypotension, which could be responsible for some of your syncope while standing (not related to the seizures). Hope to have been helpful! Best regards,