My ate who works as a bouncer in a big club in melb CBD said that he once had to attend to a guy having a seizure on the dance floor. His friends said that he had just been drinking and took a strong pill (he was still a bit of a newbie), anyway he ended up being alright but was very very messy after the seizure, eyes rolled into back of his head, couldn't stand, constant vomitting. I guess with a case like this you can't be sure it was MDMA that casued the seizure, he could have taken other drugs (ie. GHB), had an underlying medical condtion (like epilepsy) or had an adulterated pill.
I think I read somewhere that you can have a seizure like experience if you have serotonin syndrome after having an extrmely high dose of MDxx, doesn't sound fun either way.