"Epilepsy."
They had been at Hogwarts for a week, and Draco was visiting Snape, who continued to inhabit the dungeons despite his change in status to headmaster. Surprisingly, the students had seemed subdued, fearful, and resentful, but none had exhibited a true rebellion. Yet. Not even Harry Potter.
Snape looked up from his study of his cup of tea.
"Epilepsy," Draco repeated. "It's got to be. It matches the symptoms of Granger. Seizures. Incurable. Muggle. She must have developed in as a child. Although how she never seized in school before until seventh year, or it never spread beyond the Gryffindor House, escapes me."
Snape glanced moodily at the fire. "You are correct, Draco. Epilepsy was my estimate as well, and I took the liberty of perusing…Dumbledore's files on Miss Granger. She did develop it as a young child, but the seizures were rare and small, and she took medicine to suppress it. She requested, among other things, to hide her condition from her peers. Not even the teachers know, except Professor McGonagall."
"So why…"
"Why now? Why do her friends suddenly know and look like veterans when dealing with a seizure?" At Draco's nod, he answered his own questions. "I believe, if my spy in the Order was not lying, that Miss Granger has been researching a way to treat her condition or cure it better than the muggles have. Judging from the unfamiliar potion her friends got to her, she has at least succeeded in treating the seizures when they are taking place, if not cure the cause of them. It is a neurological mishap, overloading the brain with too many electrical impulses. You do remember the celebrations this summer when Miss Granger's parents were…eliminated, do you not?" Yes, Draco did. He listened raptly. "I was there. I did not do anything, but Bellatrix did crucio Miss Granger several times before she managed to do a summoning spell and have us fleeing from the Order."
Draco's mind whirled. "Cruciatus…didn't you have me research that as a fifth year? It is a curse that targets the nervous system, and the brai-" his eyes widened.
Snape nodded. "Yes. Cruciatus targets both the nervous system, stimulating the hot and cold impulses erratically to cause pain, as well as the neurons of the brain. That is why the curse causes trembling not unlike a seizure. I expect that experiencing the curse only aggravated her condition. The muggles still don't know entirely what causes it, or how to stop it completely. I'm sure you've read that a person seizing for too long will eventually either die or cause brain damage. You can guess what happened at the Longbottoms some years ago, then."
Draco gulped.