And we don't know the cause, we don't know it exactly happens, or if the main thing that's affected is even the brain or the stomach. Vomiting's controlled by the brain, but it has a lot of different causes. Someone who's vomiting violently would usually first be thought to have food poisoning or gastroenteritis. Getting a diagnosis of cyclic vomiting syndrome can be a long drawn out procedure. Tim Tuder again.
People can be quite well in between.
Tim, for example, plays rugby and has his pilot's licence. But he's been in and out of hospital 48 times. Mary Tuder, Tim's mother. Well it got progressively worse and worse and worse. And that went on for months.