I know this is an old thread but You could have easily been talking about my almost four year old child. She has hydrocephalus and was shunted at about 11 months old. About the age of 2 years old she started getting headaches a couple times a month. Some she would just cry that her head hurt, other she would scream in pain and vomit. Each of these would last a few hours then she was fine. We looked for answers for over a year. Finally after switching doctors (ped's not NS) for a third time we got answers. My daughter was diagnosed with Cyclic vomiting syndrome , We soon were off to the neurologist. She now takes a migraine medicine on a daily basis and her cycles have decreased to 1 or 2 every six months.