Why does increased intracranial pressure cause projectile vomiting?

Not sure: Increased pressure in the brain/skull is often associated with vomiting. We don't know exactly how the pressure triggers the vomiting center in the brainstem, it just does. Since sudden onset of headache and vomiting can be a sign of a serious condition see you doctor immediately. This is especially true if the vomiting occurs during the night while sleeping.

Unclear: Vomiting and increased intracranial pressure (icp) go hand in hand. Why increased pressure is related to vomiting is unclear. Hydrocephalus, bleeding, and tumor can cause pressure changes resulting in vomiting. Increased pressure from a brain tumor can cause vomiting that even mimics an eating disorder and must be distinguished.