How common is shunt independence (for vp shunts) how does it happen? examples of such cases? what's the chance for hydro acquired after tumor removal?

Complex issue: A vp shunt is a device to bypass the usual drainage pathways of the brain. Tumors, malformations, and infections can cause blockage of normal pathways that result in a need for placement of a vp shunt. Usually the shunt will have to remain in place and functional or severe pressure can develop. On occasion alternative drainage develops so that the shunt in not longer working but better to stay.

Rarely useful: Theoretically, shunt independence can happen, and I have seen a few patients who may no longer need their shunt. Practically, it is rarely worth thinking about. There is no foolproof way to know if a shunt is still flowing or not. Even if the shunt is draining one drop per day, removing it would lead to return of hydrocephalus, so it's rarely worth trying, and usually best to leave it alone.