Dr. John Holter is the man credited with creating the first silicone valve.
He was a machinist who's son, born in 1955 developed hydrocephalus and needed a shunt.
Unfortunately his shunt wasn't ready for his own son. By the time it was, his son had so many complications from the earlier shunts that when he did receive a Holter valve he
did well for 14 months and then he died anyway.
It's to bad this book is out of print as it contains a lot of good information.