Incidentally, I know of a few people, friends of my parents, that have gotten a shunt for NPH. They suffered from one of the 3 "W" symptoms of NPH, wet, wobbly, wackiness, that you're certainly aware of.
One had a dramatic improvement very quickly, where one or more of the Ws was resolved. Another had the spinal tap indicating she was a good candidate, but the shunt is still not resolving all the issues even after 2 months.
Do you have any clinical experience with the success rates of the shunt?