Hi Mark,
I have a lp shunt. My case is a bit different than the "usual" IIH, but, I too found that I was getting relief each time I had a LP. It is "logical" that if you do, the longer lasting thing to do is to get a shunt installed. It is up to you and your Docs to decided if it should be lumbar or ventricle. I was too chicken to go for the brain surgery as first try and my Neurosurgeon felt comfortable trying the lumbar first. So we did. So far so good. My body is still getting used to it, so I am experiencing fluctuations. Overall, I feel MUCH better!
In addition to this wonderful website, have you looked at: http://www.iihsupport.org/index.php
They are from across the pond, so much of their references are different, but you can read the experiences of many others who have had surgeries there.