so I think you are referring to idiopathic intracranial hypertension (old term was psuedotumor cerebri). Our child has congenital hydrocephalus but has a lot of high pressure issues. getting outside the comfort zone of the exceptional surgeon which is very unsettling.

Make sure your dad is seen at a super well regarded facility, go through US News and World Report hospital rankings in neurosurgery & neurology or if there's a IIH patient focused organization then contact them about who to see within a reasonable travel range.

you don't say if your dad had programmable valves or if he really had over draining, so it's a bit hard to be more specific... but... if over draining, there are a few things they could have done with programmable valves and fixed valves in series, potential is there for a cmvp shunt system if it's a pressure problem like fringe numbers of hydrocephalus patients get (that acts a lot like iih from all I can tell). The downside of LP valve systems is potential for chiari but less so with a programmable, pretty common approach with adults last I knew. the big downside for va shunts is infection, those are starting to be really uncommon considering but there are always some unique situations where it is completely appropriate. still, the surgeon suggesting such better be a someone who knows all the ins and outs.

have they ever done icp monitoring? are you at a well respected facility?