Neurosurgeons suggest that patients with normal pressure hydrocephalus should not fly.  There may be circumstances that vary from case to case, but in general it is not something that they recommend.  Flying is too unpredictable and if the cabin were to lose pressure, the person with this affliction would have serious consequences.  If you have to fly to a certain destination to have the shunt procedure, it seems that you should get the neurosurgeons opinion about this problem.  There may be safer ways to travel to this destination, or perhaps some sort of medical transportation could be arranged for you and the patient.  Putting the person at risk, when they are already in need of a procedure, does not seem to be the best way to proceed.  Investigate every option, and get the advice of more then one physician before you take this risk.