Hey hydro-wife,
I had a shunt put in place when I was a couple days old (which has been replaced a few times) and doesn't need to be adjusted or dialed such as your husband's case - yet I too have experienced episodes where the area around my shunt and face has become slightly numb and then fades away. I have not talked with a doctor about this, but the last time I did go in to talk to my doctor about a shunt concern I was told that anything short of intense headaches and the obvious symptoms of a shunt malfunction were usually harmless, so I assume the numbness is fairly benign. I would be interested to hear the results of your trip if you do go into the doctor about this though.
Durgal