hi i had a abdominal shunt fitted in 2005. i suffered severe headaches and sight lose. i was told i had BIH. after considderable time i was offered the shunt. it was ok for awhile but then i noticed that after being busy on my feet all day, when i laughed to much, coughed, or even breaking wind would cause the most severe headaches worse than pre shunt the only way to relieve the pain is to lay flat on my back. most painkillers dont come close . is this due to the shunt.