i have never heard of bipolar causing anything but rapid mood cycling,, often meds have nasty side effects, but nothing like what you are describing...

sounds like you need a brain specialist of some kind, if not a pscyhiatrist, who will almost certainly be biased in favor of " Trying a Psych MED",, at least some one who will order a brain scan,, ?? i'm no med student or anything, just been around a while,,

good luck with getting your sister to seek out the help she needs~! and best wishes with your son... Gus