I just re-read you post. One thing that could also be wrong with your grandfather, he might be having some TIA (mini strokes) These can definitely be helped with drugs and other medically measures.
I hope he feels better soon.
Hello~It sounds to me like he has some pinched nerves in his lower and upper back, this will certainly cause the needles and pins sensations. It can also cause twitching.
Unfortunately, no medicine will help, oh, it will help with the pain, but what he probably needs is a few chiropractic adjustments. If they run some tests on him and they don't find any thing wrong, I highly suggest making an appointment with one, I think a few treatments will help ease his issues.