you are experiencing this!
This is very similar to many of the symptoms I am having.
I had initially experienced some relief with Slow-Mag. I'd experienced more relief with Zanaflex, added to the slow Mag (not taken at the same time.)
My doctor now wants me to try more Zanaflex, as I was using this only at night. (Zanaflex can be used up to three time daily, according to your doctor's recommendations.)
I do not know the cause, specifically, in my case. We are still in the midst of testing. However, I do have a significant amount of peripheral neuropathy, showing slowing of nerve conduction in all limbs.
In my own experience, this gets worse...the twitches and cramps (along with incredible muscle weakness), when I am exposed to heat. I get much worse once ambient air temp goes over 67 degrees farenheit and remains there for any period of time.
I wish I could be of more help!
MrsD has a really good thread on magnesium in the vitamins/supplements forum. I do not feel qualified to comment on magnesium dosages. I will tell you that I have had excellent luck with the "Slow Mag" formulation (magnesium chloride)... when considering the various formulations I have tried over the years and more recently.
I am feeling pretty useless when it comes to be helpful to you at the moment!
I hope someone with more knowledge will come along!
Please take exceptional care!