Muscle twitches and spasms anywhere in the body (even eye twitches) can be the result of magnesium deficiency. This is very common in people with mercury poisoning because mercury interferes with the body's ability to utilize magnesium. Constipation, anxiety, fatigue and headaches are other magnesium-deficiency symptoms that are common in mercury toxic individuals.

I've also read, but have not fully confirmed, that magnesium deficiency can contribute to the accumulation of toxic metals such as mercury in the brain. Hence, magnesium helps to protect the body against heavy metal toxicity.

I know I used to experience a lot of leg cramps, muscle aches and pain, stiff neck, headaches and constipation before I had my amalgams removed.

Even though I've had my amalgams removed, I take extra magnesium, since I still have mercury in my tissues. The research I've done indicates that magnesium citrate and magnesium malate are two of the best forms of magnesium supplements to get, as they are better absorbed than the common magnesium oxide. Here's some information on the magnesium I use: Magnesium Complex

Hope this helps!