Magnesium deficiency can cause muscle twitching and involuntary muscle contractions (clonus).
This article, "The Importance of Magnesium to Human Nutrition," by Michael Schachter M.D., is very informative.
http://www.mbschachter.com/importance_of_magnesium_to_human.htm
(If the url is removed, you can google for the name of the article and the author.)
It's also possible that your granddaughter's twitching is a tic, in which case the magnesium will also be helpful.
Wishing you the best,
Carol
Hello Dear,
You should consult a neurologist and go in for EEG tests to know the electrical activity of the brain.Also a CT scan should be done to know any pathology.Unless all the neurological investigations are done,the diagnosis cannot be confirmed.
Best