Well, there is no simple answer to your question, Rach!

The ice pack test does show improvement in MGers, but it's not a reliable "definitive" test for MG. That's why they suggest further testing.

My digging revealed some conflicting evidence, and makes me realize that this heat/cold effect on MG is not so simple.

http://www.ncbi.nlm.nih.gov/pubmed/3614664

http://pmj.bmj.com/content/76/893/162.full

http://www.scielo.br/scielo.php?pid=...pt=sci_arttext

In this article it states, "The physiological theory behind the test is very simple; it is thought that by cooling the tissues, and more specifically the skeletal muscle fibres, the activity of the acetylcholinesterases are inhibited (laboratory data suggest below 28°C)."

http://shr.sagepub.com/content/1/1/14.full

And it goes on to say, "This simplistic theory may not be the only factor involved in the resolution of the ptosis; some studies have concluded that it may not be simply cold that can produce a positive ice pack test and that heat can produce similar results, almost certainly by the same physiological effect."

And this brings up the issue of heat and cold making MG better or worse. The say that cold inhibits acetylcholinesterase and, therefore, creates more localized acetylcholine.

Other articles have stated that heat and cold increase acetylcholinesterase in the body, thereby reducing acetylcholine and making MG worse.

http://www.ncbi.nlm.nih.gov/pubmed/1959652

And, curiously, what happens in corn to AChE and ACh.

http://www.ncbi.nlm.nih.gov/pubmed/21757255

And a more scientific article on heat stress mechanisms.

http://jap.physiology.org/content/93/6/1947

That article is an eye opener. The body uses acetylcholine in the mechanisms to modulate cutaneous vasodilation when the body becomes heated up. Maybe. Why aren't there more accurate and definitive studies on this?

So what does heat do to MG? Does it use up more ACh because ACh is busy doing other "tasks" in the body other than keeping our muscles strong?

And do people with more nitric oxide or better nitric oxide use fair better in the heat and cold (i.e., Abby)? I'm also wondering how MGers who take NSAIDS do out in the cold/heat. Do prostaglandins also play a role?

And what does cold do to the body? Does acetylcholine rush in to the cold area due to vasoconstriction?

Does acetylcholine regulate vasodilation and vasoconstriction in the body?

It's all mediated by nitric oxide (NO) and prostaglandins (PG).

http://jap.physiology.org/content/98/2/629

Stay with me here. This is not a simple topic, Rach!

Could POTS be caused by a NO or PG regulation error in vasodilation/vasoconstriction?!!!

And then I found this.

http://www.ncbi.nlm.nih.gov/pubmed/21642500

http://jaha.ahajournals.org/content/3/1/e000755.full

I'd like to do more digging, but I'm worn out. There's a definite connection here between acetylcholine and POTS.

Is the ice pack test definitive for MG? No. But it is a strong sign of MG.

The neurologists in the UK apparently don't want to do the testing necessary to figure out if you have MG or CMS. I find that to be reprehensible and unethical.

Does any of this help or do you now have a mammoth sized headache?


Annie