I'd check with the stem cell people! Most definitely.
The question for you, Tyson, who is planning on a very specialized medical treatment still in the "study" stage, is to avoid anything that can interfere with the study, and your response to the agents used there. If you were not participating in the study at all, then the question then revolves around pain relief potential and other issues that revolve around medical MJ use.

Marijuana has an extremely long half life. Once you start using regularly it can take many months to leave your system.
http://alcoholism.about.com/od/pot/a/marijuana_test.htm

Study parameters on medical treatments are very strict in what they will allow the participants to do, eat, or consume. MJ is still considered a "recreational" drug... it is fat soluble and may be in the bone marrow.

Numbness/tingling in hands and feet are signs of neuropathy IMO. They may occur with impaired glucose tolerance, or from certain toxic drugs. Neuropathy in diabetics starts before the actual blood glucose becomes seriously deranged. This article explains the development of neuropathy during pre-diabetes:
http://www.citeulike.org/user/wrs1/article/6499468
Most neuropathy starts in the distal parts of the body, hands and feet and then progresses toward the trunk. It is not uncommon for doctors to dismiss it. Or even misdiagnose it, as we know very well at the PN forum.

In some cases, numbness and tingling signal mitochondrial damage. If this becomes longer term, the mitochondria in the nerve cells may die and the neuropathy becomes permanent. This happens in certain forms of poisoning (arsenic and thallium) and also with Chemo and toxic drug ingestion, pesticides and solvents.

This is a general link for people with beginning neuropathies. The drug list is only a sample, of the long list of agents that can damage nerves.
http://www.nlm.nih.gov/medlineplus/e...cle/000700.htm