a TENS unit might help, but the head and face are probably not places where you want to be sticking electrodes for the TENS. (the information for my mom's TENS unit that I stole from her in desperation earlier this summer said something about that)

The TENS worked pretty good for the burning skin on my legs and in my ribs.

At physical therapy I took earlier this summer, they had a machine similar to a TENS that they used on my back for back pain that also had MS numbness going on in the same area too. My back was completely numb when they started it, and about 5 weeks later, I could finally feel it. They also had a (more powerful than my mom's) TENS unit they used when they were working on my back and my shoulder. That way they could use their big machine on one spot, and their fancy TENS on the other spot.