According to Carol and Richard Eustice on about.com the definition of a TENS unit is:
"TENS" is the acronym for Transcutaneous Electrical Nerve Stimulation. A "TENS unit" is a pocket size, portable, battery-operated device that sends electrical impulses to certain parts of the body to block pain signals.
The electrical currents produced are mild, but can prevent pain messages from being transmitted to the brain and may raise the level of endorphins (natural pain killers produced by the brain).
Those little electrical impulses made my muscles in my lower back feel like a thousand bucks. Indeed- I had less problems going to sleep than I have had in months. Debbie explained at our next meeting that a home unit could be use on any area that was giving me trouble. Two appointments later- she sent me home with this unit. The advantage of this unit is that it is fully portable. I clips on to my belt area and I can wear it any time and any place. It comes with the electrodes, alcohol wipes and a lotion for after so that the glue from the electrodes does not aggravate my skin. In experimenting with it- I have discovered that for the maxmimum benefit I need to hook myself up (with the assistance of my husband) and lay down on a home heating pad. That said- even when the ability to do that is not there- I can use it on my back and hips and walk around normally with some success.
My insurance covers assistive devices 80 %. If I choose to keep this one (and I will) they will automatically send me more electrodes on a regular basis. The electrodes are reuseable several times but then the glue lessens and I won't have to fool around with trying to find them or ordering them once we see how often I go through them. I have found that they work wonderfully on my shoulders as well; indeed the only place I had very limited help with the TENS was on my neck.
I cannot recommend this particular device enough for anyone dealing with chronic pain. It has been a real boon for me in this period between my MTX and the Orencia. If you have the access- talk to a physical therapist about trying one. You may actually find some much sought after relief.