31 December 2009

TENS confusion

Given that TENS was part of the discovery of the gate-control theory 40 years ago, it really would be nice if its implications for the distinction between nociception and pain had seeped in. This is from a press release on Science Daily:
Widely used device for pain therapy not recommended for chronic low back pain A new guideline issued by the American Academy of Neurology finds that transcutaneous electric nerve stimulation (TENS), a widely used pain therapy involving a portable device, is not recommended to treat chronic low-back pain that has persisted for three months or longer because research shows it is not effective.... TENS can be effective in treating diabetic nerve pain, also called diabetic neuropathy, but more and better research is needed to compare TENS to other treatments for this type of pain. Research on TENS for chronic low-back pain has produced conflicting results. For the guideline, the authors reviewed all of the evidence for low-back pain lasting three months or longer. Acute low-back pain was not studied. The studies to date show that TENS does not help with chronic low-back pain.

So far so good. But then in the nickel summary of what TENS is they write:
With TENS, a portable, pocket-sized unit applies a mild electrical current to the nerves through electrodes. TENS has been used for pain relief in various disorders for years. Researchers do not know how TENS may provide relief for pain. One theory is that nerves can only carry one signal at a time. The TENS stimulation may confuse the brain and block the real pain signal from getting through.

How about:
Neural signals reporting injury have to pass through a gate in the spine in order to be transmitted to the brain and cause pain. The electric impulse from TENS closes the gate.

That's still inaccurate. But it at least avoids framing the phenomenon as the system stopping the pain before it gets to the brain. Getting people used to distinguishing between nociception and pain is a small but important step in a better public understanding of analgesia and chronic pain conditions.