Although transcutaneous electrical nerve stimulation (TENS) is not strictly speaking acupuncture, there is a good deal of overlapping with acupuncture and probably some common ground in the ways they work. TENS is primarily used for the relief of pain although it can be used in other circumstances also. TENS machines put out pulsed current at rates of about 15 to 150 Hz through electrodes. The optimal rate is usually around 80 Hz. Other variables are the duration of the pulse (fixed in many machines), the amplitude of the current, and of course the placement of the electrodes. Electrodes are usually placed (a) on either side of the painful area, (b) over a main nerve leading to the painful area, (c) on the spine one or two spinal segments above the affected dermatome, or (d) over TPs.
It’s important to make sure that patients give TENS a proper trial and understand clearly how to use the machine. They must be able to feel the stimulation, which causes a tingling feeling which, however, is usually felt only at one of the two electrodes. The nervous system adapts quickly to the stimulus and therefore the amplitude of the current has to be increased after a few minutes’ use.
Acupuncture and TENS are to a certain extent interchangeable, but some patients who respond to acupuncture don’t respond to TENS and vice versa. TENS can be tried for any kind of pain, including low back pain back pain, osteoarthritis, post-herpetic neuralgia, peripheral nerve injury, phantom limb pain, stump pain and unexplained abdominal pain. It and non-invasive. However, it generally gives relief only as long as it is switched on, and patients have to be prepared to buy the machine (currently about £100) since there is no NHS means of supplying them.
TENS should be avoided in patients with a demand pacemaker implanted because of the theoretical danger that it could trigger the pacemaker, and electrodes should not be placed over the carotid sinus because of the possibility of raising blood pressure. A few patients become sensitized to the rubber of which the electrodes are generally made; various new kinds of electrodes are now available, at increased cost.