A TENS unit consists of a central power source which is shaped like a small box that looks like a beeper. The box contains controls that modulate the intensity, frequency, and waveform of the current. Connected to the central power source are lead wires. Attached to the lead wires at the other end are electrodes that are self-adhesive and applied directly to the skin. The electrodes are designed to conduct the current from the central power source to the skin.



To use the TENS, the lead wires are connected to the central power. Electrodes are then attached to the lead wires at the other end and then applied to the affected area of the body. Once the TENS is set up, the TENS unit is turned on. The patient will sense the current which is increased to the point where it is felt to be comfortable. The patient should leave the TENS at that setting. During the day, the body accommodates to the electrical stimulus and the patient may be tempted to increase the current intensity. That should not be done because, prolonged intense electrical stimulus can lead to muscle fatigue and rebound pain!

TENS current can be adjusted for waveform, current level, and frequency. The medical person, either a physician or physical therapist, should instruct the patient as to the best setting for their individual case. TENS frequencies below 10 Hz are termed low frequency. Frequencies higher than 50Hz are called conventional or high frequency TENS.

The ability to change frequencies, duration of therapy, waveforms, and intensity makes TENS a versatile tool in pain management.

TENS is used to ameliorate pain related to a number of conditions seen in a rheumatology office. These include: chronic low back pain, osteoarthritis, chronic neck pain, and fibromyalgia. TENS is covered by most insurances including Medicare.

Studies regarding the effectiveness of TENS for different conditions have been, in the past, flawed by poor study design. However, in recent years, the ability to adequately blind the patient and the examiner have yielded some excellent studies showing the effectiveness of TENS in both relieving pain as well as in reducing the amount of pain medication a patient may require.

This latter benefit is particularly important when it is realized that TENS is an extremely safe treatment modality with virtually no side effects.

How does TENS work? There are a few theories that explain the effectiveness of TENS. The first is the gate theory. This is the oldest explanation. According to this theory, application of electrical stimulus to peripheral nerves sends signals to the spinal cord and these signals block the transmission of pain signals by the spinal cord. In essence, this theory is similar to that offered as an explanation for the effectiveness of acupuncture. Indeed, the low frequency form of TENS has been used as a type of ?electrical acupuncture.?

Studies of high frequency TENS has demonstrated that levels of glutamate and aspartate (chemicals that may induce pain) are reduced in the spinal cord. Low frequency TENS increases serotonin and endorphin levels within the central nervous system thereby reducing pain.

The effectiveness of TENS has been demonstrated in at least two trials demonstrating equivalency of TENS against non-steroidal anti-inflammatory drugs in osteoarthritis of the knee.

TENS can be used as a single therapeutic modality or in combination with other treatments including medicines.

The demonstration of effectiveness compared with anti-inflammatory medicines as well as its possible ability to decrease the amount of analgesics and narcotics a patient may require is an obvious benefit. Because of these many advantages, TENS is an attractive treatment modality for use in the rheumatology office.