When doctors suggest TENS therapy
to help control a painful condition, they are not suggesting you calm down by
counting backwards from ten. It is way
of using a very minor amount of electrical current for the reduction of pain
There is nothing new to the idea of
using electricity to reduce the sensation of pain. In ancient Greece both Aristotle and Plato
remark on the “Black Torpedo”, an electric ray fish whose shocks were administered
for the relief of pain.
During the 1800’s, dentists had
started to experiment with electrical devices for pain control. By the 1900’s a huge variety of electrical
devices were available to treat everything from impotency to depression.
In 1965, the Gate Control Theory of
pain was proposed, which described how sensation could shut the “gate” on pain
perception. This theory explained why
since the dawn of time mothers have been blowing kisses on skinned knees – the
sensation of the blowing reduces the perception of pain. This theory also helps to explain how electrical
sensation can alter the perception of pain.
It was soon discovered that
electrical stimulation of the skin around an area of injury could relieve
pain. These devices quickly gave rise to
transcutaneous (meaning through the skin) electrical nerve stimulators – TENS.
TENS is typically used to treat
both recent and long term pain conditions.
Frequently, a TENS device will be prescribed to help reduce
post-surgical pain. TENS’ greatest
strengths are that it is completely drug-free, not habit forming, and virtually
TENS blocks the sensation of pain
at the spinal cord before the information reaches the brain. This is accomplished by grouping electrode
pads around the area of pain and administering a low-volt electrical current.
The electrical current delivered by the pads penetrates the skin only deep
enough to reach the nerve fibres.
For most individuals, it takes
roughly 30 minutes for TENS treatment to relieve pain. Some conditions require use of TENS for
several hours at a time for ongoing relief of pain.
The small size of the TENS units
makes them very portable so people can wear the units while still going about
their usual daily activities. Usually
these units are the size of a pack of cigarettes and are worn on the belt.
Depending on the TENS current
frequency (high or low), different types of pain nerves will be affected. This means TENS can block the sensation of
pain by manipulating the nervous system in two different ways.
One way is to select a frequency
that stimulates nerves that block other nerves from transmitting pain to the
spinal cord. A second mechanism is to
use a frequency that stimulates the body to release pain relieving chemicals
called endorphins. The TENS treatment
feels like a tingling, or slight pins and needles.
Although TENS can safely be used on
a daily basis for weeks at a time, it is most likely not appropriate for
long-term use. It appears that over time,
the nervous system starts to learn to accommodate for the TENS, reducing its
effectiveness. Eventually the nervous
system learns to cancel out the noise of the TENS sensation, which means pain
is felt again.
Like any treatment there is a wide
range in how much benefit each person derives from it.
TENS is most valuable for treating
pain from the musculoskeletal system.
So, TENS would be something to try for post-knee surgery pain or for an
episode of low back pain. However, it
would be poor choice to treat the pain associated with a stomach cramp.
There are a few minor risks
associated with TENS. For instance, it should not be used if you have poor
sensation, if you are pregnant, over a tumour or if you have a pacemaker. It
should never be used around the heart, on the head or over breast tissue. There
is also a minor risk of skin irritation, but this is rare.
A TENS unit can usually be
purchased for around $50. Your health
care provider can help you to determine where to place the pads and the best settings
for your TENS unit.
Dr. Jemal Khan is a chiropractor based in the Cayman Islands.