Hello -
I think that you likely mean a "TENS" unit which stands for
trans-epidermal nerve stimulation. TENS goes back about 30 years and
is the principal non-pharmacologic treatment modality for pain. The
principle types of pain treated by TENS are neurogenic pain - that is,
pain originating from disorders involving the nerves and chronic pain.
Neurogenic pain can result from central (ie within the brain) causes
like a stroke or MS, or from peripheral causes, like nerve injury,
diabetes or other peripheral neuropathies:
http://www.iasp-pain.org/PCU94c.html
http://216.239.39.104/search?q=cache:BXq5RaZfXnoJ:www.mssociety.org.uk/docs/Pain%2520with%2520refs.doc+tens+pain+neurogenic&hl=en&ie=UTF-8
Chronic pain results in alterations in the manner in which pain is
perceived by the nerves. TENS units has shown some success in the
treatment of chronic pain conditions such as low back pain:
http://www.cochrane.de/cochrane/revabstr/ab003008.htm
http://www.backspecialist.co.uk/Main/causes.htm
labor pain:
http://216.239.39.104/search?q=cache:-3x5-ga3pA0J:www.babycaretens.com/+tens+pain&hl=en&ie=UTF-8
pelvic pain:
http://www.icsoffice.org/publications/1999/read/pelvic%20floor/323.htm
arthritis pain:
http://216.239.39.104/search?q=cache:iYKt5SdWsrAJ:www.bodyclock.net/conditions/arthritis-right.html+tens+pain+arthritis&hl=en&ie=UTF-8
A brief discussion of TENS and types of pain treated with TENS:
http://www.apexmedical.com.tw/what's%20TENS.htm
A TENS unit works by applying light 'shocks' to the skin which
penetrate to the nerves underneath (this is the 'trans-epidermal'
portion of the name). All sensory nerves (pain, touch, etc...) head
to the spinal cord from the periphery. In the spinal cord, the nerves
take different pathways to the brain depending on what it is that they
sense. Different nerves send information to the brain about hot,
cold, pain, light touch, vibratory touch, position sense, and stretch
and these nerves take different pathways to reach the brain. For this
discussion, we really only need to address two of these pathways,
those of light touch and those of pain. The nerves which conduct
light touch send signals to nerves in the spinal cord near where they
enter the cord. These second nerves send signals up towards the brain
as well as to other surrounding nerves. The signals sent to the brain
tell the brain that something has been touched. The signals to the
surrounding nerves serve to increase the signal-to-noise ratio by
inhibiting the action of these nerves - this is like a teacher telling
the class to be quiet so that their voice can be heard. Well, the
pain neurons send their signals to nerves in the spinal cord, and
these nerves also ascend towards the brain. However, the pain nerves
are slower at sending their signals to the spine than are the light
touch nerves, so the first nerves that get to silence their neighbors
are the light touch nerves; and the nerves getting silenced are the
pain nerves. This method of analgesia is referred to as 'gating'.
Additionally, once the sensory fibers of the pain neurons reach the
brain, an area of the brain that helps to control pain is activated
and endorphins are released - endorphins help to decrease the
perception of pain (sometimes called 'natural opioids').
A nice, brief overview of the mechanism:
http://www.electrotherapy.org/electro/tens/tens.htm
A brief overview of the TENS mechanism:
http://www.medcareservice.com/Story.cfm?StoryID=6
Another common example of this that everyone has seen is the tendency
to grab at and hold an injured hand - this serves to reduce the pain
perceived in the hand by the same mechanism.
http://psy.ucsd.edu/~mgorman/lecture12.html
Acupuncture likely produces similar effects, although this is still
under study.
http://users.med.auth.gr/~karanik/english/articles/phantom.html
Please feel free to ask for clarification of any of the material which
I have posted.
synarchy
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