Researchers Discover Hidden Sensory System in the Skin: Could It Shed Light on Some Pain Conditions?
Medical science has long known that our nerves make up the sensory system that gives us the ability to touch and feel. However, now researchers have learned that the human sensory experience is far more complex than previously thought. A groundbreaking new study published in the December 15 issue of the journal Pain reveals the discovery of a unique and separate sensory system located throughout the blood vessels and sweat glands.
The research team discovered this hidden sensory system by studying two unique patients who were diagnosed with a previously unknown abnormality by lead author David Bowsher, M.D., Honorary Senior Research Fellow at the University of Liverpool's Pain Research Institute. These patients had an extremely rare condition called congenital insensitivity to pain, meaning that they were born with very little ability to feel pain. Other rare individuals with this condition have excessively dry skin, often mutilate themselves accidentally and usually have severe mental handicaps. "Although they had a few accidents over their lifetimes, what made these two patients unique was that they led normal lives. Excessive sweating brought them to the clinic, where we discovered their severe lack of pain sensation," said Dr. Bowsher. "Curiously, our conventional tests with sensitive instruments revealed that all their skin sensation was severely impaired, including their response to different temperatures and mechanical contact. But, for all intents and purposes, they had adequate sensation for daily living and could tell what is warm and cold, what is touching them, and what is rough and smooth."
The mystery deepened when skin biopsies revealed that these patients lacked all the nerve endings normally associated with skin sensation – but they were still able to feel various stimuli. How was this possible?
Frank Rice, PhD, a Neuroscience Professor at Albany Medical College, whose laboratory analyzed the biopsies, said, "For many years, my colleagues and I have detected different types of nerve endings on tiny blood vessels and sweat glands, which we assumed were simply regulating blood flow and sweating. We didn't think they could contribute to conscious sensation. However, while all the other sensory endings were missing in this unusual skin, the blood vessels and sweat glands still had the normal types of nerve endings. Apparently, these unique individuals are able to 'feel things' through these remaining nerve endings."
Dr. Rice also speculated, “Problems with these nerve endings may contribute to mysterious pain conditions such as migraine headaches and fibromyalgia, the sources of which are still unknown, making them very difficult to treat."
A Personal Note
I find this discovery fascinating on a very personal level. As I've mentioned before, I am extremely sensitive to heat. I get too warm very easily and when I do, my skin turns red and anything that touches me is painful – even my clothes. I can't help but wonder if that increased pain and sensitivity could be coming from this sensory network in my blood vessels and sweat glands. I'm certainly looking forward to more research being done to learn all the possible implications of this discovery.
Source: Adapted from materials provided by Integrated Tissue Dynamics (INTIDYN), via EurekAlert!, a service of AAAS.
Journal Reference: Bowsher D, et al. Absence of pain with hyperhidrosis: A new syndrome where vascular afferents may mediate cutaneous sensation. PAIN. 2009 Dec 15;147(1-3):287-98.