Doctors have identified an entirely unique and separate sensory system located throughout our blood vessels and sweat glands which they believe could explain conditions like fibromyalgia. Writing in the journal Pain, the researchers say the human sensory experience is far more complex and nuanced than previously thought.
"It's almost like hearing the subtle sound of a single instrument in the midst of a symphony," said the study's senior author Frank Rice. "It is only when we shift focus away from the nerve endings associated with normal skin sensation that we can appreciate the sensation hidden in the background."
The researchers discovered this hidden sensory system by studying two unique patients who were diagnosed with a previously unknown abnormality. These patients had an extremely rare condition called congenital insensitivity to pain, meaning that they were born with very little ability to feel pain.
"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 researcher David 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."
Analyzing skin biopsies, the researchers found that the samples lacked all the nerve endings normally associated with skin sensation. Incredibly, it appeared to be the presence of sensory nerve endings on the small blood vessels and sweat glands embedded in the skin that allowed the patients to "feel."
"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," explained Rice.
"What we learned from these unusual individuals is that there's another level of sensory feedback that can give us conscious tactile information. Problems with these nerve endings may contribute to pain conditions such as migraine headaches and fibromyalgia, the sources of which are still unknown," he said in conclusion.
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Source: Albany Medical College