Chronic pain/fibromyalgia… experts say nerves in the spinal cord could be to blame
A nerve mechanism in the spinal cord could be capable of sending accidental pain signals to the brain, says a new study published in Cell. By charting the spinal circuits that process and transmit pain signals in mice, the study may provide the groundwork for finding ways to treat pain disorders that have no clear physical cause.
“Until now, the spinal cord circuitry involved in processing pain has remained a black box,” explains Prof Martyn Goulding who is involved in the work. “Identifying the neurons that make up these circuits is the first step in understanding how chronic pain stems from dysfunctional neural processing.”
Some people who have chronic pain are sensitive to things that don’t normally cause pain, such as a light touch to the hand or a slight change in skin temperature. These conditions include fibromyalgia and nerve damage that is caused by diseases such as autoimmune disorders.
“These disorders are extremely frustrating for patients, because there is still no effective treatment for such chronic pain disorders,” says Prof Qiufu Ma, co-senior author.
The new findings begin to explain how a light touch can cause discomfort in someone with chronic pain; if something is awry in the pain circuitry, the sensations of touch that normally travel through specific mechanoreceptors could instead activate other nerves that trigger a pain signal. And mechanoreceptor fibres that project to the spinal cord from a missing limb might spur accidental pain signals.
“Normally, only pain receptors are involved in sending pain signals to the brain, but when the spinal dynorphin inhibitory neurons are lost, touch sensation are now perceived as painful,” Prof Goulding says. “This really opens the door to understanding what’s happening in these pain disorders where the cause of the pain is seemingly innocuous or not known. It could be that something has gone awry in how this spinal circuitry is operating, so sensations become jumbled together and emerge as pain.”
Image credit: Nick Webb
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