Fibromyalgia (FMS) is a disease characterized by widespread chronic pain, fatigue, memory loss, and many other common symptoms. It affects approximately 10 million Americans – of which 75-90% are women – and is a significant burden to deal with for all.
It’s frustrating how little we actually know about this disease. That said, science is beginning to uncover more and more about FMS and its effects on the entire body and, more specifically, the central nervous system and brain.
To understand how fibromyalgia causes the symptoms it does, we have to understand how pain is transmitted in the body. Generally, speaking, painful stimuli are carried to the spinal cord by two types of nerve fibers – C-Fibers and A-delta Fibers.
C-fibers are typically very sensitive and tend to carry dull and burning sensations of pain, while A-delta fibers are usually only sensitive to the strongest of painful stimuli. Signals are carried by these fibers to the spinal cord, where they are translated into chemical signals that are carried up the spinal cord to the brain.
The most striking effect of FMS is chronic pain and hypersensitivity to painful stimuli. But what causes the intense pain experienced in FMS? The simple answer is that for those suffering from fibromyalgia, the body’s normal pain pathway is disrupted. Over activation of C-fibers, as associated with FMS, leads to increased sensitivity to pain.
Since C-fibers are overwhelmed with painful input, A-delta fibers, which are typically only activated by strong stimuli, begin carrying some of the signals usually conveyed by C-fibers. As a result of this process, even the most delicate touch can be misinterpreted by the body as pain.
Certain neurochemicals are likely to cause this hypersensitivity. Generally speaking, FMS affects two main neurochemicals – Substance P and Serotonin. Substance P, named for pain, is produced in the body as a result of painful stimuli. It works by altering neurons in the spinal cord to create a sensation of pain; it also diffuses up and down the spinal cord, which is one of the main reasons that pain seems to pervade the body in FMS.
High levels of substance P lead to activation of NMDA receptors in spinal cord neurons – which are usually inactive during acute pain – that send signals directly to the brain. Serotonin, on the other hand, usually inhibits the activity of substance P in the brain. However, in the FMS brain, levels of serotonin are abnormally low, which not only prevents the body from dealing with the pain but it also leads to the production of more substance P in the brain and facilitates descending pain signals.
Though the activity and levels of Substance P and Serotonin in the body are likely the main culprits in the chronic pain associated with FMS, there are other factors that can make someone more sensitive to pain. One such factor is the decreased effectiveness of the endorphins and opiates made within the body. Despite the fact that levels of these chemicals are relatively normal in FMS, these natural painkillers require serotonin to work. And, because serotonin levels are low in FMS, the body has less ability to fight pain from within.
Another important factor contributing to FMS associated pain is increased levels of nitric oxide in the spinal fluid that occurs with low serotonin. Nitric oxide increases pain in the muscles by starving muscles cells of energy (in the form of Adenosine Triphosphate) and causing muscle cell death.
In sum, FMS is a disease that affects the body’s ability to interpret and deal with painful stimuli. Currently, the main treatments for FMS aim to increase levels of serotonin within the body, which is one of the main reasons doctors often prescribe antidepressants as treatment.
Yet, with more being uncovered about this relatively new disease, there may be a more effective treatment on the horizon. Drugs and procedures that target substance P, serotonin, nitric oxide, and other neurochemicals are likely to the focus of doctors and researchers in the near future.
For further information:
-National Fibromyalgia Association (NFA) – www.fmaware.org
-Fibromyalgia Symptoms – www.fibromyalgia-symptoms.org
-Wallace, Daniel J.; Wallace, Janice Brock. All about Fibromyalgia: A Guide for Patients and Their Families.
Cary, NC, USA: Oxford University Press, Incorporated, 2002.