The pain of fibromyalgia can be agonizing, life-changing, and above all, confusing. After all, there’s so much we don’t know about pain, particularly the pain of fibromyalgia. And what we do know can be so complicated that’s it’s difficult to keep it straight.
For instance, did you know that there are actually different kinds of pain?
And finding a place to put fibromyalgia in those categories is difficult. Until 2011, it was classified as neuropathic pain. That year, doctors decided that this wasn’t a good fit and reclassified it as idiopathic, or the “we don’t have any idea what causes this pain” category. However, there was a reason that fibromyalgia was once considered neuropathic. And there are many reasons to think that fibromyalgia still belongs in the neuropathic category.
More importantly, understanding how neuropathic pain works can still teach us a lot about fibromyalgia itself and possibly how it might be cured.
So, what is neuropathic pain? And what can it tell us about fibromyalgia?
What Is Neuropathic Pain?
Pain is grouped into three larger categories: nociceptive, neuropathic, and idiopathic. Nociceptive pain is caused by things that trigger receptors in the skin called nociceptors. Anything like a cut, burn, or even something like arthritis can send a stimulus to these receptors. They then send an electrical signal along the nerves to the brain, which the brain then interprets as pain.
Neuropathic pain is a little bit different. Rather than being caused by a physical condition like an injury, neuropathic pain comes from the nerves themselves. Usually, it occurs after damage to the nervous system. And there are many conditions that can cause neuropathic pain like chronic alcoholism, multiple sclerosis, or chemotherapy. Really, any condition that can lead to nerve damage results in neuropathic pain.
The sensation is usually described as “electrical,” like you’re being shocked. But the pain can also be sharper and stabbing or produce a tingling sensation. And it can sometimes be hard to tell neuropathic pain from physical pain in the muscles, especially with a condition like fibromyalgia.
Because fibromyalgia seems to involve activity in the nerves and doesn’t arise from a physical source, it used to be considered neuropathic pain. But in 2005, it was moved into the idiopathic category. Idiopathic pain is a confusing category. And really, it’s just a way for doctors to classify pain when they have no idea what causes it.
The primary reason that fibromyalgia was moved out of the neuropathic category is because people with fibromyalgia usually don’t show signs of nerve damage. But as with all things regarding fibromyalgia, that’s complicated. And it turns out that many people with fibromyalgia do experience nerve damage.
Neuropathic Pain And Fibromyalgia
In fact, in around half of the patients with fibromyalgia, doctors can find evidence of some damage to the nerves. But that also means that half of all people who suffer from the condition don’t have nerve damage. So, why do they still experience pain in their nerves?
Unfortunately, we don’t really know the answer to that question. Some have suggested that over time, the nervous system can become hyper-sensitized to pain. It then sends pain signals to the brain without any actual damage to the nerves themselves.
This may be what is happening with fibromyalgia. We know that people often develop fibromyalgia after trauma, both mental and physical. There’s evidence that both cases can lead to nervous system over-sensitivity.
Another possibility is that fibromyalgia is caused by immune cells that affect the nervous system called “microglia“. These cells play an important role in neuropathic pain. They can pass through the barrier between the blood and the brain and help heal damaged nerve endings.
But sometimes, these cells become hyper-sensitive. They begin to pick up on signals of nerve damage that isn’t there and release something called cytokines. These cytokines cause inflammation in the nerves, which sends back more pain signals, which triggers the microglia to release more cytokines.
As you can imagine, that process forms an endless loop of pain and can even damage the nerves over time, which could potentially lead to hypersensitivity.
One of the most compelling pieces of evidence for this theory is that people with fibromyalgia have elevated levelsof something called leptin in the blood. In fact, researchers have even found that they can predict how severe a patients pain will be by measuring the levels of leptin.
And leptin also passes through the barrier between the blood and the brain and triggers the release of microglia. That cycle of leptin, microglia, and nerve pain may actually be the cause of fibromyalgia.
Researchers hope that by one day understanding why people with fibromyalgia release more leptin, and how the cycle works, they may be able to find a cure for the condition.