Fibromyalgia, the Optic Nerve, and Neurodegeneration

Are the eyes the window to whatever's going wrong with the brain in fibromyalgia? Research published in 2015 and 2016 suggests that it just might be.

Fibromyalgia is widely believed to be a condition of the central nervous system, which includes the brain and spinal cord. It also includes the light-sensing parts of our eyes and the structures that help our brains interpret what we see.

Chief among these structures is the optic nerve, which is similar to a cable made up of many small fibers. Among them is a layer of nerves called the retina nerve fiber layer (RNFL).

Those nerve fibers are of special interest to researchers because of other work that has uncovered dysfunction of the small nerve fibers. It suggests that, in people with fibromyalgia, small-fiber neuropathy (nerve damage) may be responsible for at least some of the pain.

In two studies, Spanish researchers have also discovered evidence of neuropathy in the small fibers of the eye.

Blood-Flow Problems

In the study published in 2015, researchers looked at blood flow to the optic nerve and the RNFL. Blood flow, also called perfusion, is hypothesized to be irregular in several regions of the brains of people with fibromyalgia.

Researchers examined and took photographs of the eyes of 118 people with this condition plus 76 healthy people in the control group.

The photos were then analyzed with special software. The researchers concluded that the fibromyalgia eyes did in fact show low abnormally low perfusion rates, including in a specific sector of the RNFL.

Optic Nerve Thinning

The study published in 2016 built on that research and involved many of the same researchers. This time, they included 116 people with fibromyalgia and 144 in the control group.

They found:

• A significant thinning of the RNFL in fibromyalgia compared to controls
• Greater RNFL thinning in those with severe fibromyalgia than in those with a milder case
• Greater RNFL thinning in subgroups without depression compared to those with depression

Neurodegeneration

Before this, fibromyalgia had been considered non-neurodegenerative, meaning that no biological structures were being damaged or destroyed as they're known to be in other neurological diseases such as multiple sclerosis or Alzheimer's disease.

However, this research suggests that fibromyalgia may, in fact, involve some neurodegeneration in structures inside the central nervous system.

This, combined with earlier research on small nerve fiber damage in the skin, could mean that the degeneration is not confined to the central nervous system but may extend to the peripheral nervous system, which includes the nerves in the limbs, hands, and feet.

The Relationship Between Fibromyalgia, the Optic Nerve, and Neurodegeneration

Fibromyalgia has always posed problems for doctors. There is pain, but no obvious cause. If this research is accurate, which won't be known until the study is replicated, it could mean that our pain comes from a very understandable source. After all, neuropathic pain has been recognized for a long time. Suddenly, it makes our "mysterious" pain not mysterious at all.

On the other hand, it opens new doors for questioning. If we have damaged nerves, then why? What is causing the damage?

Possible candidates could include autoimmunity, which would involve the immune system going haywire and attacking the nerves as if they were bacteria or viruses, and problems with how the body uses substances that grow or maintain nerves.

Researchers have long speculated about possible autoimmunity in fibromyalgia, but so far, we don't have solid evidence pointing toward it. Now that researchers have discovered actual damage, they may gain better insight into where to look for autoimmune activity. They may also be able to pinpoint shortages or inefficiencies in how nerves are maintained.

When it comes to diagnostic tests, it's too early to say whether abnormalities in the eye could lead to a more objective test than what currently exists. If so, it would be a major advancement in how fibromyalgia is detected.

Because the thinning was worse in cases that were more severe, it could provide a marker for doctors to monitor treatments as well as progression.

It's also possible that these discoveries could lead to targeted treatments.

We won't know the full impact of this research for some time, as any advancement in diagnostics and treatments would have to come after further research either confirms or contradicts these findings.