We know that fibromyalgia is a central nervous system disorder; the question is whether we can do away with the “central” part and call it simply a nervous system disorder.
It’s clear that somewhere around 40% of people with FM also have small nerve fiber damage (SFN).
That neuropathy describes not only the disappearance of some of the small nerves in the skin and eyes but the thinning of the remaining ones in the skin.
That last finding is so unusual that it’s been suggested that the small nerve fiber problems found in FM be called something else entirely ( small nerve pathology)
A major question facing SFN researchers in fibromyalgia is how important the small nerve fiber problems are to fibromyalgia.
Daniel Clauw, a prominent FM researcher, believes the SFN is probably incidental and has little to do with the core pathology of the disease. Others believe that the process causing the loss and thinning of the unmyelinated fibers in FM probably plays a core role in the disease.
This Spanish study examined nerve thickness in a new part of the body – the retina of the eye.
Until now nerve studies have focused on the peripheral nerves found in the body. Because this part of the eye is considered to be part of the central nervous system, this study was the first to examined potential small nerve problems in that area.
The study found that even patients with “mild” FM displayed “subclinical” thinning of the retinal nerves in the nasal and temporal sectors of the eye.
The degree of thinning was not significantly greater in people with longer duration or more severe FM, but was greater in the “biologic FM” subset; i.e., people with FM who did not display anxiety or mood disorders, than in FM patients with mood disorders
Natelson has found a similarly curiously pattern in ME/CFS: ME/CFS patients without mood disorders display more neurological abnormalities than those with mood disorders.
Noting that the retinal and optic nerves in the eye derive from brain tissue during development, and thus are considered part of the central nervous system, the authors suggested that their findings suggested that the eyes of FM patients could function as windows into whatever central nervous system problems present.
The unmyelinated nerves in the temporal quadrant of the eye – the most effected section of the eye in FM – are amongst the first nerves to show damage in neurodegenerative diseases.
The study findings buttressed the idea that FM is a neurodegenerative; i.e. a nerve damaging disease – placing it in the same general category as Alzheimer’s, Parkinson’s, multiple sclerosis and others. The author asserted the findings indicate that FM is a neurological disease which produces “neuropsychological” symptoms.
The idea that FM is a neurodegenerative disease is not a new one. Something after all has to be causing the nerves in the pain inhibiting pathways of the central nervous system to more or less give up the ghost, and plenty of evidence suggests that nerve damage is present in the skin and corneas of significant numbers of people with FM. This may be the first study, though, to present physical evidence that FM is neurodegenerative in the same way
Subclinical Losses Mean No Loss of Eyesight
There was no sense in this study that the nerve loss was damaging FM patients; the amount of the fiber loss was subclinical; i.e., not enough to produce symptoms.
The authors suggested that because OCT scans are quick, cheap and non-invasive that they could easily become part of the diagnostic criteria for the disease.
Given the high degree of FM misdiagnosis reported, being able to differentiate fibromyalgia from other pain states which are not “neurodegenerative” would be a major step forward.
The tie that binds in all these FM studies are problems with the small unmyelinated nerves .
Because peripheral neuropathies found in diseases like Guillian-Barre Syndrome do not affect the corneal nerves the authors asserted that the thinning they found in FM had a central nervous system sensitization.
Corneal thinning in diabetes, however – a disease which is not associated with central nervous sensitization – indicates that corneal thinning can occur in other ways.
This last sentence almost negates the whole point of the study but gives rise to other interesting questions.
FM is such a “strange” disease, that we cannot expect normal functioning, but deciding what meaning these abnormalities have is even more difficult than finding them in the first place.