Two Types of Fibromyalgia
Researchers working on the puzzle of fibromyalgia syndrome (FMS) are adding more and more pieces. While we don't yet have a complete picture, we're getting closer. Many experts believe the condition is brought on by complex, abnormal responses to stress and could be linked to a genetic predisposition. Studies show, with FMS, the parts of your brain and central nervous system that deal with pain signals work differently from other people's. This is called central sensitization.
Experts are learning a lot about what leads to FMS, but they're still not clear on why these things lead to FMS in some and not in others.
Fibromyalgia is grouped into two categories -- primary and secondary. Primary FMS is the most common and is also called "idopathic" FMS, meaning it has an unknown cause. Secondary FMS is associated with other conditions.
Secondary Fibromyalgia
Secondary fibromyalgia appears either after or in conjunction with other medical problems, usually one of the following:
- Physical injury, especially to the neck
- Ankylosing spondylitis (arthritis that affects the spine)
- Surgery
- Lyme disease (May trigger FMS even after Lyme has been treated)
- Hepatitis C (some studies hint at this association)
- Endometriosis
When there's another condition at work, it can give doctors a real a challenge when it comes to diagnosing secondary FMS. First, it can be difficult to sort out what condition is causing what symptoms. Second, FMS is considered a diagnosis of exclusion because anything reversible has to be treated before a doctor can diagnose it.
Primary (Idiopathic) Fibromyalgia
Suspected causes of primary FMS include chronic sleep disturbance, abnormalities in brain chemicals and hormones, psychological and social effects, and muscle abnormalities. Some researchers are looking at nitric oxide levels.
Chronic sleep disturbance
Sleep disturbances and fibromyalgia go hand and hand, and some experts believe sleep disturbances come first. People with FMS have higher than average rates of restless leg syndrome, periodic limb movement disorder (PLMD) and sleep-related breathing disorders.
In one study, people with FMS had faster rates of cyclic alternating sleep pattern (CAP), which leads to a non-refreshing sleep. Researchers concluded the increased rate leads to serious sleep problems that made FMS symptoms worse.
Some sleep problems of FMS may be linked to levels of the nervous-system chemicals serotonin and melatonin, which help regulate sleep-and-waking cycles. (Keep reading for more information on these chemicals.)
Brain chemical & hormonal abnormalities
Researchers know people with fibromyalgia can have numerous abnormalities in their hormonal, metabolic and brain-chemical activity, but they're not sure whether these are causes of fibromyalgia or the effect of pain and stress on the central nervous system. People with FMS may have imbalances in any of the following brain chemicals:
- Serotonin: low levels
Serotonin impacts your sleep cycle, pain level and feelings of well being. Low levels are linked to depression, migraine and irritable bowel syndrome, all of which frequently occur in people with FMS. - Melatonin: low levels
Your body makes melatonin from serotonin. Typically, serotonin levels increase in the morning to help you wake up, then drop at night as your body converts it into melatonin, which helps you sleep. Some studies show taking melatonin supplements can cut pain levels, improve sleep and improve depression symptoms in people with FMS. However, other studies have shown little or no improvement. - Stress hormones: low levels
Deficiencies in the stress hormones cortisol and norepinephrine make your body less able to cope with psychological or physical stress. (Physical stress includes infection or strenuous activity.) - IGF-1 growth hormone: low levels
This hormone promotes bone and muscle growth. Low levels are related to problems with thinking, low energy, muscle weakness an intolerance to cold. This level may be a marker of FMS rather than a cause. - Substance P: high levels
Substance P is a chemical messenger in the nervous system associated with pain perception. If you have too much, your brain gets too many pain signals. People with FMS can have up to three times the normal amount in their spinal fluid. - Abnormal pain perception: high activity levels
Some studies and brain scans suggest fibromyalgia patients have too much activity in the part of the brain and central nervous system that process pain.
Researchers are working to understand what these abnormalities mean and how this knowledge can lead to treatments.
Psychological & social effecs
According to studies, people with FMS are more likely than others to have experienced severe emotional and physical abuse. This suggests that post-traumatic stress disorder (PTSD) or chronic stress could play a strong role in the development of FMS in some people. Evidence shows that PTSD actually leads to changes in the brain, possibly from long-term over-exposure to stress hormones.
Muscle abnormalities
Though these things cannot be tested at your doctor's office or clinic, some research has shown that people with FMS have three kinds of muscle abnormalities:
- Biochemical
Some FMS patients have low levels of muscle-cell chemicals that make sure you have enough calcium in your muscles. When levels are low, the muscles stay contracted rather than relaxing. - Structural & blood flow
Researchers have found people with FMS have especially thick capillaries (tiny blood vessels). This could mean your muscles don't get enough oxygen-rich blood or other compounds you need for proper muscle function. - Functional
Experts don't know why this is but speculate that the pain and stress of the disease itself may harm muscle function.
Sources:
2007 About, Inc., a part of the New York Times Company. All rights reserved. "Fibromyalgia"
2007 ProHealth, Inc. All rights reserved. "Melatonin Deficiencies in Women"
1995-2007 Life Extension Foundation. All rights reserved. "Fibromyalgia"
