Fibromyalgia

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Fibromyalgia is a lifelong medical condition that is characterised by widespread pain, fatigue, waking unrefreshed and cognitive disorders. It is the prototypical centralised pain state where there is a fundamental problem with augmented pain or sensory processing and manifests in different parts of the body over time. While mental health complaints are common, the pain itself is not psychosomatic in nature.

Epidemiology

Fibromyalgia is present across the world, and has a prevalence ranging between 2% to 4%. It is the second most common rheumatological disorder after osteoarthritis. 10-15% of the population have chronic widespread pain, and there is no clear boundary separating those that have chronic widespread pain from those that have fibromyalgia.

The peak onset is 20-50 but it can occur at any age. and is about twice as common in women. In clinical practice it is predominantly diagnosed in women in late middle age. Other risk factors are increasing age, family history of chronic pain, obesity, and poor mental and/or physical health. It occurs in all countries and ethnicities.

Patients with fibromyalgia have roughly double the healthcare utilization compared to matched controls for at least a decade prior to diagnosis. Visits increase rapidly three years prior to diagnosis, then slightly decline after diagnosis, and rise again three years post-diagnosis, remaining at levels comparable to diagnosis but never reaching the level of two years prior to diagnosis. The overall benefit of the diagnostic process and medical input appears questionable at the population level.

Nearly all patients that are eventually diagnosed with fibromyalgia have a long history of having bouts of chronic regional pain various body regions over their lifetime dating back to adolescence. The most common reasons for clinical visits to GPs in order of frequency are depression, fatigue, chest pain, headache, sleep disturbance, dizziness, and IBS.

Risk Factors

There is often a strong familial predisposition to pain. Twin studies show that the risk of developing fibromyalgia is 50% genetic and 50% environmental. First degree relatives are more than 8 times as likely to also have fibromyalgia compared to controls. Many of the genes discovered thus far are involved in the regulation of neurotransmitters that modulate pain sensitivity, but genetic studies are not universally consistent and pain sensitivity is polygenic.

Psychological and other stressors are often a factor in the development and maintenance of the disorder, with the presence of sympathetic dysfunction, however it is not a psychosomatic condition. Environmental stressors are often identified, particularly those where there is acute pain that lasts a few weeks. For example motor vehicle accidents or certain infections.

Fibromyalgia is frequently observed as a comorbidity in other chronic pain conditions such as OA, RA, and lupus. About 15-30% of individuals with these rheumatic disorders meet FM criteria, and more individuals do not meet the criteria but display some FM elements, indicating the presence of pathophysiological abnormalities in CNS pain processing. The term "centralized pain" rather than "central sensitisation" is preferred when CNS factors play a significant role in magnifying pain and leading to other somatic symptoms.

Pathophysiology

The pain "set point" or "volume control" of an individual is determined partially by the levels of neurotransmitters on the left that amplify pain signals and those on the right that dampen pain signals. Therefore, an increase in neurotransmitters on the left or a decrease in those on the right may result in diffuse hyperalgesia, which is a common symptom of chronic pain conditions. The chart displays the levels of these neurotransmitters in the cerebrospinal fluid of fibromyalgia (FM) patients, with the arrows indicating the direction of abnormality. The opioidergic system is the "odd one out" being increased. Modified from Hochberg.

The current accepted hypothesis is that fibromyalgia is a centralised pain syndrome. This hypothesis describes fibromyalgia patients as having augmented pain, and augmented sensory processing in the brain.

There is increased pain to normally painful stimuli (diffuse hyperalgesia) and pain in response to normally non-painful stimuli (allodynia). Functional magnetic resonance imaging (fMRI) studies show that individuals with FM experience pain and similar brain activation patterns in brain areas involved in pain processing, even when given mild pressure or heat stimuli that most individuals would feel as "touch" rather than "pain".

Other imaging studies have shown that there is increased connectivity between brain regions involved in increasing pain transmission and decreased connectivity to key antinociceptive regions.

There is also an imbalance between excitatory and inhibitory neurotransmitters. There is an increase in glutamate and nerve growth factor that are facilitate nociception. The gabapentinoids likely work by reducing glutamatergic activity. There is also a decrease in neurotransmitters that inhibit pain or sensory processing like serotoinin, norepinephrine, and GABA. y-hydroxybutyrate and low doses of alcohol may work against low levels of inhibitory GABA. Furthermore the endogenous opioid system is increased, reducing mu-opioid receptor availability, and works paradoxically to increase pain. Low-dose naltrexone is thought to target this pathway.

The hypothalamic pituitary adrenal and autonomic nervous systems are frequently abnormal, but studies are inconsistent in the prevalence. Multiple psychosocial factors can influence these aspects of the body.

Around 40-50% of fibromyalgia patients have small fibre neuropathy (SFN). For example, Oaklander et al found that in 41 patients with unexplained widespread pain that started before the age of 21, 59% of children at definite SFN, 17% had probable SFN, and 22% had possible SFN. They then found that in a group of 27 fibromyalgia patients and 30 matched controls, 41% of fibromyalgia patients had definite SFN, compared to 3% in the control group. See Manuel et al for a summary.

Some central sensitisation framework proponents claim that the presence of small fibre neuropathy has unclear relevance, and may be a consequence not a cause of fibromyalgia, with peripheral nervous system changes in response to central nervous system sensitisation. This view is not universally shared. Manuel et al believe fibromyalgia to be related to a persistent hyper-adrenergic state, leading to dorsal root ganglia hyper-excitability, and neuropathic pain. They note the role of dorsal root ganglia sodium channel variants in the condition.

Clinical Features

The patient may report persistent pain for over three months, pain in more than one region, intrusive fatigue, impaired memory ("fibro fog"), sleep disturbance, and gastrointestinal disturbance. Other symptoms include increased pain sensitivity (e.g. pain with hugging), muscle stiffness, headaches, anxiety, depression, and irregular periods.

Pain is frequently accompanied by neurologic symptoms e.g. numbness or tingling.

A complete rheumatological, orthopaedic, and neurological examination should be performed.

Diagnosis

Fibromyalgia is over diagnosed. In one study in the US, the majority of individuals with a clinical diagnosis of fibromyalgia do not fulfil the diagnostic criteria.

2010 Criteria

Fibromyalgia Diagnostic Criteria ACR 2010 - 219 KB (f)

In 2010 the American College of Rheumatology (ACR) revamped the diagnostic criteria. There is no requirement for a tender point examination like in the ACR 1990 classification. Three criteria must be met for the diagnosis

1. Widespread Pain Index (WPI) ≥ 7/19 and Symptom Severity Scale (SSS) Score ≥ 5/12 or WPI between 3–6/19 and SSS ≥ 9/12
2. Symptoms being present at a similar level for at least 3 months
3. The patient does not have another disorder that would otherwise sufficiently explain the pain.

Conditions 1 and 2 are assessed by the Fibromyalgia Survey Questionnaire.

2016 Criteria

Fibromyalgia Diagnostic Criteria ACR 2016 - 328 KB (f)

The criteria were modified in 2016. A major change was that other conditions don't need to be ruled out and it can be diagnosed irrespective of other diagnoses.

Differential Diagnosis

The differential diagnosis must be viewed from two different perspectives. The first perspective is recognising that fibromyalgia type symptoms can occur as a co-morbidity alongside another condition. Fibromyalgia occurs alongside 15-30% of individuals with any autoimmune or chronic musculoskeletal pain condition when there is ongoing nociceptive input. This includes Rheumatoid Arthritis (12-20%), Spondyloarthritis (11-50%), lupus erythematosus (5-25%), Ehlers-Danlos syndrome, sickle cell disease, and cancer pain.

The second perspective is understanding that some conditions can mimic the symptoms and so the patient has a different diagnosis entirely, and fibromyalgia is not a comorbidity. Examples of this are Polymyalgia Rheumatica, hypothyroidism, and some neuromuscular conditions like statin-induced myopathy.

A problem occurs when considering another disease that has clinical features that can be similar to those with fibromyalgia. An obvious example is metastatic cancer.

Differential Diagnosis of Widespread Pain

• Autoimmune: Polymyalgia Rheumatica, Sjogren's Disease, Rheumatoid Arthritis, Connective tissue disease (autoimmune), Inflammatory myositis, Sarcoidosis, Celiac disease, Inflammatory Bowel Disease, Sarcoidosis
• Genetic: Heritable Connective Tissue Disorders, Neuromuscular Diseases (e.g. Myotonic Dystrophy type 2, Pompe Disease)
• Idiopathic: Fibromyalgia, Degenerative myopathies, Small Fibre Neuropathy
• Primary Joint disease: Osteoarthritis
• Neoplastic disease: Metastases, Multiple myeloma, Leukaemia, Lymphoma
• Infections: bacterial endocarditis, hepatitis B and C
• Bone disease: Osteomalacia, Osteomyelitis
• Endocrine: Hypothyroidism and hyperthyroidism, Hyperparathyroidism, Acromegaly, Diabetes, Vitamin D deficiency, endocrine myopathies
• Neurological: Parkinson disease, Neuropathies, Motor neurone disease, Chronic Inflammatory Demyelinating Polyneuropathy, Multiple sclerosis, Myalgias in rare disease (e.g., Stiff Person Syndrome), Myalgias with lesions of the central and peripheral nervous system
• Medication: opioids, statins, aromatase inhibitors, carbimazole, ezitimibe, metoprolol, minoxidil, PPIs, salbutamol, amiodarone, colchicine, ACE inhibitors

Investigations

First line screening tests to exclude somatic disease are FBC, CRP, CK, calcium, TSH.

Other tests to consider are ESR, LFTs, glucose, UEC.

Vitamin D levels are low in the majority of patients with chronic pain, but this test is not funded in NZ.

If there is suspicion of axial spondyloarthritis then consider HLA-B27, and RF if psoriatic.

If there is suspicion of Rheumatoid Arthritis then include anti-CCP, and RF.

ANA can be considered if there are consistent clinical features.

fMRI studies are very accurate at identifying fibromyalgia however it is not available in clinical practice.

Treatment

There is no highly effective treatment. Exercise is first line, medication is second line.

Education

When explaining the condition a useful analogy is an electric guitar. Pain processing is a lot like an electric guitar. To make an electric guitar louder you can either either strum the strings harder or turn up the amplifier. The strings in the guitar are equivalent to all the different nerves in different parts of the body.

All the information (pain, temperature, pressure, etc) comes up through the amplifier which is the spinal cord and the brain. If the amplifier is set high enough - through a combination of genetics and environmental stressors - then pain will occur. Everyone has their own amplifier setting on a range of 0-100. If you happen to have a setting of 70 that is higher than average, but less than fibromyalgia, you will feel more pain. While in fibromyalgia the amplifier is set to 95 or more.

The amplifier in fibromyalgia is not only set higher for pain processing, but for all sensory processing. For example there is increased sensitivity to sounds, lights, smells, and side effects from drugs. Fatigue, insomnia, and memory problems also often occur.

Exercise

Exercise is the first line treatment

Medication

Medication is second line. Opioid analgesics are generally not effective, possibly due to reduced mu-opioid receptor availability.

Resources

Fibromyalgia Diagnostic Criteria 2016 Article - Wolfe 2016.pdf - 618 KB (f)

Fibromyalgia - Members Subpage

See Also

• Small Fibre Neuropathy
• Central Sensitisation

History of the condition

See review by Hauser and colleagues.

Literature Review

Literature Review

Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf

Articles from all years: PubMed search, Google Scholar search.

TRIP Database: clinical publications about evidence-based medicine.

Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,