Fibromyalgia

What it is. "Fibromyalgia is a chronic pain disorder characterized by widespread musculoskeletal pain, often accompanied by fatigue, cognitive dysfunction, a variety of somatic complaints, and psychiatric disturbances such as depression and anxiety." "Fibromyalgia is considered a disorder of pain regulation and is classified as a condition of central sensitization."

How it works. "Patients with central sensitization experience hypersensitivity to pain due to amplified neural signaling in the CNS. They perceive noxious stimuli as painful at lower levels of physical stimulation compared to healthy controls." "Rapidly repetitive, short, noxious stimuli cause higher-than-normal increases in pain intensity, partly due to a deficiency in endogenous analgesic systems. This phenomenon is referred to as the temporal summation of pain."

The evidence. "Brain imaging studies that show an amplified pain response to experimental pain stimuli, along with changes in neurotransmitter structure and function and modifications in resting-state functional connectivity, provide strong evidence that these CNS alterations are key contributors to the condition's hallmark features." It is not an inflammatory disease: anti-inflammatory drugs "are usually not effective because fibromyalgia does not cause tissue inflammation" (NIAMS).

Triggers and risk. "Experts have not identified a single cause of fibromyalgia. Instead, experts believe that a combination of multiple physical and emotional stressors can trigger or worsen symptoms." "Some identified causes include infections such as Lyme disease and physical or emotional trauma." "Fibromyalgia tends to run in families," and "The risk of developing fibromyalgia is higher in individuals with an existing rheumatic disease."

Sleep and pain. "Some studies suggest that sleep disturbances may precede the onset of pain." "For example, disrupted sleep can increase pain, and pain can further disturb sleep." Patients "often report light sleep, frequent early morning awakenings, difficulty falling back asleep, and not feeling well-rested in the morning."

Stress systems (a hypothesis). "Many experts believe that dysfunction of the autonomic nervous system, characterized by reduced heart rate variability (HRV) and changes in skin conductance, combined with an overactive stress response and dysregulation of the HPA axis, contributes to the relationship between pain, sleep disturbances, and mood and cognitive symptoms." Central and peripheral pain "can intensify each other, meaning a knee injury may exacerbate fibromyalgia symptoms and vice versa."

[ACR] The history (StatPearls, describing the ACR criteria). "The initial diagnostic criteria, established in 1990, focused on a specific number of tender points. However, standardizing the examination proved difficult, leading to limited use among physicians." The ACR updated the criteria in 2010, and "In 2016, the ACR modified the criteria to include a generalized pain criterion, requiring pain in 4 out of 5 regions to reduce misclassification of regional pain syndromes."

Today. "The WPI measures the number of painful body parts from a list of 19, while the SS score estimates the severity of fatigue, cognitive dysfunction, and psychiatric and somatic symptoms." The 2016 cutoffs are "WPI score of 7 or more with an SS score of 5 or more or a WPI score of 4 to 6 with an SS score of 9 or more," and "Symptoms should be present at a similar level for at least 3 months." Current guidelines "no longer recommend palpating specific soft tissue sites or documenting a specific number of tender points."

A clinical diagnosis; tests exclude look-alikes. "Routine laboratory and imaging tests are typically normal and, while not required for diagnosis, are essential for excluding other potential underlying conditions" such as "inflammatory arthritis, osteoarthritis, thyroid disease, and localized pain syndromes." "Accurate identification of fibromyalgia is crucial to preventing unnecessary testing, implementing evidence-based treatment, and validating the patient’s" experience.