Hyperalgesia

Hyperalgesia is an abnormal increase in sensitivity or an amplification of normally painful or uncomfortable stimulus. A person with hyperalgesia experiences an excessive amount of pain compared to the physical severity of damage or illness in their body.

Generalized hyperalgesia is common in fibromyalgia (FMS) and chronic fatigue syndrome (ME/CFS) and some studies indicate it may be partly caused by a mechanism in which microglial accumulation and activation is involved, as well as other possible immune system changes, such as complement system product C4a.

Symptom recognition

Hypersensitivity to pain is a sensory symptom recognized in the Canadian Consensus Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, and hyperalgesia is one of the examples of significant pain included in the International Consensus Criteria for Myalgic Encephalomyelitis.

Notable studies

• 2010, Evidence for generalized hyperalgesia in chronic fatigue syndrome: a case control study
• 2014, A chronic fatigue syndrome model demonstrates mechanical allodynia and muscular hyperalgesia via spinal microglial activation
• 2019, Exercise-induce hyperalgesia, complement system and elastase activation in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome - a secondary analysis of experimental comparative studies

See also

• Allodynia
• Fibromyalgia
• Pain
• Pain relief (analgesics)

Learn more

• Hyperalgesia: Causes, Symptoms, Treatment, and More - WebMD
• Allodynia and Hyperalgesia in Neuropathic Pain Fact Sheet - International Association for the Study of Pain

myalgic encephalomyelitis (M.E.) - A disease often marked by neurological symptoms, but fatigue is sometimes a symptom as well. Some diagnostic criteria distinguish it from chronic fatigue syndrome, while other diagnostic criteria consider it to be a synonym for chronic fatigue syndrome. A defining characteristic of ME is post-exertional malaise (PEM), or post-exertional neuroimmune exhaustion (PENE), which is a notable exacerbation of symptoms brought on by small exertions. PEM can last for days or weeks. Symptoms can include cognitive impairments, muscle pain (myalgia), trouble remaining upright (orthostatic intolerance), sleep abnormalities, and gastro-intestinal impairments, among others. An estimated 25% of those suffering from ME are housebound or bedbound. The World Health Organization (WHO) classifies ME as a neurological disease.

microglia A type of immune cell, called a macrophage, that lives in the brain. For historical reasons, macrophages have different names based on the part of the body that they normally live in. Macrophages that normally live in the blood are called monocytes. Macrophages that normally live in the skin are called Langerhans cells. Macrophages that normally live in the liver are called Kupffer cells. And macrophages that normally live in the central nervous system are called microglia. Microglia were originally classified as glial cells, under the assumption that the cells had a merely structural function, before it was realized that the cells were in fact immune cells. As the "sentinel cells" of the central nervous system, microglia survey their environment for abnormalities such as infection or tissue damage, and then initiate an immune response to fight the infection or repair the tissue damage.

physiological Concerning living organisms, such as cells or the human body.  Physio logical (as in physio) is not to be confused with psych ological (emotional stress).