Fibromyalgia, chronic fatigue syndrome and many other related conditions are being classified as central sensitivity syndromes (CSS). Central sensitivity syndromes are illnesses that involve the central nervous system (spinal cord and brain). CSS illnesses have several similar features in common such as pain, fatigue, poor sleep, and sensitivity to painful and non-painful stimuli. Many people with Central Sensitivity Syndromes also have the presence of psychosocial (psychological and social) difficulties.
The concept of central sensitivity syndromes was formed by Dr. Muhammad Yunus, a rheumatologist from the University of Illinois. Twenty-five years ago, Dr Yunus and colleagues published the first controlled study of clinical characteristics of fibromyalgia and the first data-based criteria for diagnosis. In June of 2007, Dr. Yunus published an article interpreting the extensive body of research on fibromyalgia and his concept of central sensitivity syndromes.
Illnesses Considered Part Of The CSS Family
Fibromyalgia and other central sensitivity syndromes appear due to a complex interaction of genetic predisposition, enhanced pain perception, heightened physiologic distress combined with certain environmental factors.
There are 13 conditions that are related to central sensitization. These conditions include:
Chronic fatigue syndrome
Chronic pelvic pain
Certain forms of chronic headaches (tension and mixed)
Idiopathic low back pain
Interstitial cystitis (painful bladder syndrome)
Irritable bowel syndrome
Multiple chemical sensitivities
Myofascial pain syndrome
Primary dismenhorrhea (painful periods)
Restless leg syndrome
Temporomandibular joint disorder
The following mental health disorders overlap with CSS:
Generalized anxiety disorder
Post traumatic stress disorder
Features Of Fibromyalgia & Central Sensitivity Syndromes
In CSS, we become extremely sensitive to things that are processed by the central nervous system -bright lights, loud noises, strong smells and rough textures. It may also include certain foods and chemicals.
Some of the key features of Fibromyalgia and CSS include:
Disturbance in central pain processing – The pain of CSS comes from different abnormal pain types: Hyperalgesia and Allodynia.
Hyperalgesia is an increased sensitivity to pain. Normal pain from an injury is amplified and made worse. This seems to occur via immune cells interacting with the peripheral nervous system and releasing pain-producing chemicals (cytokines and chemokines).
Allodynia is pain from stimuli which do not normally cause pain such as a simple touch or from clothing rubbing against the skin.
Autonomic nervous system dysfunction – The autonomic nervous system regulates involuntary bodily functions such as breathing, heart rate, digestion and other processes.
Dysfunction of the HPA axis – The Hypothalamic-Pituitary-Adrenal Axis is part of the body’s stress response system. It regulates your temperature, digestion, immune system, mood and energy usage.
Abnormal levels of neurochemicals in the brain – Certain neurotransmitters (brain chemicals) are known to either increase or decrease pain transmission in the central nervous system. Neurotransmitters involved in fibromyalgia and CSS include: Serotonin, Norepinephrine, Dopamine, GABA and glutamate. You can read more about abnormal levels of neurotransmitters in fibromyalgia here.
There is mounting evidence that links fibromyalgia to other chronic pain disorders. Fibromyalgia and other central sensitivity syndromes have more in common than previously thought. This may explain why these conditions often overlap with each other. Dr Yunus believes that the term central sensitivity syndromes incorporates both biological and physiological components and will foster research in the appropriate areas and accelerate progress. It seems to have important significance for new directions for patient care and education.