Clinical meaning
Fibromyalgia is a central pain processing disorder characterized by widespread musculoskeletal pain, fatigue, and cognitive dysfunction. The pathophysiology involves central sensitization, where dorsal horn neurons in the spinal cord become hyperexcitable due to sustained nociceptive input, leading to amplified pain signal transmission to the brain. Elevated levels of excitatory neurotransmitters (substance P, glutamate) are found in cerebrospinal fluid, while inhibitory neurotransmitters (serotonin, norepinephrine, dopamine) are deficient. Functional MRI studies show augmented neural activation in pain-processing brain regions (anterior cingulate cortex, insular cortex, somatosensory cortex) in response to stimuli that would not normally be painful (allodynia). The hypothalamic-pituitary-adrenal (HPA) axis shows blunted cortisol response to stress, contributing to fatigue and pain amplification. Sleep architecture is disrupted with alpha-wave intrusion during delta (deep) sleep, preventing restorative sleep and perpetuating the pain-fatigue cycle. Glial cell activation in the CNS releases pro-inflammatory cytokines that further sensitize nociceptive pathways.