Do neuroinflammation and pro-inflammatory cytokines drive central sensitization and chronic widespread pain in fibromyalgia?

Fibromyalgia is characterized by nociplastic pain, where the central nervous system amplifies sensory signals rather than accurately reflecting peripheral tissue damage. Current research suggests this state is driven by a complex interplay between the immune system and the brain, particularly through the activation of non-neuronal cells.

Clinical and effectiveness evidence

• Central sensitization is a hallmark of fibromyalgia, with approximately 69% of patients demonstrating extreme scores on the Central Sensitization Inventory (CSI).
• Higher levels of central sensitization are directly correlated with increased pain intensity and functional impairment.
• Quantitative Sensory Testing (QST) consistently shows that individuals with fibromyalgia have lower thresholds for mechanical and thermal stimuli compared to healthy controls, indicating a systemic state of pain hypersensitivity.
• Clinical studies using the Widespread Pain Index (WPI) demonstrate that chronic widespread pain is the primary phenotypic expression of this underlying central hyperexcitability.

Mechanistic explanations

• Neuroinflammation is primarily driven by the activation of microglia and astrocytes in the central nervous system. This activation is often mediated via Toll-like receptor 4 (TLR4).
• Activated glia release pro-inflammatory cytokines, specifically TNF-alpha, IL-1beta, and IL-6. These molecules induce a state of "sickness behavior" and enhance pain signaling.
• These cytokines act on neurons to increase the phosphorylation of NMDA and AMPA receptors, enhancing excitatory glutamatergic transmission.
• Simultaneously, these inflammatory mediators impair inhibitory GABAergic and glycinergic signaling. This dual action—increasing excitation while decreasing inhibition—promotes maladaptive long-term potentiation (LTP) in the spinal dorsal horn, maintaining the state of central sensitization.

Bottom line

Neuroinflammation and cytokine signaling are fundamental drivers of central sensitization, which serves as the physiological basis for chronic widespread pain in fibromyalgia. This mechanistic chain is supported by high-confidence evidence linking glial activation to the synaptic changes that cause pain amplification.