Complex Regional Pain Syndrome Evolving to Full-Blown Fibromyalgia: A Proposal of Common Mechanisms.

ABSTRACT

BACKGROUND: Spread of complex regional pain syndrome (CRPS) outside the affected limb is a well-recognized phenomenon; nevertheless, the actual evolution from CRPS to fibromyalgia is poorly documented. Similar mechanisms have been recently put forward to explain the development of CRPS and fibromyalgia including dorsal root ganglia (DRG) hyperexcitability and small fiber neuropathy. OBJECTIVES: The aims of this study were to describe 3 cases with typical CRPS evolving to full-blown fibromyalgia and to discuss the potential pathogenetic mechanisms linking these debilitating illnesses. METHODS: This was a review of medical records and PubMed search on the relationship between CRPS-fibromyalgia with DRG and small nerve fiber neuropathy. RESULTS: Our 3 cases displayed over time orderly evolution from CRPS to fibromyalgia. Dorsal root ganglion hyperexcitability and small fiber neuropathy have been recently demonstrated in CRPS and in fibromyalgia. Dorsal root ganglia contain the small nerve fiber cell bodies surrounded by glial cells. After trauma, DRG perineuronal glial cells produce diverse proinflammatory mediators. Macrophages, lymphocytes, and satellite glial cells may drive the immune response to more rostrally and caudally located DRG and other spinal cord sites. Dorsal root ganglion metabolic changes may lead to small nerve fiber degeneration. This mechanism may explain the development of widespread pain and autonomic dysfunction. CONCLUSIONS: Clinicians should be aware that CRPS can evolve to full-blown fibromyalgia. Spreading of neuroinflammation through DRG glial cell activation could theoretically explain the transformation from regional to generalized complex pain syndrome.