Differential diagnosis of vasovagal syncope: Fibromyalgia

Fibromyalgia (FM) syndrome is a complex and challenging condition for healthcare systems worldwide. A chronic disease of unknown etiology, it is characterized by widespread pain and symptoms that may include fatigue, sleep disturbances, bowel and bladder disorders, mood disorders, neurocognitive impairment, presyncope, and syncope. It can develop at any age, and is similarly prevalent in different countries, cultures, and ethnic groups with a significant predominance of women. The recorded population prevalence rates range from 2 to 8%, depending on the diagnostic criteria used. Emerging evidence indicates that increased pain processing within the central nervous system plays a primary pathophysiological role. Recent studies have identified distinct FM subgroups on the basis of their clinical, neurochemical, and neuroendocrinological abnormalities, including increased cerebrospinal fluid levels of substance P and excitatory amino acids, and functional anomalies in the hypothalamic—pituitary—adrenal (HPA) axis and the sympathoadrenal (autonomic nervous) system.