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Fibromyalgia syndrome: a pain modulation disorder related to altered limbic function?JAY A. GOLDSTEIN As a physician who specializes in the diagnosis and treatment of chronic fatigue syndrome (CFS) and fibromyalgia syndrome (FMS), I see a large number of patients who also have such problems as irritable bowel syndrome, panic disorder, amnestic disorder, allergic rhinitis, blurred vision, muscle fasciculations, myasthenia, interstitial cystitis, sleep disorders, headache, bruxism, irritable bladder, alopecia, thermoregulatory dysfunction, lymphadenalgia, dyspnoea, chemical sensitivity, endometriosis, late luteal phase dysphoric disorder, heart palpitations, photophobia, vertigo, Raynaud phenomenon and dysmenorrhoea. Some patients have immune activation related to 'overlap syndromes' with such disorders as systemic lupus erythematosus and multiple sclerosis. Over half report feeling well until they had 'the worst flu of my life', after which they never felt the same, so that investigation of persistent viral infection or 'hit and run' viral episodes that result in long-term functional impairment of affected and bystander cells is relevant.It is quite common for me to consult with individuals who have many of the above disorders. Initially, most of them seemed unrelated. Looking for a mechanism to produce such a wide range of illnesses led me to the study of neuroimmunoendocrine networks, especially the limbic system and its projections. This myriad of signs and symptoms may be explained by limbic dysfunction.The literature discussing the structure and function of the limbic system and its cortical projections (Figure 1), an example of a neural network which uses a parallel distributed computational strategy, is complex and may be unfamiliar to many readers of this volume. These topics have been well discussed by M. -Marsel Mesulam (1985, and these works form a good foundation for the understanding of limbic physiology and its derangements.One can view the limbic neural network functioning as a computer, processing intero-and exteroceptive stimuli (input), primarily via a bewildering array of chemically transduced messages, integrating them with experiences and attitudes (processing), and selecting responses (output) that should ideally maximize the survival capabilities of the individual (Figure 2).