BERKELEY, CA (UroToday.com) - Idiopathic pain disorders (IPDs) consist of such conditions as temporomndibular joint disorders, fibromyalgia syndrome, irritable bowel syndrome, chronic headaches, interstitial cystitis, chronic pelvic pain, chronic tinnitus, whiplash-associated disorders, and vulvar vestibulitis.

IPSs commonly aggregate as "comorbid" conditions that are characterized by a complaint of pain as well as a mosaic of abnormalities in motor function, autonomic balance, neuroendocrine function, and sleep. In a very interesting article Diatchenko and coworkers from North Carolina, Florida, and Adelaide Australia review IPSs and proposed pathways of vulnerability that link these disorders

IPDs have been associated with a state of pain amplification and psychological distress. There is substantial individual variability in the relative contribution of pain amplification and psychological phenotypes to IPDs. The authors suggest that pain amplification and psychological distress, which are mediated by an individual's genetic variability and exposure to environmental events, represent two primary pathways of vulnerability that underlie the development of highly prevalent IPDs.

A well-established predictor of onset is the presence of another chronic pain condition, characterized by a state of pain amplification. For temporo-mandibular joint (TMJ) disorders not only is widespread pain a risk indicator for TMJ, but also for a lack of response to treatment. The condition is more likely to develop in those individuals more sensitive to noxious stimuli. A relatively high percentage of patients with IPDs show enhanced responses to noxious stimulation compared to controls. The enhanced pain perception may result from a disregulation in peripheral afferent and central nervous system pathways that produce dynamic, time-dependent changes in the excitability, and response characteristics of neuronal and glial cells.

This review advances the notion that we should look for similarities in chronic pain syndromes that may yield keys to treatment of this group of disorders. Because it is highly likely that IPDs share common underlying pathophysiological mechanisms it is expected that the same functional genetic variants will often be associated with comorbid IPDs and related signs and symptoms.

Diatchenko L, Nackley AG, Slade GD, Fillingim RB and Maixner W

Pain. 123(3):226-230, July 2006
doi:10.1016/j.pain.2006.04.015

UroToday.com Painful Bladder Syndrome Section

Written by Philip M. Hanno, MD, a Contributing Editor with UroToday.

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