APS Press Room
News Highlights from The Journal of Pain • August 2006
The Peer Review Journal of the American Pain Society
| For immediate release | Contact: Chuck Weber (847) 705-1802 |
PERIPHERAL AND CENTRAL CONTRIBUTIONS TO HYPERALGESIA IN IRRITABLE BOWEL SYNDROME
Donald D. Price, QiQi Zhou, Baharak Moshiree, Michael E. Robinson and G. Nicolas Verne
University of Florida Colleges of Medicine and Dentistry
Irritable bowel syndrome (IBS) is a common gastrointestinal disorder in which patients experience chronic abdominal pain associated with alterations in bowel patterns. The majority of IBS patients have low thresholds for visceral pain, increased intensity of sensations and widespread hyperalgesia. In this study, University of Florida researchers examined recent evidence for potential neural mechanisms that may contribute to somatic and visceral hyperalgesia in IBS patients.
The authors reported their evaluations of human and rat studies for this research clearly point to a spinal mechanism consistent with observations that IBS patients have enhanced responses to visceral and cutaneous stimuli throughout the pain matrix of the brain. However, they concluded it is unclear whether enhanced responses result from a facilitating mechanism in the brain, a spinal sensitization due to input from the rectum and/or colon, or a mechanism from the brain to the spinal cord or gut.
The study concluded that primary visceral and secondary cutaneous hyperalgesia in IBS patients involve a mechanism dynamically maintained by tonic input from abnormal receptors in the colon and /or rectum. Further secondary hyperalgesia is likely to be at least partly related to sensitization of spinal cord neurons and, therefore, might be similar to other persistent pain conditions, such as fibromyalgia and complex regional pain syndrome.
Commentary by Emeran A, Mayer, VA Medical Center West Los Angeles
In his commentary on the article, Mayer asked if the proposed role of abnormal tonic input to the spinal cord plays the central role in IBS pathology, what drives this abnormal input? He also inquired if there is a possible role for low-grade inflammatory changes in the intestinal mucosa. Mayar concluded that the research identifies a series of testable hypotheses that can be addressed by psychophysical and brain-imaging studies.
Commentary by Mickael Bouin, University of Montreal
Bouin believes the lack of a positive diagnostic test for IBS leaves hypersensitivity as the main basis for IBS diagnosis. But is hypersensitivity a biological marker or a condition of IBS? Also, Bouin asks if hypersensitivity is specific to IBS or gut-specific in IBS patients. Although this abnormality of the gut can be investigated in humans, he notes the lack of specificity and sensitivity precludes use of this symptom in clinical practice to make a positive diagnosis of IBS.
PREVALENCE AND CHARACTERISTICS OF BREAKTHROUGH PAIN IN OPIOID-TREATED PATIENTS WITH NONCANCER PAIN
Russell K. Portenoy, Daniel S. Bennett, Richard Rauck, Steven Simon, Donald Taylor Michael Brennan and Steven Shoemaker
From various university medical centers and supported by a grant by Cephalon, Inc.
Breakthrough pain is the transitory exacerbation of pain that occurs in otherwise controlled pain patients. It is estimated that up to 90 percent of cancer patients with chronic pain experience breakthrough pain. However, little is known about the prevalence and characteristics of breakthrough pain in populations with chronic noncancer pain treated with opioid medications. Researchers from nine different pain centers recruited 228 patients and administered a phone questionnaire. All patients had controlled baseline pain, and 74 percent said they experienced severe breakthrough pain. The most common syndrome was low-back pain.
The authors concluded that breakthrough pain is highly prevalent and varied in patients treated with opioids for noncancer chronic pain. They further noted that if future studies show adverse outcomes of breakthrough pain similar to cancer patients, clinicians will need to assess and manage this pain in noncancer patients as well.
SEX, GENDER AND AGE: CONTRIBUTIONS TO LABORATORY PAIN RESPONDING IN CHILDREN AND ADOLESCENTS
Cynthia D. Myers, Jennie C. I. Tsao, Dorie A. Glover, Su C. Kim, Norman Kirk and Lonnie K. Zeltzer
UCLA Pediatric Pain Program, David Geffen School of Medicine, UCLA
It is widely believed that gender socialization influences pain responding. Males typically are expected to withstand pain as evidence of being masculine and females accept pain as a normal part of life and are viewed as more willing to report pain. No published studies have examined the role of gender socialization in pain responses exhibited by children and adolescents. The goals of this study, therefore, were to examine the relationship of sex, gender socialization and age to responses to laboratory pain stimuli in healthy children and adolescents. Two-hundred-forty healthy subjects, equally divided by gender, participated in the study.
The authors reported there were no significant mean differences between girls’ and boys’ responses to laboratory pain. There was a trend for girls to exhibit lower tolerance for pressure pain, however. They concluded that the findings lend preliminary support to the view that gender socialization contributes to variability in responses to laboratory pain. This finding, however, does not appear to be stable across age, types of pain stimuli or parameters of pain response.