By Phoebe Starr
Washington, DC—The way patients with fibromyalgia experience pain may be a result of abnormal pain signal processing associated with reduced opioid receptor binding, according to a study presented during the 2012 meeting of the American College of Rheumatology.
This study is the first to demonstrate the connection between µ-opioid receptor binding and the brain’s response to the pain of fibromyalgia, noted lead investigator Richard Harris, PhD, Assistant Professor, Department of Internal Medicine, University of Michigan, Ann Arbor. “In patients with fibromyalgia, the main inhibitory mechanisms are not working correctly, specifically the opioid receptors within the brain,” he told listeners.
The study was based on the assessment of changes in blood oxygenation by functional magnetic resonance imaging in 18 female patients with fibromyalgia who were opioid-naïve. Patients received a painful stimulus to the thumb in varying intensity, and pain was measured by the short-form McGill Pain Questionnaire.
Patients were treated with acupuncture and placebo acupuncture for pain reduction before and after exposure to the painful stimuli. The researchers also measured µ-opioid receptor binding before and after the painful stimuli.
“When opioid receptor binding went down, the evoked brain pain response went up in key brain regions that are involved in pain processing, such as the insula and amygdala,” Dr Harris observed. He proposed 2 possible explanations—either that the receptors were downregulated or that activating the receptors actually caused the pain.
Dr Harris said that the results appeared to be paradoxical. “We found that patients with fibromyalgia either have too few micron receptors in their brains, or that when the micron receptors activate, they cause pain instead of lessening pain.” These findings may explain the lack of response to opioids in patients with fibromyalgia.
Sleep, Relationships, Cognition
Several studies by another group of investigators led by Robert S. Katz, MD, Professor, Rush University, Chicago, IL, show that fibromyalgia has negative effects on physical, cognitive, and emotional functioning.
In a small study of 16 patients with fibromyalgia (10 women, 6 men) and 3 controls, patients with fibromyalgia exhibited many more nocturnal awakenings and poor sleep efficiency. They also moved around at night quite a bit more than the controls. The research suggests that these sleep disturbances may prevent adequate rest of the patients’ tired and painful muscles.
In the study, patients were given armband devices to monitor their sleep at home on 4 consecutive nights. The researchers measured the duration of sleep, sleep efficiency, and the number of awakenings, and then compared these findings with patient self-reported sleep patterns on a visual analog scale.
The ability to monitor patients’ sleep at home without the patient having to spend a night in a sleep laboratory is an inexpensive way to measure sleep quality, said the investigators.
According to another study, fibromyalgia interferes with the ability to work. Pain, fatigue, and cognitive dysfunction were cited as the primary factors that limited the ability to work.
Almost half (48.7%) of the 76 patients in this study (mostly women) were not working, 13.2% were working part time, and 38.2% were working full time. More than half (51.4%) of the patients who were not working cited fibromyalgia as the reason.
The patients who were able to continue working credited several strategies, including being persistent, staying busy, maintaining a positive attitude, exercising, eating well, and getting enough sleep. The more disabled patients felt incapable of using these approaches.
Patients with fibromyalgia reported more problems with language and spatial tasks than the controls without rheumatic diseases in a study based on assessment via questionnaires, suggesting that learning disabilities may be another part of a dysfunctional central nervous system in these patients.
The study included 89 patients with fibromyalgia, 39 patients with rheumatoid arthritis (RA), 23 patients with systemic lupus erythematosus (SLE), and 14 controls with no rheumatic disease.
The fibromyalgia group had significantly worse reading and oral expressive language scores (P = .001) compared with controls. They also scored worse in all 4 areas than the RA and SLE groups (range, P <.001-.007).
Fibromyalgia takes a toll on relationships, according to an internet-based study of 763 female respondents with self-described fibromyalgia. The results were drawn from the part of a survey on the effect of fibromyalgia on relationships with family, friends, and coworkers. Spouses were perceived as the most supportive (59.1%) compared with other relationships; however, serious strains in all relationships were reported.
Fibromyalgia had the most negative effects on relationships with coworkers, in-laws, and the subjects’ parents. The investigators suggested that better public education about the invisible but real symptoms of fibromyalgia may improve these relationships.