Patients with fibromyalgia have been shown to suffer from hyperalgesia, or increased pain sensitivity, that exacerbates their existing symptoms. Now new research suggested that hypersensitivity to pain may be related to how their brain processes rewards and punishment.
In a new study from Arthritis & Rheumatism, the journal of the American College of Rheumatology, researchers found that patients with fibromyalgia have disrupted brain signals in areas of the brain responsible for reward and punishment.
Fibromyalgia syndrome (FMS) is a musculoskeletal pain condition characterized by widespread muscular and joint pain. Patients may also suffer from sleep disturbances, fatigue, cognitive difficulties, and a host of additional symptoms. Earlier research has suggested that these patients suffer from abnormal central nervous system pain processing, and a poor response to opioids, injections of medications, and topical pain treatments.
To study how brain function may play a role in pain processing, researchers from the Massachusetts General Hospital and Harvard Medical School in Boston studied 31 patients with fibromyalgia and 14 healthy controls. In order to measure their response to pain, researchers conducted pressure pain tests in which participants wore a cuff on their legs that tightened and loosened to apply more or less pain. Prior to an increase in pressure pain, different colors would appear on a screen, until participants were trained to expect pain with certain colors and pain relief with other colors. The participants rated their pain throughout the tests by pressing different buttons, and researchers monitored brain activity using a functional MRI scans.
The researchers found that during periods of pain anticipation or relief, the patients with fibromyalgia had had poorer responses in areas of the brain involved in sensory, cognitive, and affective pain regulating processes. In particular they noticed a difference a region located at the center of the brain called the ventral tegmental area (VTA), which is a group of neurons involved in processing punishment and reward. In healthy controls, the VTA was activated as participants anticipated and experienced pain, and deactivated during pain relief. But in patients with fibromyalgia the activation of the VTA was substantially reduced or inhibited, regardless of whether more or less pressure was applied.
These findings provide some clues as to why patients with fibromyalgia experience widespread chronic pain, and why so many fail to respond to opioid painkillers. In fact recent research has suggested opioids painkillers may do more harm than good for treating patients with fibromyalgia.
Loggia, ML, et al. Disrupted brain circuitry for pain-related reward/punishment in fibromyalgia. Arthritis & Rheumatism2013. DOI: 10.1002/art.38191).
Peters D. Pleasure and pain brain signals disrupted in fibromyalgia patients. Science Newsroom Wiley. Press Release. November 5, 2013.