A disruption in brain signals may contribute to increased pain sensitivity in fibromyalgia patients, according to new research.
A small study published in the journal Arthritis & Rheumatism suggests that this altered brain processing may contribute to hyperalgesia – causing widespread pain and a lack of response to opioid pain medication.
“In patients with fibromyalgia there is an alteration in the central nervous system pain processing and a poor response to topical pain treatments, trigger point injections and opioids,” said lead author Dr. Marco Loggia from Massachusetts General Hospital and Harvard Medical School in Boston.
“Our study examines the disruption of brain function involved in the individual experience of pain anticipation and pain relief.”
Researchers enrolled 31 patients with fibromyalgia and 14 healthy participants. Magnetic resonance images (MRI) of the brain and cuff pressure pain stimulation on a leg were performed on all subjects. During the MRI, participants received visual cues alerting them of impending pain onset (pain anticipation) and pain offset (relief anticipation).
The MRI images showed that during both pain anticipation and pain relief, fibromyalgia patients had a less robust response in the parts of their brains involved in sensory, affective, cognitive and pain regulating processes.
In healthy subjects, the ventral tegmental area (VTA) — a group of neurons in the center of the brain involved in the processing of reward and punishment — displayed activation during pain anticipation and stimulation, and then deactivated when a participant anticipated pain relief.
For fibromyalgia patients, however, the VTA responses during periods of pain, and anticipation of pain and relief, were significantly reduced or inhibited.
“Our findings suggest that fibromyalgia patients exhibit altered brain responses to punishing and rewarding events, such as expectancy of pain and relief of pain,” said Loggia.
“These observations may contribute to explain the heightened sensitivity to pain, as well as the lack of effectiveness of pain medications such as opioids, observed in these patients. Future studies should further investigate the neurochemical basis underlying these dysfunctions.”
One possible explanation for the reduced response in fibromyalgia patients is that they always experienced some degree of ongoing pain, and never felt the full benefit of pain relief as the healthy participants in the study.
The National Institutes of Health estimates that 5 million Americans suffer from fibromyalgia, a poorly understood disorder characterized by chronic deep tissue pain, fatigue, headaches, depression and lack of sleep. There is no known cure and many medications prescribed to treat fibromyalgia are ineffective.