Fibromyalgia is a chronic syndrome defined by widespread muscle pain, fatigue, sleep dysfunction and cognitive dysfunction. Fibromyalgia pain dysfunction involves an increased sensitivity to pain known as hyperalgesia. New research suggests that a disruption of brain signals for reward and punishment contributes to this increased pain sensitivity. The results published in Arthritis & Rheumatism, a journal of the American College of Rheumatology, suggests that it is this altered brain processing that could contribute to the widespread pain felt by people with fibromyalgia as well as the lack of response to opioid therapy in patients.
In people“’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.” (National Pain Report)
The study involved 31 subjects with fibromyalgia and 14 healthy controls. Functional magnetic resonance imaging (MRI) and a cuff pressure pain stimuli on the leg were preformed on all patients. During the MRI subjects received visual cues which would inform them of pain onset (pain anticipation) and pain offset (relief anticipation).
The MRI results showed that with both pain anticipation and pain relief the fibromyalgia subjects displayed less robust responses in the regions of the brain involved in sensory, affective, cognitive and pain regulating processes.
In particular there is a group of neurons in the centre of the brain involved in the processing of reward and punishment called the ventral tegmental area (VTA) where the fibromyalgia patients responses during periods of pain, anticipation of pain and anticipation of relief, were significantly inhibited. In the healthy subjects the VTA responses displayed activation during pain anticipation and pain, and then deactivation when the subject anticipated pain relief.
Dr. Loggia states, “Our findings suggest that fibromyalgia patients exhibit altered brain responses to punishing and rewarding events, such as expectancy of pain and relief of pain. 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.”
The features of fibromyalgia pain are the abnormal pain processing leading to a lower pain threshold in the brain causing the brain to react faster to pain stimulus. This is referred to as hyperalgesia. The pain reaction is more intense. In fact, it can be so intense even a light touch to the skin is painful, called alloyinia. For the very same stimulus someone with FM will have more enduring pain than someone without. The pain will simply last longer, as the brain continues to send out the pain signal even when it is not required. People with FM have an estimated three times as much levels of a brain chemical called Substance P which is responsible for sending the pain messages to the body. Levels of dopamine can be low in response to pain. In a normal situation when the brain determines a pain stimulus is nonthreatening it flushes the brain with dopamine to reduce the pain level felt by the person. Some studies with fibromyalgia subjects this does not occur and the pain stimulus continues at the same pain level. It is clear there is pain dysfunction on a neurological level that leads to increased sensitivity and longer duration of pain in people with fibromyalgia. However given the nature of this chronic pain dysfunction it does seem this might effect the anticipation of pain and anticipation of pain relief. In fact, anticipation of pain relief might be inhibited simply because it is never felt to the degree it would be in a control subject. Whether this disruption of brain signals in the VTA has an impact on the hyperalgesia or is a result of the condition itself is difficult to determine based on the amount of factors causing pain dysfunction. There is, however, a lot more involved in all chronic pain beyond the simple sensation of pain itself. Many areas of the brain are involved in the pain process and therefore distorted when chronic pain begins.