Editor’s comment: Oregon Health & Science University is currently raising funds for a study that will hopefully lead to a diagnostic marker for fibromyalgia and other chronic pain conditions. OHSU has been a leader in quality fibromyalgia research for many years.
Chronic pain is one of the most prevalent and debilitating of all diseases. Yet as of today, we still can’t diagnose and treat the many patients suffering from this condition. These patients are often stigmatized as narcotic seeking or malingering because of our inability to see (and therefore validate) their chronic pain like a physician does for heart disease (with an EKG or echo), diabetes (with a blood test), or lung disease (with an X-ray).
We are designing this study to unmask the brain changes that may be key to the development and progression of chronic pain. We recently found that fibromyalgia patients are more sensitive to light than their healthy counterparts. We think this is related to activation of their brain’s pain-sensitive regions. To prove this, we would like to use an advanced type of imaging called functional MRI to see if light produces changes in these pain centers.
We expect light to produce changes in fibromyalgia patients’ pain-specific brain regions. This would aid tremendously in the diagnosis and validation of their chronic pain. This ultimately would reduce much of the stigma and suffering these patients go through, and lead to earlier, more specific treatments.
Pain is defined as a sensory experience that under normal conditions is evoked by injury to bodily tissue. Our understanding of acute pain is relatively advanced. We know that injury activates a specialized class of afferent neurons called nociceptors. Nociceptor activation in turn excites defined spinal cord circuits that project to supraspinal targets, resulting in coordinated activation of a distributed cortical network often referred to as the “pain matrix. This network includes anterior cingulate and prefrontal cortex, the insula, and variably, primary and secondary somatosensory cortices. Acute pain can usually be controlled adequately using analgesic drugs or by blocking specific nociceptor pathways.
However, much clinically significant chronic pain persists in the absence of identifiable injury or inflammation. This pain without detectable injury is generally attributed to “central sensitization,” a process by which spinal and supraspinal nociceptive pathways develop an abnormal sensitivity to non-injurious peripheral stimuli. Innocuous stimuli are therefore experienced as pain. The concept of central sensitization is well-supported in animal studies, which use electrophysiological approaches to document altered excitability of dorsal horn nociceptive neurons, as well as changes in brainstem pain-modulating systems, in preclinical models of persistent pain. The usual approaches to pain management are less effective or ineffective, and can have unacceptable side effects with chronic use.
Unfortunately, central sensitization cannot be demonstrated directly in patients, since invasive procedures are not possible. Our long-term goal as pain-focused investigators is to identify and validate markers for central sensitization, and to use these markers as tools in developing and directing effective treatments for patients with chronic pain.
The present translational proposal is based on two intriguing preliminary findings that suggest that photosensitivity could be a useful marker for central sensitization in chronic pain patients. First, we recently found that patients with fibromyalgia, a common pain condition in which there is no evidence of peripheral nociception, demonstrate profound photosensitivity compared to controls. Second, we found that in rodents, brainstem pain-facilitating neurons respond to light in some chronic pain models where central sensitization is thought to be important. The overarching hypothesis driving the present proposal is that light exposure activates pain-facilitating neurons in patients with fibromyalgia, contributing to abnormal pain sensitivity. If so, light exposure should activate the pain matrix in these patients.
Specific Aim: Using functional MRI, test the hypothesis that a light stimulus sufficient to elicit discomfort in fibromyalgia patients will activate the pain matrix in these individuals, but not in normal controls.
Chronic pain is now recognized to represent a “changed brain state.” The proposed studies are a step towards a practical biomarker that could be used to identify central sensitization as an important in specific pain states, and to guide research towards treatments that target the underlying mechanism.
Why is this important?
This proposed study would advance our ability to diagnose and validate hidden changes that maintain chronic pain. Ultimately, this would lead to a marker for diagnosing pain and eventually treating the underlying cause.
Who will benefit from the results of this project?
Any patient with chronic pain can potentially benefit from our study. Specifically, fibromyalgia patients who have often been told that there are not objective lab tests that allow doctors to see their chronic pain. This study may provide such missing visible evidence that will help doctors understand that the symptoms that their patients have are clearly based in biological changes in the brain.
For more information about the researchers or to donate to this project, go to “Light: A Window to Pain in the Brain”