Central Mechanisms of Chronic Pain and Fatigue Subtitle: Functional Imaging of Brain and Spinal Cord

Chronic pain and fatigue are characterized by peripheral and central mechanisms including low pain thresholds, temporal summation, peripheral and central sensitization. This application will focus on central factors of chronic pain and fatigue. Functional brain imaging will be used to characterized brain and spinal cord abnormalities that contribute to the mechanisms of these disorders.

Chronic fatigue (ME/CFS) and fibromyalgia syndrome (FM) are a chronic musculoskeletal pain disorder that predominantly afflicts women. Frequently associated insomnia, cognitive abnormalities, and fatigue may lead to early disability. No consistent soft tissue abnormalities have been identified so far in these patients. The cause of these disorders is unknown, no highly effective treatment is available and the current methods of diagnosis are imprecise and unreliable. The Investigators previously used quantitative sensory testing to improve upon diagnoses of these disorders by supplementing the current procedure of manipulating defined pressure points by hand and noting the presence or absence of pain. The quantitative methods of evaluation involve repetitive application of brief, non-injurious thermal/mechanical stimulation that normally produces a moderate degree of temporal summation of sensation intensity. The patients and normal control subjects will verbally rate the magnitude of late sensations elicited by each stimulus, using a numerical scale. Chronic pain in these patients results, at least partially, from exaggerated activation of central N-methyl-D-aspartate (NMDA) receptors as a result of enhanced input from unmyelinated peripheral afferent nerve fibers supplying deep tissues. Temporal summation of second pain can lead to central sensitization with subsequent signs of hyperalgesia and allodynia. Functional brain imaging of ME/CFS and FM patients, as proposed in this study, will be used to document their ratings of repetitive experimental stimuli and the resulting pain augmentation. Successful completion of this study will provide a new method for the evaluation of chronic pain/fatigue mechanism and their response to therapy.