The use of functional magnetic resonance Imaging in evaluation of Fibromyalgia

Fibromyalgia is a chronic syndrome characterized by generalized pain and stiffness in skeletal muscles and surrounding tissues. Fibromyalgia causes sufferers to have a heightened pain perception leading to the body being oversensitive to pain stimuli.1 Common symptoms of fibromyalgia include pain, stiffness,fatigue, sleep disturbance, irritable bowel syndrome, concentration and memory problems.2 There is no known cause or cure but there are effective treatments aimed at controlling the various symptoms.1 As there is no definitive diagnostic test for fibromyalgia and the presenting symptoms can be vague and confounding, patients are usually defined in the health system as ‘hypochondriacs’. Functional imaging can show the anatomical regions of the brain that activate in response to a pain stimulus.3, 5 Functional mri (fMRI) is a technique based on the physiological effect termed BOLD (blood oxygenation level dependent). BOLD detects changes in the magnetic susceptibility of tissues reflective of the oxygen levels in the localized blood vessels in the brain.4 Aim -Hypothesis tested was that the chronic pain group would reveal a different pattern of brain activity compared to control group due to a heightened pain perception.Methods - 8 control (pain free) and 11 chronic pain participants (8 fibromyalgia patients, 3 patients with persistent pain > 3 months) were imaged using a block paradigm design fMRI. Patients were imaged on a 3T GE Signa Excite magnet (Milwaukee, WI) with an eight channel Medical devices head coil. The fMRI sequence utilized a single shot EPI (TR -3000ms, TE – 35 ms, 24cm FOV, 4.0mm slices, no slice gap, 39 slices, 128 x 128 matrix) 5 minute 15 second acquisition. The imaging sequence consisted of 5 cycles of pain/rest periods, 30 seconds on (active) then 30 seconds off (rest). A 2kg pressure pain stimulus, with a contact diameter of 2cm, was applied on the anterior surface of the right mid-thigh. Analysis of the images was processed using MATLAB version 7.11 (The Mathworks Inc, Natick, Mass) and Statistical Parametric mapping Software (SPM8; The Wellcome Department of Imaging Neuroscience, London). The 2kg weight was chosen to allow the patients in the chronic pain group to tolerate the stimulus for the functional imaging. This study was conducted with ethics approval.Results – Table One summarizes areas with significant fMRI activations (p<0.01) for the chronic and control group. There were three significant areas where chronic pain sufferers had more activation than the control group (p<0.001). Resultant activation maps for the respective groups are shown in Figure 1.