Structural and functional changes in the brains of fibromyalgia subjects evaluated with single photon emission computed spectrometry and magnetic resonance imaging

Fibromyalgia (FM) is the most common chronic pain syndrome in the community. The absence of reproducible peripheral pathology has supported the hypothesis of abnormal central pain sensitisation/processing, with both psychological and biological theories invoked. Seminal work by Mountz et al. identified reduced regional cerebral blood flow (rCBF) in the thalamus and caudate nuclei. Our aim was to verify variation in rCBF of subjects with FM, and to refine its anatomical localisation and clinical correlation. Twenty-seven females with ACR criteria FM were matched with 22 age-matched, gender-matched and education-matched controls. Detailed physical and psychological inventories, 1.5T T₁/T₂ magnetic resonance imaging (MRI), and triple-headed ⁹⁹Tc single photon emission computed spectrometry (SPECT) scanning were performed. We have developed a colocalisation of SPECT-measured rCBF with MRI imaging, accurate to 2 mm. This allowed highly definable quantitative rCBF analysis using statistical parametric mapping (SPM). Initial studies identified a highly significant 16% reduction in rCBF of the pontine tegmentum/upper medulla, and less robust reduction in the thalamus. Clinical correlates favoured physical rather than psychological variables. In a subcohort of 11 FM subjects and 11 controls, rCBF has been measured twice over a 5-year period. None of the subjects were cured. rCBF remained significantly reduced in the pontine tegmentum and midbrain of FM subjects with normalisation of caudate and thalamic rCBF. In a novel analysis, SPM has been uniquely used for the detection of subvisual changes on T₁ and T₂ MRIscans. The MRI scans of 27 FM subjects were compared with those of 19 controls. Analysis of T₁ images identified a 6% reduction in signalamong FM subjects within the cerebellar tonsils and midbrain, the former in keeping with reports of Arnold–Chiari type 1 malformations. T₂ analysis identified widespread diffuse reduction in the white matterof FM subjects. Our studies have confirmed and localised objective abnormalities of rCBF among FM subjects. These changes probably reflect altered metabolic demands in pain processing centres, and for the first time have been shown to persist over time. Canonical and discriminant statistical analysis was not able to utilise these findings for diagnostic purposes. Additionally, subvisual abnormalities on MRI suggested structural and functional abnormalities within the brain.