Fibromyalgia (FM) is a complex clinical syndrome that includes many symptoms beyond chronic pain. The studies that have addressed brain morphometry in FM have had very heterogeneous results. Thus, the question of which specific FM symptoms and clinical features – pain, but also psychological distress, sleep-related problems, health status, and medication intake – impact on brain morphometry remains open.
Here, we wanted to determine if brain changes in FM are "symptom-related" more than "diagnostic-related". We performed an observational study of 46 premenopausal women (23 FM patients and 23 age-matched healthy participants). Magnetic resonance images were analyzed using voxel-based morphometry and subcortical segmentation. We used multiple regression models to assess the associations between total and local brain volumes and FM clinical characteristics. Furthermore, we calculated associations between subcortical structures' shapes and volumes and FMS clinical characteristics.
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Larger psychological distress, anxiety, and sleepiness, and higher analgesic consumption accounted for 38% of FM patients' smaller total gray matter volume (GMV). For both groups, local decrements of GMV in the medial orbitofrontal cortex were associated to larger psychological distress. Local increases of GMV were positively related to pain scores (superior frontal gyrus), psychological distress (cerebellum), anxiety (medial orbitofrontal cortex), and sleepiness (frontal superior medial cortex). FM clinical characteristics were also associated to deformations in subcortical structures and volumes changes.
This study reveals that total and local GMV changes in FM go beyond the traditional "pain matrix" alterations. We demonstrated that brain morphology is altered by pain, but also by clinical characteristics that define the FM experience.
Source: Diaz-Piedra C, Guzman MA, Buela-Casal G, Catena A. The impact of fibromyalgia symptoms on brain morphometry. Brain Imaging Behav. 2015 Nov 28. [Epub ahead of print]