Aim: Functional MRI (fMRI) can measure changes in regional cerebral blood flow associated with painful stimulation. Previous fMRI studies in fibromyalgia (FM) have indicated differences in pain processing, suggesting supraspinal pain amplification. This study examined the effect of an important clinical construct in chronic pain patients – perceived locus of control of pain – on regional blood flow patterns associated with painful pressure.
Methods: Subjects (n=21) with fibromyalgia completed the Beliefs in Pain Control Questionnaire (BPCQ). Pressure was applied to the left thumb nail bed in alternating 30 s blocks at innocuous and painful intensities for 10 min.
Echo-planar images of 50 horizontal slices of 3mm thickness were obtained with a Siemens 1.5 Tesla scanner every 5 s during stimulation. The fMRI data were corrected for head motion, spatially smoothed with a Gaussian filter (FWHM= 6mm3) and intensity normalized. Mean differences in fMRI signal between the painful and innocuous conditions were computed and transformed into standard space for inter-subject analyses and anatomical localization. Correlations were computed at each voxel in the brain between the mean difference value and BPCQ subscale scores (Internal, Powerful Doctors, Chance). Correlations significant at p < 0.05 after RESEL correction for multiple comparisons are reported here.
Results: Each of the BPCQ subscale scores were related to the average increase in blood flow in discrete cerebral regions as assessed with fMRI from the innocuous to painful condition – Internal with the right SII (r = 0.84), Powerful Doctors with bilateral inferior parietal gyri/BA40 (Right r = 0.82, Left r = 0.75), Chance with right superior temporal gyrus (STG)/BA 22 (r = 0.82).
Conclusions: Endorsing a strong internal locus is associated with greater levels of pain related activity in SII possibly reflecting differential degrees of stimulus labeling and selective attention. Increased parietal activity associated with PD scores may indicate recruitment of cortico-limbic pathways involved in pain hedonics and affective responses. The implications of the relationship between C and STG activation are not readily apparent. The results of this study support the hypothesis that beliefs about pain-control influence central processing of noxious stimulation in FM.
Disclosure: This study was supported by Army grant 17-00-6042.