Functional MR imaging analysis of pain-related brain activation after acute mechanical stimulation

BACKGROUND AND PURPOSE: Most studies concerning imaging of pain processing have used thermal, chemical, or electrical nociceptive stimulation. The aim of the present study was to determine the cortical representation of mechanical pain. For this, using functional MR (fMR) imaging at 1.5 T, we compared activation patterns during painful and nonpainful tonic mechanical stimulation in healthy volunteers. METHODS: Eleven right-handed subjects ranging in age from 21 to 46 years underwent gradient-echo echo-planar fMR imaging while quantified tonic pressure was applied to the first metacarpophalangeal joint. Imaging parameters were 3000/60 (TR/TE) with a 5-mm section thickness in a 7.30-minute sequence with 2 3 90 seconds of painful stimulation interleaved with 3 3 90 seconds of nonpainful stimulation. Functional images were processed using dedi-cated IDL software. RESULTS: Mechanical tonic nociceptive pressure was associated with activation of the pri-mary somatosensory cortex contralateral to the hand stimulated and variable, often bilateral activation of the secondary somatosensory, temporal, anterior and posterior cingulate, insular, and prefrontal cortexes. Thalamic activation was inconsistent and always contralateral t