title: Using perfusion MRI to measure the dynamic changes in neural activation associated with tonic muscular pain.
abstract: Knowledge regarding neural pain processing is primarily the result of studies involving models of brief cutaneous pain; however, clinical pain generally originates in deep tissue and is prolonged. This study measured the dynamic neural activation associated with a muscular pain model incorporating both acute and tonic states. Hypertonic saline (5% NaCl) was infused into the brachioradialis muscle of eleven healthy volunteers for 15min after an initial bolus of 0.5mL. Ten controls followed the same protocol with normal saline (0.9% NaCl). Magnetic resonance images of cerebral blood flow (CBF) were acquired using an arterial spin labelling method. The imaging volume extended from the thalamus to the primary somatosensory cortices, but did not include the brainstem and cerebellum. Using a numerical scale from 0 to 10, ratings of pain intensity peaked at 5.9+/-0.6 and remained near 5 for the remainder of the trial. Controls experienced minimal pain, reporting a peak value of 1.8+/-0.4. Significant CBF increases in rostral and caudal anterior insula bilaterally, anterior mid-cingulate cortex (aMCC), bilateral thalamus, and contralateral posterior insula were observed. The time courses of CBF revealed significant differences in the activation pattern during tonic pain. In particular, a more rapid return to baseline in aMCC versus insula was interpreted as a preferential decrease in the affective component of pain. This conclusion was supported by the strong correlation between pain intensity ratings and CBF in the contralateral insula (R(2)=0.911, p<0.01), which is a region believed to be responsible for pain intensity processing.
authors.affiliation: Lawson Health Research Institute, St. Joseph's Health Care London, 268 Grosvenor St., London, Ontario, Canada N6A 4V2 Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada Department of Anesthesia and Perioperative Medicine, The University of Western Ontario, London, Ontario, Canada Robarts Research Institute, London, Ontario, Canada.
authors.forename: Daron G
authors.initials: DG
authors.lastname: Owen
authors.forename: Collin F
authors.initials: CF
authors.lastname: Clarke
authors.forename: Sugantha
authors.initials: S
authors.lastname: Ganapathy
authors.forename: Frank S
authors.initials: FS
authors.lastname: Prato
authors.forename: Keith S
authors.initials: KS
authors.lastname: St Lawrence
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation*; D017711:Nonlinear Dynamics; D010146:Pain / Q000139:chemically induced / Q000473:pathology* / Q000503:physiopathology; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D012462:Saline Solution, Hypertonic / Q000009:adverse effects / Q000494:pharmacology; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D012462:Saline Solution, Hypertonic