Coding of incisional pain in the brain: a functional magnetic resonance imaging study in human volunteers.
BACKGROUND
In this study, the activation of different brain areas after an experimental surgical incision was assessed by functional magnetic resonance imaging, and the pathophysiological role of distinct brain activation patterns for pain perception after incision was analyzed.


METHODS
Thirty male volunteers (mean age +/-SD, 25+/- 5 yr) received an experimental incision (4 mm) within the volar aspect of the right forearm using a ceramic scalper blade, and 14 volunteers (mean age +/- SD, 25 +/- 4 yr) received a sham procedure. Magnetic resonance images were taken before, during (0-2 min), and after incision or sham procedure (2-4.5, 4.5-10, 24-29, and 44-49 min) at a 3T scanner using a block design. Subjective pain ratings by a numerical pain scale were performed between the scans.


RESULTS
Functional magnetic resonance imaging analysis showed a distinct temporal profile of activity within specific brain regions during and after the injury. Lateralization (predominantly contralateral to the incision) and increased brain activity of the somatosensory cortex, frontal cortex, and limbic system were observed in subjects after incision, when compared with individuals receiving sham procedure. Peak brain activation occurred about 2 min after incision and decreased subsequently. A distinct correlation between evoked pain ratings and brain activity was observed for the anterior cingulate cortex, insular cortex, thalamus, frontal cortex, and somatosensory cortex.


CONCLUSIONS
These findings show different and distinct cortical and subcortical activation patterns over a relevant time period after incision. Pain sensitivity hereby has an influence on the activity profile. This may have important implications for encoding ongoing pain after a tissue injury, for example, resting pain in postoperative patients.
Pogatzki-Zahn
Esther M
EM
Department of Anaesthesiology and Intensive Care, University Hospital Münster, Albert-Schweitzer-Strasse 33, Münster, Germany. pogatzki@anit.uni-muenster.de
Wagner
Christian
C
Meinhardt-Renner
Anne
A
Burgmer
Markus
M
Beste
Christian
C
Zahn
Peter K
PK
Pfleiderer
Bettina
B
D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D016000:Cluster Analysis; D005543:Forearm Injuries / Q000503:physiopathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D011795:Surveys and Questionnaires; D055815:Young Adult
D010100:Oxygen