Differences in low back pain behavior are reflected in the cerebral response to tactile stimulation of the lower back.
METHODS
Two groups of patients with chronic low back pain (cLBP) were scanned with functional magnetic resonance imaging during stimulation of the lower back; those showing 4 or 5 positive Waddell signs (WS-H) and those showing 1 or none (WS-L) as an index of pain-related illness behavior.


OBJECTIVE
We hypothesized that patients showing good versus poor adjustment to cLBP mobilize cortical affective-cognitive functions differently in response to sensory stimulation and show increased reorganization of somatosensory cortex corresponding to the back.


BACKGROUND
Some patients with cLBP go on to develop significant disability while the majority do not, and physical disease or psychosocial factors alone do not account for the difference. Neuroimaging studies have suggested abnormalities in cortical pain modulation systems can lead to variable pain and behavioral responses, which may account for these differences. METHODS.: Fifteen WS-L and 13 WS-H patients were scanned with functional magnetic resonance imaging while receiving intense tactile stimulation to the lower back. Questionnaire measures of psychosocial function were also collected.


RESULTS
There were no significant differences in cLBP duration or lumbar stimulation tolerance threshold between the 2 groups. Significantly more activation was seen in the WS-L versus WS-H group in regions previously associated with normal affective-cognitive processing of sensory input including posterior cingulate and parietal cortices; the magnitude of this activation negatively correlated with catastrophizing scores. WS-H patients showed a modest medial shift in primary somatosensory cortex activation relative to the WS-L group.


CONCLUSIONS
Successful adjustment to cLBP is associated with a patient's ability to effectively engage a sensory modulation system. In patients in whom such activation does not occur, subjective lack of control maypredispose to altered affective and behavioral responses with poor adjustment to pain. Pain experience may be furthermodified by reorganization of somatosensory cortex, contributing to maintenance of the chronic pain state.
Lloyd
Donna
D
Magnetic Resonance and Image Analysis Research Centre (MARIARC), University of Liverpool, Liverpool, UK.
Findlay
Gordon
G
Roberts
Neil
N
Nurmikko
Turo
T
D000223:Adaptation, Psychological; D000328:Adult; D000339:Affect; D000368:Aged; D001931:Brain Mapping; D002908:Chronic Disease; D003071:Cognition; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000473:pathology / Q000503:physiopathology / Q000523:psychology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D017288:Pain Threshold; D010812:Physical Stimulation; D013003:Somatosensory Cortex / Q000473:pathology / Q000503:physiopathology*; D011795:Surveys and Questionnaires