Pain depends on the interaction of cognitive, and emotional factors. Individuals with negative coping strategies such as catastrophizing are prone to develop chronic pain syndromes, and poor functional outcomes. This maladapted behavior may be caused by abnormalities in attention systems and amplification of pain processing. Low back pain (LBP) is a disabling pain syndrome, but it is poorly known how catastrophizing affects brain activity. To explore catastrophizing neural correlates in LBP, we performed an fMRI study to verify the central pain system (pain matrix), and anticipation responses. Under unpredictable stimuli, we expected to see catastrophizing LBP showing lower ability to disengage attention to pain and lower pain threshold.

We studied 43 LBP and 27C subjects. LBP responded catastrophizing questionnaires (FABQ, CSQ). We used a pressure-pain device, to deliver stimuli in the thumbnail. Pain thresholds detected a priori, for moderate pain. Subjects performed 2 event-related fMRI experiments: 1 - Supraliminal Pain for the pain matrix study; 2 – Variable Pain for anticipation at unpredictable stimuli. T2* images acquired in a 3T Siemens scanner. FMRI data was preprocessed and carried out using FSL tool. Corrected cluster significance threshold: P=0.05.

Both groups were similar for demographics. LBP had lower threshold for pressure stimulus. Both groups activated pain matrix areas, and had the same pattern during anticipation. When covarying with FABQ during experiment 2, LBP showed greater posterior cingulate cortex activation, indicating that in LBP, FABQ reduces brain activity.

LBP had lower pain threshold, suggesting central sensitization. Although both groups activated the pain matrix and had the same anticipation pattern, catastrophizing LBP had decreased activity in posterior cingulate cortex, suggesting negative coping skill influences pain appraisal in anticipation. The area belongs to the attention system and antinociception pathways in healthy subjects. Our results are in line with previous data showing greater posterior cingulate activity in low catastrophizers.