Chronic low back pain and sick-leave: a functional magnetic resonance study

Chronic low back pain (CLBP) represents a problem in the occupational environment, often associated with disability, sick-leave demands, loss of productivity, anxiety, depression and high socioeconomic cost. The emergence of functional neuroimaging allowed new insights into brain structure and physiology in normality and chronic pain. While occupational related aspects are recognized as important risk factors for chronicity there have not been thus far evaluated by fMRI experiments. The overall objective of this study is to compare the neuronal correlates between groups of individuals CLBP with or without sick-leave demands.

A total of 74 individuals were divided into three groups: chronic low back pain with sick-leave demands [CLBP_L]; chronic low back pain without sick-leave demands [CLBP_NL]; individuals without pain or sick-leave demands [Control]. Functional magnetic resonance imaging was used to assess brain function during moderate acute pain stimulation task (thumb controlled pressure).

After acute painful stimulation, a higher brain response was found in the anterior cingulate and superior and medium frontal gyrus was observed in CLBP_NL vs. CLBP_L (p <  0,001) and increased brain response in the frontal pole and paracingulate region in control vs. CLBP_L (p <  0.001) during acute pain stimulation.

The modulation of acute pain participates in the mechanism propagating chronic pain perception. The lower activation in the superior frontal gyrus observed in the CLBP_L group compared to CLBP_NL, reinforces the idea of an already existing activation in this area.