(HealthDay News) – Greater connectivity between two areas of the brain increases the likelihood that subacute back pain will not recover and will become chronic instead.

Marwan N. Baliki, PhD, from the Northwestern University Feinberg School of Medicine in Chicago, and colleagues performed brain scans at study entry and followed pain and brain markers over a one-year period in 40 patients who previously had an episode of subacute back pain lasting 4–16 weeks.

The researchers found that, compared with patients who recovered from their pain, patients whose pain became chronic had greater connectivity between the medial prefrontal cortex (mPFC) and the nucleus accumbens (NAc), an area underlying reinforcement learning. These patients also had loss of gray matter density in the bilateral striatum and insula and in the left sensorimotor cortex. Patients with persistent pain had significantly greater positive functional connectivity in the NAc at baseline and one year. Greater functional connectivity of the NAc with the mPFC at baseline was predictive of persistent pain.

“Here we show that the corticolimbic mPFC-NAc connection is an accurate predictor of the transition from subacute to chronic pain,” Baliki and colleagues conclude. “That motivation-valuation circuitry predicts pain persistence raises the intriguing possibility that, as with positive reinforcement learning, the NAc contributes to an aversive teaching signal that leads to sustained pain intensity over time following a static peripheral injury.”

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