Chronic back pain.. Study reveals a surprising role for the brain

A recent study conducted by researchers at the University of California, San Diego, revealed that episodes of chronic lower back pain triggered by movement are not limited to the physical sensation of pain; they also activate a brain network responsible for self-referential thinking and the retrieval of personal experiences.

The study found that individuals suffering from chronic back pain may recall previous painful experiences when preparing to move, thereby increasing their pain expectations and prompting them to move cautiously to avoid recurrence.

The study involved 114 participants with chronic lower back pain, and its findings were published in the British Journal of Anaesthesia, providing new evidence of the role that brain processes linked to memory and personal experiences play in shaping the pain experience.

Researchers asked participants to perform a leg-lifting test, which is used to elicit back pain, while monitoring changes in cerebral blood flow using specialized functional magnetic resonance imaging (fMRI) technology.

During the test, pain intensity increased by approximately 23 percent, and the level of distress associated with the pain rose by about 26 percent, compared to pre-test levels.

This was accompanied by activity in brain regions involved in processing pain, sensation, and movement, as well as in key areas of the “default mode network.”

This network is associated with internal thought, retrieval of personal experiences, and self-reflection, and its activity typically decreases when a person directs their attention to a prominent external stimulus, including certain types of acute pain.

However, movement-induced back pain episodes were associated with increased activity in parts of this network. In contrast, painful thermal stimuli were linked to decreased activity in the network, according to the university’s explanation of the results.

Researchers also found that participants who reported more severe chronic pain exhibited stronger functional connectivity between this network and a sensory region that processes signals related to the back.

The results suggest an overlap between the processing of painful sensations and brain processes related to the self, without determining the cause of this overlap.

According to a university statement, co-researcher Fadel Zidan believes that the experience of chronic pain may be influenced by the anticipation of an episode, recovery from it, and past experiences such as the inability to participate in usual activities or fear of movement to avoid pain.

The analysis is observational and relies on data collected before therapeutic interventions within a broader trial. Therefore, while it can identify correlations between brain activity and pain, it cannot determine the direction of the relationship or explain all causes of chronic lower back pain.

The study adds that understanding pain episodes may require looking not only at the sensation itself but also at the surrounding expectations and experiences, in order to understand how patients experience it.