Cerebral Response To Actual And Anticipated Pain

Researchers in Liverpool used fMRI mapping techniques to measure neural activity and cortical reorganisation in response to actual and anticipated pain. Three patient groups were included in the study: 17 healthy controls made up group C, and 20 chronic lower back pain patients that were subdivided into 8 patients in Group B who displayed maladaptive pain behaviour including Waddell signs (indicating a non-organic cause of their pain), and 12 patients made up group A where no such behaviour patterns were displayed.


Inside the MR scanner patients were subjected to three possible stimuli: thermal stimulation of the hand; electrical stimulation of the lower back (visual analogue score, VAS, of 7/10) or elevation of the leg to an uncomfortable position. Leg movement was accompanied by a visual cue: green signified certain pain, red accompanied no pain and yellow indicated an uncertain movement. During each stimulation or movement cortical activity was monitored and mapped.


Groups A and B (all back pain patients) both registered greater increase in activity than group C (healthy controls) in the left inferior parietal lobe (IPL) when stimulated by thermal pain in the right hand - as compared to activity at rest. Similarly, Groups A and B showed significantly more activation in response to the green light cue for imminent painful elevation of the leg than they did for the yellow light cue for an unpredictable movement - and this time in the right IPL, superior parietal lobe (SPL) and the primary sensorimotor cortex.


However, most significant was the overall comparison of response by Group A and group B (patients with non-organic pain and maladaptive behaviour). The former displayed significantly higher scores in catastrophising, disability and anxiety - suggesting that somato-sensory reorganisation increases with chronicity of back pain and that prolonged pain may directly generate cortical hyper-responsiveness.


paineuropenewswire