Chronic low back pain (CLBP) is a major health issue, yet its underlying mechanisms remain unknown. Studies have demonstrated the importance of emotion and cognition in chronic pain; however, the relevant brain physiology in magnetic resonance imaging (MRI) studies are unclear in CLBP populations. Therefore, this review aimed to identify MRI brain changes and examine their potential relationship with emotional and cognitive processes in CLBP.
A systematic search was conducted in 5 databases. Studies that recruited adult, CLBP populations, and used brain MRI protocols were included.
In total, 55 studies met the inclusion criteria. Of the structural MRI studies, 10 of 15 studies found decreased gray matter and 7 of 8 studies found white matter changes in CLBP groups compared with controls. Fourteen resting-state functional MRI studies all reported differences between CLBP and control groups in the default mode network. Interestingly, only 3 of 10 functional MRI studies observed significant differences during noxious stimulation between CLBP and control groups, whereas 13 of 16 studies observed significant brain activation differences in CLBP groups during various external tasks. Finally, there were 3 studies that observed a degree of recovery in functional connectivity following intervention.
The brain changes in CLBP groups were mainly observed in areas and networks important in emotion and cognition, rather than those typically associated with nociception. This supports the understanding that emotional and cognitive processes may be the core contributor to the CLBP experience; however, future studies need to explore these processes further.
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*Central Clinical School, Monash Alfred Psychiatry Research Centre, Monash University
†Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Vic., Australia
S.K.N. is a recipient of an Australian Postgraduate Award. D.M.U. holds a National Health and Medical Research Council Career Development Fellowships (Clinical Level 1 #1011975). P.B.F. is supported by National Health and Medical Research Council (NHMRC), Canberra, ACT, Australia; Practitioner Fellowship (#1078567). B.M.F. is supported by a National Health and Medical Research Council Early Career Fellowship (#1070073). The remaining authors declare no conflict of interest.
Reprints: Sin Ki Ng, BBNSc (Hons), Central Clinical School, Monash Alfred Psychiatry Research Centre, Monash University, 4/607 St. Kilda Road, Melbourne, Vic. 3004, Australia (e-mail: email@example.com).
Received January 4, 2017
Received in revised form June 8, 2017
Accepted July 3, 2017