title: Structural and functional brain abnormalities in chronic low back pain: A systematic review.
abstract: OBJECTIVE
  The purpose of this systematic review is to analyze the available literature on structural and functional brain abnormalities in chronic low back pain (CLBP) using several brain magnetic resonance imaging (MRI) techniques.
  
  
  METHODS
  PubMed and Web of Science were systematically screened for relevant literature using different combinations of keywords regarding structural and functional brain imaging techniques in patients with CLBP. Reference lists of included articles were hand-searched for additional literature. Eligible articles were assessed on risk of bias and reviewed by two independent researchers.
  
  
  RESULTS
  The search query returned 27 articles meeting the inclusion criteria. Methodological quality varied from poor to good. A total of 10 studies evaluated structural gray matter changes. There is conflicting evidence in global gray matter changes, with both increases and decreases shown in different studies. Gray matter changes were demonstrated in specific brain regions. Structural white matter changes were reported in five studies. There is conflicting evidence in total white matter volume due to both increases and unchanged white matter. Several regional differences were identified in which white matter changes were shown. Functional organization during rest was evaluated in 10 studies. CLBP patients showed increased activation in specific regions, together with a disrupted default mode network. A total of six studies evaluated brain activity in response to a nociceptive stimulus. Findings suggest that patients demonstrated increased activity in pain-related regions, and decreased activity in analgesic regions.
  
  
  CONCLUSIONS
  Overall, there is moderate evidence for regional changes in gray and white matter, together with an altered functional connectivity during rest and increased activity in pain-related areas following painful stimulation, evidencing an upregulated pain matrix. More longitudinal research is needed to clarify the temporal relationship regarding pain and neuroplastic changes, and integration of different brain imaging techniques is warranted.
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium; Department of Human Physiology, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Department of Physiotherapy, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; "Pain in Motion" International Research Group.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Kregel
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium; "Pain in Motion" International Research Group; Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.
authors.forename: Mira
authors.initials: M
authors.lastname: Meeus
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium; Department of Human Physiology, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Department of Physiotherapy, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; "Pain in Motion" International Research Group.
authors.forename: Anneleen
authors.initials: A
authors.lastname: Malfliet
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium.
authors.forename: Mieke
authors.initials: M
authors.lastname: Dolphens
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: Danneels
authors.affiliation: Department of Human Physiology, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; Department of Physiotherapy, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium; "Pain in Motion" International Research Group.
authors.forename: Jo
authors.initials: J
authors.lastname: Nijs
authors.affiliation: Department of Rehabilitation Sciences and Physiotherapy, Ghent University, De Pintelaan 185 3B3, Ghent 9000, Belgium. Electronic address: barbara.cagnie@ugent.be.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cagnie
mesh_terms: D001921:Brain / Q000473:pathology* / Q000503:physiopathology; D001931:Brain Mapping; D059350:Chronic Pain / Q000473:pathology* / Q000503:physiopathology; D006801:Humans; D017116:Low Back Pain / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D059906:Neuroimaging
keywords: (rs)-fMRI; Back pain; Brain activity; Chronic pain; Diffusion tensor imaging; Functional connectivity; Gray matter; Pain matrix; White matter