Relationship between chronic pain and brain reorganization after deafferentation: A systematic review of functional MRI findings

Abstract

Background: Mechanisms underlying the development of phantom limb pain and neuropathic pain after limb amputation and spinal cord injury, respectively, are poorly understood. The goal of this systematic review was to assess the robustness of evidence in support of "maladaptive plasticity" emerging from applications of advanced functional magnetic resonance imaging (MRI).

Methods: Using MeSH heading search terms in PubMed and SCOPUS, a systematic review was performed querying published manuscripts.

Results: From 146 candidate publications, 10 were identified as meeting the inclusion criteria. Results from fMRI investigations provided some level of support for maladaptive cortical plasticity, including longitudinal studies that demonstrated a change in functional organization related to decreases in pain. However, a number of studies have reported no relationship between reorganization, pain and deafferentation, and emerging evidence has also suggested the opposite - that is, chronic pain is associated with preserved cortical function.

Conclusion: Based solely on advanced functional neuroimaging results, there is only limited evidence for a relationship between chronic pain intensity and reorganization after deafferentation. The review demonstrates the need for additional neuroimaging studies to clarify the relationship between chronic pain and reorganization.

Keywords: Amputation; Cortical reorganization; Functional imaging; Neuropathic pain; Phantom-limb pain; Spinal cord injury.

Fig. 1

Diagram of the review procedure.

Fig. 2

Forest plot of mean age, time since deafferenation, and pain rating for each study, and the grand weighted average for each parameter. The results are displayed in mean ± standard deviation. Please note, Dettmers et al. (2001) did assess the presence of neuropathic pain, but do not report any pain intensities.