Neuropathic pain and primary somatosensory cortex reorganization following spinal cord injury

Wrigley, P.J.; Press, S.R.; Gustin, S.M.; Macefield, V.G.; Gandevia, S.C.; Cousins, M.J.; Middleton, J.W.; Henderson, L.A.; Siddall, P.J.

doi:10.1016/j.pain.2008.10.007

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Volume 141, Issue 1 , Pages 52-59, January 2009

Neuropathic pain and primary somatosensory cortex reorganization following spinal cord injury

P.J. Wrigley
- Pain Management Research Institute, University of Sydney, Royal North Shore Hospital, St. Leonards 2065, Australia
S.R. Press
- Department of Anatomy and Histology, University of Sydney, Anderson Stuart Building, F13, Sydney, NSW 2006, Australia
S.M. Gustin
- Pain Management Research Institute, University of Sydney, Royal North Shore Hospital, St. Leonards 2065, Australia
- Department of Anatomy and Histology, University of Sydney, Anderson Stuart Building, F13, Sydney, NSW 2006, Australia
V.G. Macefield
- School of Medicine, University of Western Sydney, Sydney, NSW 1797, Australia
S.C. Gandevia
- Prince of Wales Medical Research Institute and the University of New South Wales, Sydney, NSW 2031, Australia
M.J. Cousins
- Pain Management Research Institute, University of Sydney, Royal North Shore Hospital, St. Leonards 2065, Australia
J.W. Middleton
- Rehabilitation Studies Unit, Faculty of Medicine, University of Sydney, Sydney, NSW 2065, Australia
L.A. Henderson
- Department of Anatomy and Histology, University of Sydney, Anderson Stuart Building, F13, Sydney, NSW 2006, Australia
- Corresponding author. Tel.: +61 2 9351 7063; fax: +61 2 9351 6556.
P.J. Siddall
- Pain Management Research Institute, University of Sydney, Royal North Shore Hospital, St. Leonards 2065, Australia

Received 6 April 2008; received in revised form 18 August 2008; accepted 14 October 2008. published online 25 November 2008.

Abstract

The most obvious impairments associated with spinal cord injury (SCI) are loss of sensation and motor control. However, many subjects with SCI also develop persistent neuropathic pain below the injury which is often severe, debilitating and refractory to treatment. The underlying mechanisms of persistent neuropathic SCI pain remain poorly understood. Reports in amputees describing phantom limb pain demonstrate a positive correlation between pain intensity and the amount of primary somatosensory cortex (S1) reorganization. Of note, this S1 reorganization has also been shown to reverse with pain reduction. It is unknown whether a similar association between S1 reorganization and pain intensity exists in subjects with SCI. The aim of this investigation was to determine whether the degree of S1 reorganization following SCI correlated with on-going neuropathic pain intensity. In 20 complete SCI subjects (10 with neuropathic pain, 10 without neuropathic pain) and 21 control subjects without SCI, the somatosensory cortex was mapped using functional magnetic resonance imaging during light brushing of the right little finger, thumb and lip. S1 reorganization was demonstrated in SCI subjects with the little finger activation point moving medially towards the S1 region that would normally innervate the legs. The amount of S1 reorganization in subjects with SCI significantly correlated with on-going pain intensity levels. This study provides evidence of a link between the degree of cortical reorganization and the intensity of persistent neuropathic pain following SCI. Strategies aimed at reversing somatosensory cortical reorganization may have therapeutic potential in central neuropathic pain.

Keywords: Chronic pain, S1 reorganization, Plasticity