Neuropathic Pain Linked to Decreased Motor Cortical Plasticity After Spinal Cord Injury

Researchers uncover new data on brain reorganization after spinal cord injury.

A research team led by Catherine R. Jutzeler, PhD, from the Spinal Cord Injury Center at the University of Zurich, has uncovered new information about the dynamic potential of the brain to reorganize following spinal cord injury (SCI).

Investigators found that the intensity of neuropathic pain in those with SCI was negatively correlated with motor cortical remapping. Published in the December issue of Journal of Pain,1 the findings provide evidence that reorganization in the primary motor cortex after spinal cord injury is limited to individuals without neuropathic pain.

Neuropathic pain not linked to increased plasticity

The study population was comprised of 24 individuals with sensorimotor complete and incomplete paraplegia and tetraplegia; 31 healthy individuals served as controls. Functional magnetic resonance imaging (fMRI) was used to measure cortical activation in response to 4 sensory and motor tasks.

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Tasks included brushing performed at the C6 dermatome at the base of the thumb; the application of heat packs to the C6 dermatome; passive wrist extension in which the wrist was extended and brought back to its starting position using a strap; and active wrist extension in which the participant was asked to extend their wrist and then return to the starting position.

Results showed that task-evoked patterns of brain activation did not differ between SCI patients and controls. However, significant differences were observed in the location of peak activation.

In the SCI group, topographical shifts in peak activity took place in sensory and motor cortices after sensory stimulation or active movement. Patients with SCI and neuropathic pain demonstrated larger topographical shifts in the primary motor cortex that correlated negatively with pain intensity, such that patients with higher intensity of neuropathic pain more resembled healthy controls than pain-free individuals with SCI.

The findings indicate that neuropathic pain in motor and sensory tasks at or above the level of the lesion is not associated with increased plasticity.

“In addition to demonstrating reorganization after SCI, these novel findings indicate that [neuropathic pain] may preserve functional cortical topography,” the authors note.