Abstract
IntroductionWhile numerous studies have documented evidence for plasticity of the human brain there is little evidence that the human spinal cord can change after injury. Here, we employ a novel spinal fMRI design where we stimulate normal and abnormal sensory dermatomes in persons with traumatic spinal cord injury and perform a connectivity analysis to understand how spinal networks process information.MethodsSpinal fMRI data was collected at 3 Tesla at two institutions from 38 individuals using the standard SEEP functional MR imaging techniques. Thermal stimulation was applied to four dermatomes in an interleaved timing pattern during each fMRI acquisition. SCI patients were stimulated in dermatomes both above (normal sensation) and below the level of their injury. Sub-group analysis was performed on healthy controls (n = 20), complete SCI (n = 3), incomplete SCI (n = 9) and SCI patients who recovered full function (n = 6).ResultsPatients with chronic incomplete SCI, when stimulated in a dermatome of normal sensation, showed an increased number of active voxels relative to controls (p = 0.025). There was an inverse relationship between the degree of sensory impairment and the number of active voxels in the region of the spinal cord corresponding to that dermatome of abnormal sensation (R2 = 0.93, p<0.001). Lastly, a connectivity analysis demonstrated a significantly increased number of intraspinal connections in incomplete SCI patients relative to controls suggesting altered processing of afferent sensory signals.ConclusionsIn this work we demonstrate the use of spinal fMRI to investigate changes in spinal processing of somatosensory information in the human spinal cord. We provide evidence for plasticity of the human spinal cord after traumatic injury based on an increase in the average number of active voxels in dermatomes of normal sensation in chronic SCI patients and an increased number of intraspinal connections in incomplete SCI patients relative to healthy controls.
Highlights
While numerous studies have documented evidence for plasticity of the human brain there is little evidence that the human spinal cord can change after injury
The effect of traumatic injury to the spinal cord is classically considered in two stages, the primary injury, whereby mechanical forces are transmitted through the spinal column resulting in a shear force to axons and blood vessels within the spinal cord and the secondary injury that encompasses a cascade of events whereby the remaining viable neural tissue responds to its new, damaged environment.[1]
In this study we compared 20 healthy individuals with 18 chronic traumatic spinal cord injury patients who sustained their injury at least 12 months prior to enrolling in our study
Summary
While numerous studies have documented evidence for plasticity of the human brain there is little evidence that the human spinal cord can change after injury. We employ a novel spinal fMRI design where we stimulate normal and abnormal sensory dermatomes in persons with traumatic spinal cord injury and perform a connectivity analysis to understand how spinal networks process information. Traumatic spinal cord injury (SCI) results in an acute disruption of afferent somatosensory signals and an inability to process motor, autonomic and reflex arcs within the damaged region of the spinal cord. This interplay between ongoing destructive mechanisms and innate reparative processes eventually reaches a balance that is often described in terms of adaptive or maladaptive plasticity
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