Magnetic resonance neurography in spinal cord injury: Imaging findings and clinical significance

Background and purpose: It is unknown whether changes to the peripheral nervous system following spinal cord injury (SCI) are relevant for functional recovery or the development of neuropathic pain below the level of injury. Magnetic resonance neurography (MRN) at 3 T allows detection and localization of structural and functional nerve damage. This study aimed to combine MRN and clinical assessments in individuals with chronic SCI and nondisabled controls.Methods: Twenty participants with chronic SCI and 20 controls matched for gender, age, and body mass index underwent MRN of the L5 dorsal root ganglia (DRG) and the sciatic nerve. DRG volume, sciatic nerve mean cross-sectional area (CSA), fascicular lesion load, and fractional anisotropy (FA), a marker for functional nerve integrity, were calculated. Results were correlated with clinical assessments and nerve conduction studies.Results: Sciatic nerve CSA and lesion load were higher (21.29 +/- 5.82 mm(2) vs. 14.08 +/- 4.62 mm(2), p < 0.001; and 8.70 +/- 7.47% vs. 3.60 +/- 2.45%, p < 0.001) in individuals with SCI compared to controls, whereas FA was lower (0.55 +/- 0.11 vs. 0.63 +/- 0.08, p = 0.022). DRG volumes were larger in individuals with SCI who suffered from neuropathic pain compared to those without neuropathic pain (223.7 +/- 53.08 mm3 vs. 159.7 +/- 55.66 mm3, p = 0.043). Sciatic MRN parameters correlated with electrophysiological results but did not correlate with the extent of myelopathy or clinical severity of SCI.Conclusions: Individuals with chronic SCI are subject to a decline of structural peripheral nerve integrity that may occur independently from the clinical severity of SCI. Larger volumes of DRG in SCI with neuropathic pain support existing evidence from animal studies on SCI-related neuropathic pain.