MRI in chronic spinal cord injury patients with and without central pain

Background: Central pain following spinal cord injury (SCI) is common and thought to be related to lesion of the spinothalamic pathways. Objective: To examine additional mechanisms of SCI pain. Methods: Twenty-three SCI patients with traumatic lesions above T10 ( 14 with central neuropathic pain and 9 without pain) underwent MRI examination. The authors quantitatively assessed extent of cord lesion on axial T2-weighted images as percentage of 1) gray matter, 2) dorsolateral, 3) anterolateral, and 4) dorsolateral columns based on standardized drawings made by a neuroradiologist blinded to patient history. Results: At the level of maximal cord injury, 21 patients had lesions involving the entire cord on axial images except for a small border of lower signal intensity, whereas 2 patients had central lesions. Rostral to the main injury, the first image with an incomplete lesion showed significantly more involvement of gray matter in pain than in pain-free patients. Conclusion: Consistent with animal models of SCI, spinothalamic tract lesion together with neuronal hyperexcitability due to lesion of inhibitory interneurons at the rostral end of injury are hypothesized to lead to central pain.