Tissue bridges predict neuropathic pain emergence after spinal cord injury

Objective To assess associations between preserved spinal cord tissue quantified by the width of ventral and dorsal tissue bridges and neuropathic pain development after spinal cord injury. Methods This retrospective longitudinal study includes 44 patients (35 men; mean (SD) age, 50.05 (18.88) years) with subacute (ie, 1 month) spinal cord injury (25 patients with neuropathic pain, 19 pain-free patients) and neuroimaging data who had a follow-up clinical assessment at 12 months. Widths of tissue bridges were calculated from midsagittal T2-weighted images and compared across groups. Regression analyses were used to identify relationships between these neuroimaging measures and previously assessed pain intensity and pin-prick score. Results Pin-prick score of the 25 patients with neuropathic pain increased from 1 to 12 months (Delta mean=10.08, 95% CI 2.66 to 17.50, p=0.010), while it stayed similar in pain-free patients (Delta mean=2.74, 95% CI -7.36 to 12.84, p=0.576). They also had larger ventral tissue bridges (Delta median=0.80, 95% CI 0.20 to 1.71, p=0.008) at 1 month when compared with pain-free patients. Conditional inference tree analysis revealed that ventral tissue bridges' width (<= 2.1 or >2.1 mm) at 1 month is the strongest predictor for 12 months neuropathic pain intensity (1.90 +/- 2.26 and 3.83 +/- 1.19, p=0.042) and 12 months pin-prick score (63.84 +/- 28.26 and 92.67 +/- 19.43, p=0.025). Interpretation Larger width of ventral tissue bridges-a proxy for spinothalamic tract function-at 1 month post-spinal cord injury is associated with the emergence and maintenance of neuropathic pain and increased pin-prick sensation. Spared ventral tissue bridges could serve as neuroimaging biomarkers of neuropathic pain and might be used for prediction and monitoring of pain outcomes and stratification of patients in interventional trials.