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Objectives and questions: Traumatic spinal cord injury (tSCI) is caused by mechanical tissue destruction and is followed by progressive secondary injury expansion characterized by hemodynamic disruption and chronic tissue loss. Although extensive research has aimed to develop experimental neuroprotective strategies to halt secondary injury and preserve functional spinal cord tissue, little is known about the region-specific spatial characteristics of injury expansion (i.e., cervical versus thoracic).

Material and methods: Here, we prospectively used contrast-enhanced ultrasound imaging (CEUS) to track the subacute progression (3 days post-injury) of cervical or thoracic contusion tSCI in a well-validated rodent model. Longitudinal midline CEUS imaging was performed before, immediately after, and 3 days post injury in 11 Long-Evans rats (n = 6 thoracic, n = 5 cervical respectively). The primary aim was a characterization of the longitudinal spatiotemporal injury expansion. Paired t-tests were used to determine statistical significance (α=0.05).

Results: Volumetric analysis revealed that the rostrocaudal expansion of the ischemic perfusion deficit was nearly symmetric in cervical tSCI (57.7±7.06% of total expansion rostrally), whereas in thoracic tSCI the expansion was almost entirely directed caudally (97.9±1.73% of total expansion). Using ultrasound localization microscopy, we observed striking differences in the orientation of the central sulcal arteries (cervical: oriented caudally at an angle of 24.0±4.84°; thoracic: oriented rostrally at an angle of –30.5±3.81°) (Figure 1). We speculate that the differing orientations of these intrinsic vessels may mechanically shape the expansion of the necrotic injury core. Dynamic CEUS measurements of relative blood volume revealed asymmetric hyperemia in the gray matter rostral to thoracic tSCI only (1.53±0.22-fold relative to baseline), while both cervical and thoracic injuries exhibited hyperemia in the white matter rostral to the lesion (cervical: 1.79±0.24-fold; thoracic: 2.00±0.31-fold).

Discussion and conclusions: To our knowledge, this is the work to reveal region-specific differences in injury expansion following tSCI, highlighting the potential for personalized spinal cord region-specific neuroprotective interventions in future work.