Increased Spinal Cord Stiffness with Extramedullary Compression, Quantitative Evaluation Using Intraoperative Ultrasound Elastography, and Development of Elasticity Index

Introduction: Recent quantitative evaluation of the spinal cord elasticity (SCE) using intraoperative shear wave ultrasound elastography(SWE) demonstrated increased spinal cord stiffness when it is compressed. However, more data is needed to further define the SCE features and its influencing factors. In the current study, we aimed to evaluate the changes in human SCE before and after tumor resection using intraoperative SWE.

Methods: A prospective study including all consecutive patients with spinal cord (SC) compression secondary to extramedullary-intradural tumors from January 2021 to September 2024. SCE was evaluated using intraoperative SWE before and after tumor removal in 3 areas; the area of maximum SC compression(zone 1), the SC with reduced diameter immediately adjacent to the tumor(zone 2), and the SC with a normal diameter distally(zone 3). An average of three measurements for each area was recorded. The tumor elasticity was evaluated. The elasticity index was calculated as the ratio of maximum compression to normal diameter. Paired t-tests were used to compare pre- and post-resection measurements.

Results: 23 patients (16 females, 7 males) were included, with 69.6% of tumors located in the thoracic region. The SC exhibited higher elasticity values in the compressed state, there was a significant difference between the SCE at zone 1 and zone 3 from above and below(p-value=0.001). The SCE at zone1 decreased significantly from 38.8kpa to 10.66kpa post-resection(p < 0.05). SCE in zone 3 and above the tumor decreased from 18.7kpa to 10.7kpa(p=0.063), and below the tumor from 25.97kpa to 12.09kpa(p=0.003). Comparing pre and post tumor resection, the elasticity index above the tumor decreased significantly from 2.77 to 0.93(p=0.016), and below the tumor from 2.46 to 0.76(p=0.040).

Conclusion : Intraoperative SWE ultrasound demonstrated a significant reduction in SCE following tumor resection. These findings suggest that this technique can effectively quantify changes in SCE, providing valuable insights into the biomechanical effects of spinal cord decompression.