A Novel Epidural Cauda Equina Compression Grading Scale for Metastatic Spine Disease: Does Severity of Compression Impact Outcomes

Introduction: While much is known about metastatic epidural spinal cord compression, less is known about metastatic epidural cauda equina compression. In patients undergoing metastatic spine surgery, we sought to classify cauda equina compression based on a novel scoring system to assess: 1) pre/postoperative neurologic function, 2) postoperative radiation patterns, and 3) long-term oncologic outcomes.

Methods: A retrospective, cohort study was undertaken of patients undergoing metastatic spine surgery for extradural, lumbar disease from 2010-21. The primary exposure variable was severity of epidural cauda equina compression based on the following novel scale: Grade-0=Bone only; Grade-1=Thecal sac indented but < 50% effaced; Grade-2=≥50% of thecal sac effaced; Grade-3= Entire thecal sac effaced with no (cerebrospinal fluid) CSF seen; Grade-4= Entire thecal sac effaced, no CSF, nerve root clumping above. An +F modifier was used for foraminal stenosis. Primary outcomes were neurologic function, type of radiation received, and local recurrence/survival. For analysis, the scoring system was dichotomized into partial compression (Grade 0-2) vs. complete compression (Grade 3-4). Descriptive and bivariate analyses were performed.

Results: Of 45 patients undergoing surgery for metastatic lumbar disease, 31 (69%) had complete (grade 3/4) cauda equina compression and 37 (82%) had the foraminal modifier. Four (13%) patients had cauda equina syndrome, and all had Grade 3/4 compression. Patients with Grade 3/4 compression had more biologic back pain (64.5% vs. 21.4%,p=0.007) but no difference in motor deficits (54.8% vs. 71.4%%,p=0.293) or urinary incontinence (19.4% vs. 14.3%, p=1.000). Patients with Grade 3/4 compression had significantly more estimated blood loss (1091 vs.368ml,p=0.001) and underwent SBRT much less frequently than Grade 1/2 compression (18.2% vs. 60.0%), though this was not statistically significant (p=0.245). Patients with Grade 3/4 compression had significantly lower postoperative KPS (p=0.015) but no difference in recurrence/survival.

Conclusion : Utilizing a novel metastatic epidural cauda equina compression scale, 69% patients had complete cauda equina compression (Grade 3/4) including all 4 (13%) presenting with cauda equina syndrome. SBRT was less common in patients with Grade 3/4 compression. The novel proposed scale warrants further study.