Diagnostic Accuracy of CT for Metastatic Epidural Spinal Cord Compression

Abstract

Background: Early diagnosis of metastatic epidural spinal cord compression (MESCC) is vital to expedite therapy and prevent paralysis. Staging CT is performed routinely in cancer patients and presents an opportunity for earlier diagnosis.

Methods: This retrospective study included 123 CT scans from 101 patients who underwent spine MRI within 30 days, excluding 549 CT scans from 216 patients due to CT performed post-MRI, non-contrast CT, or a gap greater than 30 days between modalities. Reference standard MESCC gradings on CT were provided in consensus via two spine radiologists (11 and 7 years of experience) analyzing the MRI scans. CT scans were labeled using the original reports and by three radiologists (3, 13, and 14 years of experience) using dedicated CT windowing.

Results: For normal/none versus low/high-grade MESCC per CT scan, all radiologists demonstrated almost perfect agreement with kappa values ranging from 0.866 (95% CI 0.787-0.945) to 0.947 (95% CI 0.899-0.995), compared to slight agreement for the reports (kappa = 0.095, 95%CI -0.098-0.287). Radiologists also showed high sensitivities ranging from 91.51 (95% CI 84.49-96.04) to 98.11 (95% CI 93.35-99.77), compared to 44.34 (95% CI 34.69-54.31) for the reports.

Conclusion: Dedicated radiologist review for MESCC on CT showed high interobserver agreement and sensitivity compared to the current standard of care.

Keywords: Bilsky classification; CT; MRI; computed tomography; epidural spinal cord compression; magnetic resonance imaging; metastatic epidural spinal cord compression; metastatic spinal cord compression; spinal metastases classification; spinal metastatic disease; spine oncology study group.

Figure 1

Bilsky grading for metastatic epidural spinal cord compression (MESCC) was demonstrated using axial CT, MRI (T2-weighted), and a picture for each grade (right to left). The red shaded region shows MESCC in each image. Grade 0/normal (Black outline): No metastatic epidural disease present. Low-grade MESCC (Blue outline); Grade 1a: Metastatic epidural soft tissue with no thecal sac deformity, or Grade 1b: Metastatic epidural soft tissue with thecal sac deformity but no spinal cord contact. High-grade MESCC (Red outline); Grade 1c: Metastatic epidural soft tissue touching the spinal cord with no discernible compression or displacement, or Grade 2: Metastatic epidural soft tissue cord compression with some surrounding cerebrospinal fluid still visible, or Grade 3: Metastatic epidural spinal cord compression without discernible surrounding cerebrospinal fluid. Thecal sac = black outline within the spinal canal, Spinal cord = Yellow shaded area within the spinal canal.

Figure 2

Flow chart demonstrating the overall study design with inclusions and exclusions highlighted. MESCC = Metastatic epidural spinal cord compression.

Figure 3

Subtle low-grade metastatic epidural disease at the left anterolateral spinal canal at T6. This was undercalled by all three radiologists and is challenging due to the paucity of bony change and location at the typical site for an epidural vein.

Figure 4

Axial CT image of the cervicothoracic junction overcalled as low-grade epidural disease by two radiologists. No epidural disease was present on the corresponding MRI (not shown). Assessment is complex due to overlap and angulation of the lower cervical and upper thoracic spine in the axial plane with background degenerative changes.