The epidural spinal cord compression (ESCC) scale, sometimes known eponymously as the Bilsky scale, is used to assess the degree to which vertebral body metastasis compromises the spinal canal and whether cord compression is present. It may serve as a guide as to when intervention (radiotherapy or surgery) is helpful.

It is sometimes used in conjunction with the complementary CT-based spinal instability neoplastic score (SINS).

Radiographic features

The system uses axial T2-weighted images at the most severe spinal canal compromise site.

Classification

The scale is nominally a 4-point scale, but grade 1 is further subdivided into 1a, 1b and 1c, making it a 6-point scale in practice ¹. Increasing grades denote increasing degrees of stenosis:

• grade 0: bone-only disease

• grade 1: epidural extension without cord compression

  • 1a: epidural extension only (no deformation of the thecal sac)

  • 1b: deformation of the thecal sac, without spinal cord abutment

  • 1c: deformation of the thecal sac, with spinal cord abutment

• grade 2: spinal cord compression, with cerebrospinal fluid (CSF) visible around the cord

• grade 3: spinal cord compression, no CSF visible around the cord

History and etymology

The scale was proposed in 2010 by American neurosurgeon Mark Bilsky (fl. 2024) ³.

Practical points

• in the absence of mechanical instability, grades 0, 1a, and 1b are considered "low-grade" with radiation as initial treatment ⁴

• the role of surgery and radiosurgery in patients with grade 1c epidural is controversial (c.2022) ⁴, with high-dose hypofractionated radiation as a possible SRS option ²

• grades 2 and 3 represent "high-grade" epidural spinal cord compression and require surgical decompression before radiation therapy unless the tumour is highly radiosensitive ⁴