Schizas Grading of Lumbar Spinal Stenosis on MRI (A1–A4 / B / C / D) — free guideline decision tool

Grades central lumbar canal stenosis on axial T2 by the rootlet-to-CSF relationship in the dural sac: A (A1–A4) no or minor, B moderate, C severe, D extreme. No measurement needed; it reads in seconds and produces a report sentence.

Step 1: is CSF signal present in the dural sac? Yes → Step 2: do rootlets fill the whole sac? No → grade A, subtype by rootlet position: A1 (dorsal, <1/2), A2 (dorsal, horseshoe against dura), A3 (dorsal, >1/2), A4 (central, majority). Yes but still individualised → grade B. No → Step 3: is posterior epidural fat present? Present → grade C; absent → grade D. Use the axial T2-weighted image at disc level of the most stenotic segment. Look at CSF first, then whether rootlets can be separated, then dorsal epidural fat. Original study (Schizas 2010, n=95): intraobserver κ 0.65, interobserver κ 0.44. Weber 2015 and Lønne 2014 reported substantial interobserver agreement; Ko 2020 showed readers new to the system learned it readily.

Describing central canal stenosis in lumbar MRI reports, aligning terminology in clinic and pre-operative meetings, and comparing follow-up scans. Central canal only; lateral recess and foramina are graded separately.

A: no or minor stenosis; B: moderate; C: severe; D: extreme. In the original study C and D grades failed conservative care more often and A and B less often needed surgery, while grade did not relate to baseline ODI or surgical result. Mannion 2017 (157 surgical patients) found more severe stenosis predicted greater patient-rated benefit (grade D or DSCA <75 mm²: 4–13-fold odds of reaching MCIC); Weber 2016 (202 surgical patients) found no link between radiological severity and preoperative disability or 1-year outcome. The grade describes imaging; treatment follows symptoms, signs, and function.

Three looks: CSF, rootlet separability, posterior epidural fat. CSF present: A (not filling, A1–A4) or B (filling but separable). No CSF: C (posterior fat kept) or D (posterior fat gone). C/D fail conservative care more often, but grade is not a surgical indication.

Morphological grading does not replace clinical assessment, nor quantitative measures such as dural sac cross-sectional area; the two are complementary. Central canal only; describe lateral recess and foraminal stenosis separately. Grading relies on a single axial T2 slice; choose the narrowest level and check sagittal images. In the original study interobserver agreement was only moderate (mean κ = 0.44; intraobserver 0.65), so borderline cases may be reported as "between A4 and B". Imaging severity correlates inconsistently with symptoms and disability; do not decide surgery on grade alone. Diagrams on this page are hand-drawn schematics, not patient images; the original definitions prevail. For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.

Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.

Inputs: Level (optional, for the report sentence) L3/4, ① Is CSF (T2 bright signal) visible in the dural sac? Visible — CSF signal still present, ② Do the rootlets fill the whole dural sac? (answer if ① = visible) Not filling — CSF clearly visible, inhomogeneous distribution, ③ Grade A subtype: rootlet position (answer if ② = not filling) A2 — rootlets lie dorsally, in contact with the dura, horseshoe configuration, ④ Is posterior epidural fat still present? (answer if ① = not visible) Present — posterior epidural fat visible → Result: Grade · No or minor stenosis Schizas A2（Severity: No or minor stenosis, Definition: Rootlets lie dorsally, in contact with the dura but in a horseshoe configuration; CSF clearly visible but inhomogeneously distributed., Path: CSF visible → rootlets not filling → rootlet position） Inputs: Level (optional, for the report sentence) L1/2, ① Is CSF (T2 bright signal) visible in the dural sac? Visible — CSF signal still present, ② Do the rootlets fill the whole dural sac? (answer if ① = visible) Not filling — CSF clearly visible, inhomogeneous distribution, ③ Grade A subtype: rootlet position (answer if ② = not filling) A1 — rootlets lie dorsally, occupying less than half of the sac, ④ Is posterior epidural fat still present? (answer if ① = not visible) Present — posterior epidural fat visible → Result: Grade · No or minor stenosis Schizas A1（Severity: No or minor stenosis, Definition: Rootlets lie dorsally and occupy less than half of the dural sac area; CSF clearly visible but inhomogeneously distributed., Path: CSF visible → rootlets not filling → rootlet position）