ABSTRACT
Study type: Reliability study
Introduction: Cervical spondylotic myelopathy (CSM) is the most common spinal cord disorder in
persons more than 55 years old. Despite multiple neuroimaging approaches proposed
to quantify the spinal cord compromise in CSM patients, magnetic resonance imaging
(MRI) remains the procedure of choice by providing helpful information for clinical
decision making, determining optimal subpopulations for treatment, and selecting the
optimal treatment strategies. However, the validity, reliability, and accuracy of
the MRI quantitative measurements have not yet been addressed.
Objective: To assess the intra- and inter-observer reliability of MRI quantitative measurements
of the spinal cord compromise in CSM patients.
Methods: Seventeen CSM patients (13-male) of mean age 54.5 years old were selected from the
AOSpine North America database. The patients had different combinations of stenotic
levels (1–4 levels) and the clinical severity (range mJOA baseline: 8–18). Asymptomatic
or previous surgically treated CSM, active infection, neoplastic disease, rheumatoid
arthritis, ankylosing spondylitis, trauma, or concomitant lumbar stenosis were excluded.
The patients underwent preoperative MRI using 1.5T (15 patients) and 3T (two patients)
scanner, including mid-sagittal T1-weighted, axial and mid-sagittal T2-weighted series.
MRI data were analyzed (Mango 2.0 software; Multi-Image Analysis GUI) by four blind
raters in three different sessions. Four measurements were analysed: transverse area
(TA) (Figure [1]), compression ratio (CR) (Figure [2]), maximal canal compromise (MCC), and maximal spinal cord compression (MSCC) (Figure [3]). The differences for each measurement were evaluated using mixed-effect ANOVA models
(ratter, session, ratter x session). The intra- and inter-rater reliability was evaluated
with intraclass correlation coefficients (ICC) (Figure [4]).
Results: The principal findings were: (i) for TA (71.48 ± 12.99mm2), the intra-rater agreement was 0.97 (95 % CI, range 0.94–0.99) and the inter-rater
agreement was 0.76 (95 % CI, range 0.49–0.90); (ii) for CR (0.35 ± 0.04 %), 0.94 (95 %
CI, range 0.88–0.98), and 0.79 (95 % CI, range 0.57–0.91) respectively; (iii) for
MCC (83.21 ± 2.08 %), 0.95 (95 % CI, range 0.89–0.98), and 0.64 (95 % CI, range 0.28–0.85)
respectively; and (iv) for MSCC (82.87 ± 1.52 %), 0.93 (95 % CI, range 0.86–0.97),
and 0.84 (95 % CI, range 0.65–0.93) respectively.
Conclusions: Our data suggest that three out of four measurements (TA, CR and MSCC) have acceptable
intra- and interreliability coefficients (ICC > 0.75). However, for the maximal canal
compromise measure, although the intrareliability was acceptable, the inter-rater
reliability was not acceptable (0.64). Based on this study, we recommend that three
MRI measures: transverse area, compression ratio and maximal spinal cord compression
should be used in the imaging assessment of the spinal cord in CSM patients.
