Magnetization Transfer Ratio and Morphometrics of the Spinal Cord Associates with Surgical Recovery in Patients with Degenerative Cervical Myelopathy

Abstract

Objectives: We assessed the prognostic value of the preoperative magnetization transfer ratio (MTR) and morphometrics of the spinal cord in patients with degenerative cervical myelopathy (DCM) in a longitudinal cohort study.

Methods: Thirteen subjects with DCM underwent 3T magnetization transfer imaging. The MTR was calculated for the spinal cord regions and specific white matter tracts. Morphometric measures were extracted. Clinical (modified Japanese Orthopaedics Association [mJOA] and Nurick scale scores) and health-related quality of life scores were assessed before and after cervical decompression surgery. The association between the magnetic resonance imaging (MRI) metrics and postoperative recovery was assessed (Spearman's correlation). Receiver operating characteristics were used to assess the accuracy of MRI metrics in identifying ≥50% recovery in function.

Results: Preoperative anterior cord MTRs were associated with recovery in mJOA scores (ρ = 0.608; P = 0.036; area under the curve [AUC], 0.66). Preoperative lateral cord MTR correlated with the neck disability index (ρ = 0.699; P = 0.011) and pain interference scale (ρ = 0.732; P = 0.007). Preoperative rubrospinal tract MTR was associated with mJOA score recovery (ρ = 0.573; P = 0.041; AUC, 0.86). Preoperative corticospinal tract and reticulospinal MTRs were related to recovery in pain interference scores (ρ = 0.591; P = 0.033; and ρ = 0.583; P = 0.035, respectively). Eccentricity of the cord was associated with Nurick scores (ρ = 0.606; P = 0.028) and mJOA scores (ρ = 0.651; P = 0.025; AUC, 0.92).

Conclusions: Preoperative MTR and eccentricity measurements of the spinal cord have prognostic value in assessing the response to surgery and recovery in patients with DCM. Advanced MRI and atlas-based postprocessing techniques can inform interventions and advance the healthcare received by patients with DCM.

Keywords: Degenerative spondylotic myelopathy; Magnetic resonance imaging; Prognostic utility; Spinal cord; Surgical outcomes.

Figure 1.

Illustration of magnetization transfer (MT) imaging: (A) without the MT pulse (MTC0), (B) with the MT pulse (MTC1), (C) MT Ratio (MTR), (D) region masks over the spinal cord, anterior cord (green), posterior cord (blue), and lateral cord (red).

Figure 2.

Functional recovery in patients with degenerative cervical myelopathy at 6 months after surgery: (A) Nurick score and (B) modified Japanese Orthopaedic Association (mJOA) score. Data reported as mean ± standard error.

Figure 3.

Association between anterior cord magnetization transfer ratio (MTR) and functional recovery rates: (A) modified Japanese Orthopaedic Association (mJOA) score and (B) pain interference scale (Pain-6a) score. Spearman’s ρ is reported.

Figure 4.

Association between lateral cord magnetization transfer ratio (MTR) and functional recovery rates: (A) pain interference scale (Pain-6a) score and (B) neck disability index (NDI). Spearman’s ρ is reported.

Figure 5.

Association between white matter tract magnetization transfer ratio (MTR) and functional recovery rates: (A) rubrospinal MTR related to modified Japanese Orthopaedic Association (mJOA) score and (B) corticospinal MTR related to pain interference scale (Pain-6a) score. Spearman’s ρ is reported.

Figure 6.

Association between cord eccentricity and functional recovery rate. (A) Eccentricity related to modified Japanese Orthopaedic Association (mJOA) score. Spearman’s ρ is reported. (B) Receiver operating characteristic (ROC) curve denoting accuracy of eccentricity in identifying ≥50% mJOA recovery. Area under the curve is reported.