Introduction: Prior studies have shown neural degeneration rostral to the level of spinal cord compression in post-mortem evaluation of patients with cervical spondylotic myelopathy (CSM). However, conventional MRI rarely shows intramedullary changes rostral to the level of compression. Diffusion tensor imaging (DTI) has the potential to better elucidate structural changes in the spinal cord. The purpose of this study was to determine if patients with CSM had abnormal findings in the spinal cord at and rostral to the level of compression using DTI compared to normal controls.
Methods: 21 CSM patients (12 women, 9 men) and 20 neurologically intact controls underwent DTI of the cervical cord on a 1.5 T MR scanner. Baseline mJOA scores and Nurick grades were recorded. We measured DTI fractional anisotropy and longitudinal apparent diffusion coefficient at the level of compression and at C2-3 in CSM patients and compared this to controls using the Mann Whitney U test.
Results: The mean mJOA score was 13.8±0.4 and mean Nurick grade was 1.6±0.1. The majority of CSM patients had compression at C5-6 (47%) or C3-4 (23%). At C2-3, no compression or T2 abnormalities were noted. At C2-3 and the level of compression, fractional anisotropy was significantly lower among CSM patients vs normal controls (median 0.62 CSM vs 0.69 normal, p=0.005; 0.55 CSM vs 0.63 normal, p=0.004, respectively). The longitudinal apparent diffusion coefficient followed a similar pattern at C2-3.
Conclusions: In CSM, DTI shows abnormal findings both at and rostral to the level of compression compared to normal controls. Fractional anisotropy and longitudinal apparent diffusion coefficients are decreased at both levels compared to normals. These rostral DTI changes may reflect ascending neural degeneration from the level of compression and represent potential biomarkers for spinal cord dysfunction. Future work will evaluate the association between DTI metrics and patient clinical status and outcome.
Patient Care: Our research evaluates an imaging technique, DTI, that may better correlate with patient clinical status and outcome than conventional MRI imaging.
Learning Objectives: 1. Understand differences between conventional MRI and diffusion tensor imaging of the cervical spinal cord.
2. Recognize that DTI can detect abnormalities within the cervical cord rostral to the level of compression, even though conventional MRI imaging may not show abnormal signal changes.
3. Understand that DTI metrics may reflect ascending neural degeneration from the level of compression and represent potential biomarkers for spinal cord dysfunction.