Cervical extension magnetic resonance imaging in evaluating cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) may be caused by static and dynamic spinal cord compression, particularly during neck extension. Dynamic compression may be better evaluated with dynamic magnetic resonance (MR) images. We performed a retrospective study to determine the clinical indication for dynamic MR imaging, and conducted a survey regarding image interpretation by clinicians.

A total of 32 patients (M:F = 20:12, 60.1 ± 10.7 years) who had undergone neutral/extension cervical MR imaging were included. The study population consisted of 22 patients with signs of cervical myelopathy (M group) and 10 patients without signs of myelopathy (NM group). The number of compression levels (complete obliteration of the anterior and posterior subarachnoid space) was assessed at each level in mid-sagittal, T2-weighted, neutral and extension MR images. Reproduced images from 22 patients in the M group were randomly arranged, and four experienced spine surgeons at four different institutes interpreted them to reach a clinicians' agreement. The agreements were then assessed with inter-rater correlation coefficients (ICC).

Analysis with extension MR images found an increased number of compression levels in 23/32 (72 %) of patients; 20/22 in the M group and 3/10 in the NM group (p < 0.01, chi-squared test), as compared to findings of the neutral MR images. Clinical factors for increased compression levels in extension MR images were age (p < 0.01, 63.3 ± 10.0 years vs. 51.9 ± 8.1) and signs of myelopathy (p < 0.01, odds ratio, 23.33). Clinician agreement was improved with extension MR images; ICC was 0.67 with neutral and 0.81 with extension MR images.

The evaluation of CSM may be improved with dynamic MR images. Dynamic MR scanning may be considered for elderly patients with signs of myelopathy, but an interpretation for asymptomatic spinal compression based exclusively on extension MR image should be made with caution.