Magnetic resonance imaging assessment of degenerative cervical myelopathy: a review of structural changes and measurement techniques

Abstract

Degenerative cervical myelopathy encompasses a spectrum of age-related structural changes of the cervical spine that result in static and dynamic injury to the spinal cord and collectively represent the most common cause of myelopathy in adults. Although cervical myelopathy is determined clinically, the diagnosis requires confirmation via imaging, and MRI is the preferred modality. Because of the heterogeneity of the condition and evolution of MRI technology, multiple techniques have been developed over the years in an attempt to quantify the degree of baseline severity and potential for neurological recovery. In this review, these techniques are categorized anatomically into those that focus on bone, ligaments, discs, and the spinal cord. In addition, measurements for the cervical spine canal size and sagittal alignment are also described briefly. These tools have resulted collectively in the identification of numerous useful parameters. However, the development of multiple techniques for assessing the same feature, such as cord compression, has also resulted in a number of challenges, including introducing ambiguity in terms of which methods to use and hindering effective comparisons of analysis in the literature. In addition, newer techniques that use advanced MRI are emerging and providing exciting new tools for assessing the spinal cord in patients with degenerative cervical myelopathy.

Keywords: CR = compression ratio; CSA = cross-sectional area; DCM = degenerative cervical myelopathy; DTI = diffusion tensor imaging; FA = fractional anisotropy; IVD = intervertebral disc; JOA = Japanese Orthopaedic Association; LF = ligamentum flavum; MCC = maximum canal compromise; MRS = MR spectroscopy; MSCC = maximum spinal cord compression; MT = magnetization transfer; MTR = MT ratio; MWF = myelin water fraction; NAA = N-acetyl aspartate; OPLL = ossification of the posterior longitudinal ligament; PLL = posterior longitudinal ligament; ROI = region of interest; T1WI = T1-weighted imaging; T2WI = T2-weighted imaging; VB = vertebral body; cervical spondylotic myelopathy; compressive myelopathy; diffusion tensor imaging; disc disease; fMRI = functional MRI; mJOA = modified JOA; method; spine; stenosis.