Meng Law
Neck and back pain are very debilitating conditions that affect many in the normal aging process. Cervical spondylosis and myelopathy are difficult to treat because the therapeutic options include conservative management with pain medicine, physical therapy, and, in some cases, decompression surgery. The decision to consider surgery is currently dependent on the patient’s symptomatology, neurologic signs, and MRI findings, which include characterization of canal/foraminal stenosis and increased cord signal on T2-weighted imaging. The abnormal signal may indicate either early edema to late gliosis and cervical myelopathy. There is a wide spectrum of early transient signal change to irreversible spinal cord damage. Essentially, it is a challenge for neuroradiologists and spine surgeons to characterize this T2 signal change and understand what it means. One hypothesis behind the pathophysiology of this increased T2 signal is that venous/vascular compression of the epidural venous drainage in canal stenosis leads to venous back pressure into the spinal cord, and then edema. Further progression will lead to gliosis and myelopathy, which can sometimes be irreversible. In fact, many spine surgeons will tell you that at decompression the epidural veins are often engorged. Diffusion tensor imaging of the spine may have a role in the characterization of this spinal cord edema. It could potentially identify microscopic edema prior to seeing changes on T2WI. It may also be able to differentiate early edema from late degenerative myelopathy.1–4
In this paper, our initial goal was to determine if there are DTI changes within the cervical spinal cord in cervical degenerative disk disease. Our ultimate goal was to see if we could help the spine surgeon determine the most optimal timing for decompression surgery. We also had one other aim, which was to determine if some of these DTI changes are reversible following decompression surgery. However, our attempts to obtain high-quality DTI data with echo-planar imaging (EPI) sequences post surgery was hampered by susceptibility artifact and inhomogeneity from the implanted hardware/screws. Improvements with newer sequences may soon make this less of a challenge.