Article Review 8

Author’s Name

Allan R. Martin, Nobuaki Tadokoro, Lindsay Tetreault, Elsa V. Arocho-Quinones, Matthew D. Budde, Shekar N. Kurpad, Michael G. Fehlings

Article Title

Imaging Evaluation of Degenerative Cervical Myelopathy: Current State of the Art and Future Directions (2018)

Journal Name

Neurosurgery Clinics of North America

1) Bibliography

Martin, A. R., Tadokoro, N., Tetreault, L., Arocho-Quinones, E. V., Budde, M. D., Kurpad, S. N., & Fehlings, M. G. (2018). Imaging Evaluation of Degenerative Cervical Myelopathy. Neurosurgery Clinics of North America, 29(1), 33-45. doi:10.1016/j.nec.2017.09.003

2) Purpose of the Article

The purpose of this article was to review each of the imaging modalities (plain radiography, CT and MRI) and describe their strengths, limitations, and clinical utility for the clinical uses, followed by a discussion of emerging spinal cord imaging techniques and their implications for the future of clinical management of degenerative cervical myelopathy (DCM).

3) Brief Description of Procedure and Findings/Results

This article summarizes the current imaging techniques:

i) Radiography provides versatile 2-D views of the spine that display several important features and can identify many sources of pathology. Radiography also offers excellent contrast between the vertebrae and surrounding structures. Plain films of the spine offer several advantages over other imaging techniques, because they can be taken with the patient and x-ray machine in almost any position, allowing assessment of spinal alignment and instability under physiologic conditions.

ii) CT can perform high-resolution cross-sectional imaging and provide 3-D views of the anatomy. Similar to radiographs, CT provides an excellent view of bony structures, albeit with the limitation that the subject is in the supine position. CT is widely available, fast (studies can usually be completed in under 10 minutes), and easy to access, allowing primary care physicians to order these investigations without long wait times. However, the view of soft tissues offered by CT is poor and not sufficient to identify spinal cord compression in individuals with suspected DCM.

iii) CT Myelography is an invasive technique in which contrast dye is injected into the lumbar cistern prior to CT imaging, providing excellent visualization of the contour of the spinal cord and potentially compressive surrounding structures. CT myelography, however, involves risks and is an uncomfortable or painful procedure, and in the current era it is rarely performed in patients who can undergo MRI.

iv) Various MRI sequences can produce images with T1-weighted, T2-weighted, and T2*-weighted contrast, each highlighting different anatomic and pathologic features. Furthermore, several methods of nulling specific tissues or regions are available, such as fat suppression with short-tau inversion recovery, which allows inspection of the spinal ligaments that tend to be surrounded by a small amount of fat. As a result, MRI provides noninvasive imaging of the spinal cord and surrounding tissues with unprecedented detail, playing a central role in clinical management of DCM.

v) A vast array of quantitative MRI (qMRI) techniques have become available that can measure specific physical properties of neural tissue, allowing characterization of microstructure and tissue injury with great implications for the management of DCM. The most popular of these techniques is diffusion tensor imaging (DTI), which can measure the directionality and magnitude of water diffusion. Magnetic resonance spectroscopy (MRS) is a technique that can characterize molecular and metabolic changes in the spinal cord, reflecting neuronal loss, gliosis, and demyelination. Finally, functional MRI (fMRI) provides information about the neural activity and connectivity in the spinal cord and associated brain structures.

4) Conclusions and Comments

i) For diagnosis purpose: Radiographs and CT can show the degree of bony canal stenosis, but they do not show the spinal cord and are thus not sufficient for diagnosis of DCM. MRI is the most useful imaging investigation for DCM diagnosis, because it clearly shows the outline of the spinal cord and nerve roots in relation to surrounding cerebrospinal fluid (CSF). T2-weighted images have the greatest contrast between cord and CSF, but T1-weighted or other image types may also show good contrast.

ii) For surgical purpose: The authors advocate that radiographs, CT, and MRI all provide useful information for surgical planning and should all be obtained, whenever possible, prior to surgical treatment of DCM.

iii) For most patients, MRI is sufficient for diagnosis, whereas radiographs, CT, and MRI are useful prior to and after surgery, although CT should be used sparingly in younger patients. In the near future, it can be expected that imaging (specifically MRI) will take on an even greater role in the management of DCM patients, including monitoring for progressive tissue injury, improved diagnosis, and outcome prediction.

5) The opinion of the Article

I thought this article was very easy to understand. It gave me a better understanding of how DCM is diagnosed and treated using different imaging modalities and current imaging techniques.