Article Review 5

Author’s Name

Linda I. Suleiman, Surabhi A. Bhatt, Todd B. Parrish, and Alpesh A. Patel

Article Title

Imaging Modalities and Tests for Cervical Myelopathy (2014)

Journal Name

Seminars in Spine Surgery

1) Bibliography

Suleiman, L. I., Bhatt, S. A., Parrish, T. B., & Patel, A. A. (2014). Imaging modalities and tests for cervical myelopathy. Seminars in Spine Surgery, 26(2), 68-72. doi:10.1053/j.semss.2014.05.003

2) Purpose of the Article

The purpose of this article was to summarize the current techniques that are routinely used in the diagnosis of cervical spondylotic myelopathy (CSM) – plain X-ray radiographs, MRI, and CT/CT myelography; as well as discuss two innovative MRI techniques – magnetization transfer (MT) MRI and diffusion tensor imaging (DTI).

3) Brief Description of Procedure and Findings/Results

This article told that several dynamic factors play a key role in the pathophysiology of CSM. These dynamic factors may be associated with changes to the cross-sectional area, spinal cord diameter and subarachnoid space that are unique to the cervical spine.

i) Radiography/plain films remain an integral part of the initial workup and evaluation of stability of the cervical spine. Static plain films such as an anteroposterior (AP), lateral and dynamic films such as flexion and extension should be obtained. Most surgeons advocate obtaining flexion and extension views to determine segmental instability and alignment. These films not only evaluate basic age-related changes such as disk space narrowing and osteophytic changes but also help with preoperative surgical planning. Several alignment parameters, including Cobb angle and C2 plumb line, have been reported in the assessment of CSM patients. Alignment may be involved with disease pathophysiology, can drive surgical decision making, and may correlate to patient outcomes. Recently cervical kyphosis has been associated with myelopathy due to an applied force on the spinal cord against the vertebral bodies and thus increasing the longitudinal cord tension.

ii) MRI is sensitive to multiple imaging parameters that allow high-resolution imaging that can generate a myelographic image, facet joint and nerve root images, or images that reflect the internal structures of the spinal cord. These different imaging sequences all the detection of the severity of degenerative changes, the degree of cord compression and incidence of intrinsic spinal cord abnormalities. MRI is the best imaging modality to evaluate not only intramedullary lesions but also cord compromise. The largest disadvantage of MRI is, in isolation, its lack of clinical utility for degenerative spinal conditions. MRI does not allow physicians to predict patient symptoms and function, anticipate clinical deterioration, or guide decision making without clinical correlation from the history and physical examination. There are also limitations on the quality of images secondary to section thickness, signal-to-noise problem and cerebrospinal fluid motion; however, using modern scanner hardware and proper protocols can address these limitations.

iii) CT/CT Myelography - CT has remained superior to MRI when evaluating bony parameters. CT myelography to be far superior as a measure of spinal stenosis and bony lesions. CT myelography involves placing radiopaque dye into the spinal cord followed by a CT in order to evaluate stenosis. Many studies have compared CT myelography to MRI in the evaluation of CSM and concluded that CT myelogram provides complementary results to MRI. Some surgeons will use a CT myelogram to provide additional information regarding foramina stenosis caused by bony outgrowth and to better quantify the degree of compression.

iv) Diffusion tensor imaging (DTI) identifies alterations in the white matter tract and allows us to quantify these changes using parameters such as fractional anisotropy (FA) and the apparent diffusion coefficient (ADC). DTI uses magnetic field gradients in multiple directions to measure the diffusion characteristics of water. If the cord is compressed, there is a restriction of water diffusion and intramedullary oedema. DTI could explain more specific clinical symptoms found in myelopathic individuals by quantifying changes over time in the white matter of the spinal cord. Although DTI can help quantify spinal cord lesions, the actual resolution and image quality of DTI of the spinal cord is inferior to the image quality of the brain considering there are higher demands in spatial resolution. Additional challenges to DTI include dynamic events around the cord such as the carotid and aortic pulsations, respiratory movements, swallowing and CSF pulsations can result in artifact. There is also the issue of magnetic susceptibility around all the vertebral bone that can cause signal loss and distortion. Lastly, large-scale validation of DTI as both diagnostic and prognostic in the evaluation of CSM has yet to be reported.

v) Magnetization transfer (MT) is a technique for generating image contrast in MRI based on the application of off-resonance radio-frequency pulses and observing their effects on MR images. MT permit the noninvasive evaluation of the functional and physiologic properties of the spinal cord. MT has been previously utilized in the study of multiple sclerosis to identify clinically relevant differences in lesion severity beyond what could be detected by conventional MRI. MT images demonstrate less signal-to-noise and greater resolution of myelin degeneration within the substance of the spinal cord. MT MRI has the potential to improve upon conventional MRI imaging by providing information about tissue microstructure and may be particularly well suited for assessing the integrity of fibre tracts in SCI.

4) Conclusions and Comments

Radiologic evaluation, including both existing (Plain x-ray, CT and MRI) and emerging techniques (DTI and MT MRI), in addition to a detailed history and physical examination will define optimal treatment strategies for CSM. Advanced magnetic resonance approaches like DTI and MT had significantly improved the diagnostic accuracy of CSM. 

5) The opinion of the Article

I thought this article was very easy to understand. It gave me a better understanding of how CSM is diagnosed and treated using different imaging modalities, including both existing and emerging techniques.