Imaging Spinal Stenosis

Kiran S. Talekar, MD; Mougnyan Cox, MD; Elana Smith, MD; Adam E. Flanders, MD

Disclosures

Appl Radiol. 2017;46(1) 

In This Article

Imaging Modalities in Stenosis

Radiographs

Radiographs are often the initial means of evaluating back pain. Radiographs are low cost, readily available, and can assess for degenerative changes of disc height loss, vacuum phenomenon, osteophytes, and vertebral alignment (Figure 7). Unrelated causes of back pain, such as sacroiliac joint pathology, renal stones, or calcified aneurysmal dilatation of the aorta may also be identified. Soft tissue, disc and nerve evaluation are limited, and radiographs are insensitive for metastases and infection.[14]

Figure 7.

Lateral radiograph of the cervical spine demonstrates disc space narrowing and osteophytosis throughout the mid-lower cervical spine. There is degenerative listhesis at multiple levels. The soft tissue elements (discs, nerve roots, etc.) are not visualized.

Computed Tomography

Computed tomography is the best modality to depict bony anatomy for presurgical planning. It can also diagnose disc herniation and spinal stenosis and is superior to radiographs in detecting metastases and infection (Figures 8 and 9).[1,14] Nerve-root impingement is not reliably detected and has the added disadvantage of radiation exposure. Although typically performed without contrast, contrast-enhanced CT has been shown to provide improved visualization of disc pathology by evaluating for mass effect on the epidural venous plexus. Epidural enhancement surrounding a herniated disc can assist in its detection (Figure 10).[15]

Figure 8.

Sagittal retrospectively reconstructed image of the lumbar spine in bone windows with excellent depiction of bony anatomy, which may aid in surgical planning.

Figure 9.

Noncontrast retrospectively reconstructed sagittal CT image of lumbar spine demonstrates cortical and trabecular thickening of the L1 and L3 vertebral bodies in a patient with Paget's disease. CT is an excellent modality to evaluate for bony detail.

Figure 10.

Noncontrast (A) and contrast-enhanced (B) axial CT images of the cervical spine demonstrate how intravenous contrast may improve evaluation of the spinal canal and cord.

For patients unable to have an MRI or who have had an inconclusive MRI, CT myelogram can serve as an alternative. Although this is an invasive procedure, contrast in the subarachnoid space outlines the neural structures and is comparable to MRI in detecting stenosis and neural impingement (Figure 11).[1] CT myelogram is also useful in diagnosing CSF leak and nerve root avulsion.

Figure 11.

Sagittal retrospectively reconstructed CT myelogram image shows pannus formation at C1-C2 narrowing the thecal sac in a patient with rheumatoid arthritis (arrow).

Magnetic Resonance Imaging

Magnetic resonance imaging is the modality of choice to evaluate stenosis and disc pathology.[1,14] MRI has many advantages: it is noninvasive, has no ionizing radiation, has high sensitivity in diagnosing stenosis, has high soft tissue contrast, and it best depicts cord, nerve roots, and bone marrow abnormalities.[1,14] Standard MRI sequences in the lumbar spine may include sagittal T1-weighted, T2-weighted, STIR, and proton density-weighted, and axial T1- and T2-weighted sequences (Figures 12 and 13). In addition, contrast enhanced MRI may be necessary for indications such as infection, tumor, and post surgical evaluation. Note that T2-weighted GRE sequence, often used in cervical spine imaging, may overestimate stenosis and should be correlated with other sequences. MR images can also be degraded by susceptibility artifact from metallic hardware and may be contraindicated in some patients. In patients with history and physical examination findings consistent with degenerative lumbar spinal stenosis, MRI is suggested as the most appropriate, noninvasive test to confirm the presence of anatomic narrowing of the spinal canal or nerve root impingement.[1]

Figure 12.

Sagittal T1-weighted image of the lumbar spine. The lines in image A demonstrate the scan angle for axial images through the disc spaces. The lines in image B demonstrate standard angulation for axial stacked images.

Figure 13.

Standard sagittal sequences for noncontrast MRI. Marrow abnormalities are best assessed on T1-weighted and fat-suppressed T2-weighted images; disc abnormalities are best evaluated on T2-weighted and Short Tau Inversion Recovery images; and spinal cord and nerve roots are best assessed on sagittal and axial T2-weighted images. Level-by-level evaluation of degenerative change is best viewed on axial and sagittal T2-weighted images.

Dynamic flexion-extension radiographs (Figure 14) and CT and MRI with load bearing may also be performed as a useful adjunct.[1]

Figure 14.

Lateral radiographs of the cervical spine demonstrating normal atlanto-axial alignment in neutral position with dislocation on flexion (arrow).

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