Radiography
Findings
The lateral view of the spine is the most useful. Spondylosis appears as curvilinear bony outgrowths from the lateral and posterior margins of the vertebral body endplates. The general outline of each vertebral body should be reviewed to exclude possible compression injuries or pathologic compression fractures. Hypertrophic facet joints are best seen on oblique views in which narrowing of the neuroforaminal spaces in the cervical spine and lumbar spine regions are commonly visualized. In the cervical spine, uncovertebral hypertrophy is best visualized on oblique and lateral views. The AP view is useful for the assessment of alignment and uniformity of the interspinous process distances. The soft tissues surrounding the lumbar spine can be evaluated on the standard AP radiograph. Disruption of the psoas muscle stripe may indicate a paravertebral abscess or tumor.
Degree of Confidence
Standard radiographs remain the recommended initial imaging study of choice. In patients with severe stenosis, cervical spine radiographs are useful; however, radiographic studies are insensitive to soft-tissue hypertrophy and other nonosseous causes of spinal stenosis. In the older patient, standard radiographs help exclude more serious conditions, such as pathologic compression fracture. Anterior osteophytes, even when they become very large, may not be related to spinal symptoms.
False Positives/Negatives
While few false-positive findings exist, occasionally, even marked anterior spondylosis is not associated with significant central spinal canal narrowing. Diseases associated with bone softening may be related to significant spinal canal narrowing without obvious radiographic findings.
Computed Tomography
Findings
On CT scans, spinal stenosis is well defined as the diminished diameter(s) and cross-sectional area of the spinal canal. CT of the cervical spine can be improved using intravenous contrast agents to enhance the epidural veins, thus better defining the margins of the epidural space. Enhancement of epidural fibrosis is greatest soon after surgery. Paraspinal masses may present with associated calcifications or may appear as cystic or fluid collections in the case of abscess. In all cases the relationship of the mass to the central spinal canal, the lateral spinal canal recess, and the neuroforamen should be determined. All images should be reviewed with both a standard soft-tissue window and a narrow window to evaluate bone disease and calcifications.
Degree of Confidence
Osseous and calcified features are well outlined on CT scans. Findings in epidural soft-tissue diseases rely on the displacement of epidural fat or contrast enhancement, which may vary. In general, the use of intravenous contrast agents improves the visualization of soft tissue diseases, masses, and abscesses.
False Positives/Negatives
False-positive findings related to epidural scar result from a failure of fibrotic tissue to enhance years after surgery. False-negative CT examinations occur because of far lateral lesions, which become averaged together with the surrounding bone of the neuroforaminal space. The evaluation for an abscess is difficult immediately following surgery. The residual blood and gas in the tissues may appear similar to an infectious process. Delayed follow-up examinations are recommended.
Magnetic Resonance Imaging
Findings
On MRI, findings of spinal stenosis have a variable presentation depending on the specific disease causing the stenosis as well as associated edema of the related vertebral bodies.
- Osteophytes and calcified bulging disc structures are dark on T2-weighted fast spin-echo and T1-weighted spin-echo imaging.
- Osteophytic tissues are dark on T2-weighted gradient-echo images.
- Epidural soft tissues and related disease processes typically are isointense on T1-weighted noncontrast images, compared to muscle, synovial tissues, and most spinal ligaments.
- Vertebral endplates present a variable degree of increased or even decreased brightness on T2-weighted images, depending on the degree of inflammation and the chronic nature of the degenerative changes.
- Following intravenous administration of gadolinium diethylenetriamine pentaacetic acid (DTPA), fibrosis or surgical inflammatory changes, extra-axial tumors, and stress reactions within vertebral body endplates present an increased signal pattern on T1-weighted images.Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with troublemovingorstraightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
- Postcontrast T1-weighted images are most useful if a fat-suppression technique is used.
The assessment of cervical spine stenosis is improved by careful evaluation of CSF flow in the region of the stenosis. Spatial modulation of magnetization allows the degree of stenosis to be correlated with restriction to the CSF flow. In high-grade stenosis both the diastolic and the systolic CSF flow velocities are reduced. The degree of symptoms has been correlated to the compromised cervical cord and the related effects upon CSF flow.
Degree of Confidence
Spinal stenosis is best diagnosed using MRI. Measurements taken from sagittal images are particularly useful and, in most patients, can be accepted as accurate. Although measurement of the cervical canal are important, interpretation of the diagnosis of spinal canal stenosis must be made carefully. The clinical significance of spinal canal stenosis in children is probably less important than the increased mobility of the child's neck compared to that of the adult. Due to susceptibility artifacts related to osseous and calcified structures, gradient-echo images tend to result in slight overestimations of the degree of stenosis in the lateral recesses and neuroforaminal spaces.
False Positives/Negatives
On MRI, a false-positive finding of the spine rarely occurs except in patients with central spinal canal stenosis. Gradient-echo images may lead to overestimation of the degree of lateral recess and neuroforaminal space stenosis. CSF-pulsation artifacts seen on sagittal T2-weighted fast spin-echo images may give rise to a false impression of dorsal stenosis. False-negative MRI results are generally related to movement artifacts and the presence of metal in the region of interest.
Nuclear Imaging
Findings
Spinal stenosis may be reflected on SPECT nuclear medicine images as areas of increased activity related to the vertebral body endplates, facet joints, and uncovertebral joints. Medical diseases related to the bones of the vertebral bodies, such as Paget disease, present with markedly increased nuclide uptake. Metastatic disease, which may cause spinal canal stenosis, is usually associated with increased uptake of the nuclide agent in the areas of abnormal bone.
Degree of Confidence
Most causes of spinal stenosis have nonspecific findings on nuclear medicine studies. Paget disease, osteomyelitis, and spinal metastasis have strongly positive focal findings.
False Positives/Negatives
Many cases of spinal stenosis are not identified using SPECT nuclear medicine as a primary diagnostic method. Nuclear medicine scans may demonstrate positive findings in the absence of spinal stenosis. SPECT spinal imaging should be reserved for patients in whom osteomyelitis, Paget disease, or other specific disease conditions exist. Some diseases in which only bone destruction occurs may not have increased uptake in the areas of metastatic disease.
Angiography
Findings
Angiography is rarely indicated except in patients with arteriovenous malformations, dural fistulas, and vascular spinal tumors. In these patients, the degree of spinal canal narrowing can only be inferred on the basis of venous or arterial displacement or neovascularity.
Degree of Confidence
Spinal angiography can indicate spinal canal narrowing only indirectly, based on epidural enhancement and vascular (venous) dilatation.
False Positives/Negatives
Spinal angiography should be reserved for specific indications related to arteriovascular malformations, arteriovascular fistulae, and highly vascular tumors. Epidural venography was performed prior to the availability of MRI. As a result of the variability of the epidural venous plexus, use of epidural vein displacement as an indication of a lateral disc herniation is subject to both false-positive and false-negative diagnoses.
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 Imaging: Spinal Stenosis |
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Further Reading
Keywords
spondylosis
