Neuroimaging of Spinal Canal Stenosis

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Key points

  • Spinal stenosis is a broad term encompassing central, lateral, and foraminal narrowing and implies compromise of the neural structures passing through that space.

  • Imaging of spinal stenosis is primarily with MR imaging; however, CT and CT myelography (CTM) are acceptable alternatives.

  • There is often a mismatch between imaging and clinical findings; accurate and rigorous interpretation of the imaging is necessary for correct management decisions.

  • Cross-sectional imaging is usually acquired in a

Lumbar spinal stenosis

The North American Spine Society 2011 revised guidelines1 provide the following definition:

Degenerative lumbar spinal stenosis describes a condition in which there is diminished space available for the neural and vascular elements in the lumbar spine secondary to degenerative changes in the spinal canal. When symptomatic, this causes a variable clinical syndrome of gluteal and/or lower extremity pain and/or fatigue, which may occur with or without back pain. Symptomatic lumbar spinal stenosis

Natural history

There is a conspicuous absence of good-quality longitudinal studies documenting the natural history of patients with symptomatic lumbar canal stenosis. The North American Spine Society issued a statement that in the absence of reliable evidence, it is likely that the natural history of patients with mild to moderate symptomatic degenerative stenosis is favorable in one-third to one-half of patients. In patients with mild to moderate symptomatic stenosis, rapid or catastrophic neurologic decline

Clinical presentation of lumbar spinal stenosis

The diagnosis of lumbar spinal stenosis may be considered in older patients presenting with a history of gluteal or lower extremity symptoms exacerbated by walking or standing which improves or resolves with sitting or bending forward. Patients whose pain is not made worse with walking have a low likelihood of stenosis.1

There may be relative relief of symptoms on walking up an incline due to flexion of the lower spine. Saddle anesthesia and bladder disturbance are present in approximately 10%

Dynamic imaging

Imaging of the spine is routinely performed with the patient supine and in as relaxed a state as possible. The symptoms of spinal stenosis are commonly exacerbated by standing, walking, and extension. Imaging in extension versus neutral versus flexion and in an upright position or with axial loading applied have all been investigated to assess the relative effects on the spinal canal. Multiple studies have demonstrated a reduction in both dural sac area and midsagittal diameter on extension.

Cervical stenosis

Cervical spondylosis is a common finding that increases with age. Degeneration of nucleus pulposus of the intervertebral disk leads to narrowing of the disk space, bulging of the annulus fibrosis, buckling of the ligamentum flavum, disk-osteophyte bar formation, and hypertrophic osteoarthritic changes of the facet and uncovertebral joints. This cascade of degenerative processes may or may not result in cervical stenosis. As in the lumbar canal, cervical stenosis may refer to central, lateral,

Thoracic spinal stenosis

Degenerative thoracic stenosis occurs much less commonly than cervical or lumbar stenosis; this is likely due to the structural support of the rib cage and the relative reduced movement. When it does occur, it is most frequently seen in the lower thoracic levels (T8–T12), possibly because of greater movement. The clinical presentation is that of myelopathy and/or radiculopathy and relates specifically to the level of the pathology. Disk-osteophyte bars and facet joint and ligamentum flavum

Summary

MR imaging is first-line investigation of spinal stenosis. The site, extent, and number of stenotic lesions may be demonstrated with great resolution and clarity. Standard MR imaging sequences are unable, however, to visualize the dynamic changes that occur in the spine on loading and movement. Furthermore, they are largely unable to detect the subtle histopathologic changes that occur as a result of compression, repetitive strain, venous congestion, ischemia, and inflammatory processes.

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      Literature is full of different recommendation studies. In 2016, Cowley9 published a review analyzing the circumstances underlying the physical narrowing of the spinal canal, the pathophysiology of clinical syndromes associated with stenosis, the assessment of the strengths and weaknesses of different imaging strategies, the different observational sings and objective criteria that have been proposed in neuroimaging literature, and clinical-radiologic correlation. Andreisek et al10 presented the results of a consensus conference regarding core radiologic parameters to describe the lumbar stenosis.

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    The author has nothing to disclose.

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