Degenerative lumbosacral stenosis in dogs - Veterinary Medicine
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Degenerative lumbosacral stenosis in dogs
You may not readily recognize degenerative lumbosacral disease in your large-breed patients because they commonly have other concurrent orthopedic diseases. Here's how to identify affected dogs and help them with the right therapy.


Computed tomography

Figure 10: A sagittal plane computer reconstruction of a CT image of the lumbosacral articulation in a dog. Image A represents the plane of the reconstructed image. Image B is the sagittal reconstruction. Note the herniated intervertebral disk (cranial is to the left side of Image B); Figure 11: A sagittal plane MRI of the lumbosacral vertebral column in a dog. The top image is T2-weighted, and the bottom image is T1-weighted. A large herniation of the L7-sacral intervertebral disk is present. In the bottom left inset, the intervertebral disk herniation (arrow), ventral spondylosis (arrowhead), and sacrum (asterisk) are identified.
CT has largely replaced plain radiography for evaluating patients suspected of having degenerative lumbosacral stenosis. CT provides a cross-sectional evaluation of the complex anatomy and has better soft tissue resolution compared with plain radiography, thereby allowing better assessment of the diameter of the vertebral canal, articular processes, intervertebral disk, lateral recesses, and nerve roots. Abnormalities identified with CT include intervertebral disk herniation and consequent loss of epidural fat, narrowing of the intervertebral foramen, abnormalities in the articular processes, and spondylosis (Figures 9 & 10).30 Adding intravenous iodinated contrast media may enhance visualization of the anatomy of the lumbosacral articulation.31 Unfortunately, as with all other imaging modalities, the magnitude of abnormalities identified with CT does not correlate with clinical signs.32 In fact, lumbosacral stenosis has been identified in dogs without clinical signs.33

Magnetic resonance imaging

MRI has largely replaced other diagnostic imaging techniques as the premier imaging modality for evaluating the nervous system. As with CT, MRI provides cross-sectional images of the complex anatomy of the lumbosacral articulation. Furthermore, images can be obtained in multiple planes without losing image quality as is seen with computer-reconstructed images with CT. MRI also provides superior soft tissue discrimination compared with CT. Consequently, MRI is my preferred method of imaging the lumbosacral articulation.

Figure 12: An axial plane MRI at the level of the lumbosacral intervertebral disk space in a dog. On the right side is a T2-weighted image and on the left is a T1-weighted image. Degeneration of the nucleus pulposus (arrowhead) is evidenced by a lack of hyperintensity on the T2-weighted image. Narrowing of the vertebral canal and loss of epidural fat are also present (long arrow). Additionally, ventral and lateral spondylosis is present (short arrows); Figure 13: An axial plane T2-weighted MRI of the level of the caudal aspect of the L7 vertebra in a dog. Note the lateralized intervertebral disk herniation within the intervertebral foramen (arrow). The normal intervertebral foramen is outlined by the arrowheads.
MRI features in dogs with degenerative lumbosacral stenosis include degeneration of the nucleus pulposus as evidenced by a decreased signal intensity on a T2-weighted image, protrusion of the annulus fibrosis, narrowing of the vertebral canal, loss of epidural fat overlying the intervertebral disk herniation (Figure 11), compression of the L7 nerve root within the intervertebral foramen, compression of the sacral and coccygeal nerve roots, and degenerative changes in the articular processes (Figure 12).34,35 Occasionally, lateralized intervertebral disk material can be seen in the intervertebral foramen (Figure 13). Unfortunately, as with all other imaging modalities, MRI features do not necessarily correlate with clinical findings, so be careful when trying to attribute imaging results to clinical signs.32,36 Instead, imaging findings should be used to support neurologic examination findings.


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