Spinal Canal Stenosis

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Fig. 8.38a You are looking at an axial CT image through a lower lumbar vertebral body. The spinal canal is severely stenosed by the bone itself—there is no sign of degeneration. This spinal canal stenosis is congenital in nature. Back problems are unavoidable and preprogrammed in these patients. b The vacuum phenomenon in this disk is well seen as well as the hypertrophic degenerative change in the intervertebral joints and the thickening of the posterior longitudinal ligament (the ligament that forms the posterior border of the spinal canal). This spinal canal stenosis is acquired and is due to chronic degenerative change.

Spinal Canal Morphologies

Fig. 8.40a The lumbar spine film of this patient shows no abnormality. A disk herniation is evident on MRI. The increases in transparency in projection over the upper and middle vertebral body are due to intestinal gas. b This axial CT image demonstrates the massive posterior prolapse of disk material into the spinal canal. The thecal sac is compressed and along with it the cauda equina.

Fig. 8.39 Scoliosis results in uneven distribution of axial loading forces to the spine. Eccentric biomechanical stress of the intervertebral disks leads to accelerated degeneration, further increasing the deformity over time. Note the dislocation of L4 relative to L5! Now take a little time for the second relevant finding on this radiograph, which is independent of the scoliosis. Remember the "satisfaction of search" we talked about in Chapter 4.

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Fig. 8.40a The lumbar spine film of this patient shows no abnormality. A disk herniation is evident on MRI. The increases in transparency in projection over the upper and middle vertebral body are due to intestinal gas. b This axial CT image demonstrates the massive posterior prolapse of disk material into the spinal canal. The thecal sac is compressed and along with it the cauda equina.

I Spondylodiskitis

Mri Spinal CanalMri Pics Abnormal Thecal Sac

Fig. 8.41 a This radiograph shows the loss of definition of the vertebral body end plates adjacent to the intervertebral disk space L3/L4. This is a strong hint in the direction of infectious spondylodiskitis. b The process has also caused a misalignment of L3 relative to L4. The ligaments have become flaccid or are destroyed; the spinal architecture is disturbed. c This

Fig. 8.41 a This radiograph shows the loss of definition of the vertebral body end plates adjacent to the intervertebral disk space L3/L4. This is a strong hint in the direction of infectious spondylodiskitis. b The process has also caused a misalignment of L3 relative to L4. The ligaments have become flaccid or are destroyed; the spinal architecture is disturbed. c This conventional tomogram illustrates even better the destruction of the end plates. Conventional tomography has ceased to be a diagnostic tool in spondylodiskitis but, boy, does this one look good. d The MR image shows the extent of the infection into the spinal canal and into the bordering vertebral bodies. It is the modality of choice for this entity.

I Abscess Locations in Spondylodiskitis

I Abscess Locations in Spondylodiskitis

Spondylodiskitis

Fig. 8.42 a This scan of the lower lumbar spine shows a sagittal image including vertebral bodies, disks, and the spinal canal. The signal of the spinal fluid tells you whether it is a T1-weighted or T2-weighted sequence (see Fig. 4.4a in Chapter 4). For better soft tissue delineation, intravenous contrast has been given. With the exception of the lowest level, all intervertebral disk spaces seem to be normal. At the L5/S1 level, contrast accumulates in the periphery of the disk space (arrow). b Spondylodiskitis may also be complicated by an epidural abscess. The fluid content of the abscess appears darkonT1-weighted images and is surrounded by an enhancing abscess wall (arrow). c This CT image of the lateral pelvis shows a pocket of fluid along the iliopsoas muscle. The space was filled with pus from a spondylodiskitis at the L3/L4 level that had descended along the muscle in a typical fashion. The abscess was drained under CT guidance by the interventional radiologist and material for a microbiological analysis was sent to the microbiology laboratory.

Fig. 8.42 a This scan of the lower lumbar spine shows a sagittal image including vertebral bodies, disks, and the spinal canal. The signal of the spinal fluid tells you whether it is a T1-weighted or T2-weighted sequence (see Fig. 4.4a in Chapter 4). For better soft tissue delineation, intravenous contrast has been given. With the exception of the lowest level, all intervertebral disk spaces seem to be normal. At the L5/S1 level, contrast accumulates in the periphery of the disk space (arrow). b Spondylodiskitis may also be complicated by an epidural abscess. The fluid content of the abscess appears darkonT1-weighted images and is surrounded by an enhancing abscess wall (arrow). c This CT image of the lateral pelvis shows a pocket of fluid along the iliopsoas muscle. The space was filled with pus from a spondylodiskitis at the L3/L4 level that had descended along the muscle in a typical fashion. The abscess was drained under CT guidance by the interventional radiologist and material for a microbiological analysis was sent to the microbiology laboratory.

f A suspected spondylodiskitis is one of the most important i emergency indications of magnetic resonance imaging.

Spondylolisthesis with spondylolysis (true spondylolisthesis) and without spondylolysis (pseudospondylo-listhesis): Spondylolisthesis is defined as the ventral slippage of a complete or partial vertebral body on the stationary vertebra underneath it. The so-called true spondylolisthesis is so frequent it could be called a natural variant (Fig. 8.43a, b). It is a complication of bilateral spondylolysis, which is a defect in the pars interarticularis of the vertebra, the osseous bridge between the upper and lower intervertebral facet. This pars may be dysplastic to start with and/or may fracture as a consequence of physical stress. It results in a division of the vertebra into an anterior part including the body and a dorsal part consisting of the lower intervertebral joint and the posterior arch. As the disk gives way under the increased strain, the vertebral body slips forward (just like a new ship slides into the water), leaving the separated arch and spinous process behind. Radiologically, spondylolysis is particularly well appreciated on oblique lumbar radiographs where the shape of a "Scottie dog" can be perceived (the head and ear of the dog is the upper intervertebral process, its body the lower intervertebral process). The defect in the pars interarticularis looks quite like the Scottie dog's collar (Fig. 8.43c, d).

In pseudospondylolisthesis the slippage is due to degenerative changes of the intervertebral joints (see above) as the whole vertebra moves forward. The resulting misalignment certainly may stenose the lateral neuroforami-na and the spinal canal. Neurological symptoms may develop as a consequence.

On lateral views of the spine, the extent of the vertebral slippage in both types of spondylolisthesis can be determined and classified according to Meyerding: The lower body's end plate is divided into quarters—from I through IV starting dorsally. A Meyerding I through IV is assigned depending on the amount of slippage relative to the lower body. Flexion and extension views of the spine are useful to detect potential instabilities.

Ankylosing spondylitis: Ankylosing spondylitis or Bech-terew disease is a seronegative spondylarthropathy, a member of the group of inflammatory arthropathies. The disease often occurs in conjunction with sacroiliitis (Fig. 8.44a). The ligaments—particularly those of the spine—may ossify, resulting in the famous "bamboo spine" appearance on plain radiography (Fig. 8.44b). The affected joints—such as the sacroiliac articulation—tend to fuse. The patients end up with a rigid axial skeleton, which can lead to dramatic spinal injuries after trivial trauma.

I True Spondylolisthesis (Spondylolysis)

True Spondylolisthesis

f

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Meyerding Grad

Fig. 8.43 a This radiograph shows the slippage of L4 relative to L5 to good advantage. The listhesis is classified as a Meyerding grade I-II. The defect in the pars interarticularis is also well seen in this patient (arrow). b That is not always the case. Draw one line along the anterior margin of the vertebral bodies and another along the posterior edge of the spinous processes (compare degenerative spondylolisthesis, Fig. 8.37b). The lines prove that the malalignment is one vertebral level higher posteriorly compared to ventrally—the spinous process and its vertebral body are disconnected. c On the oblique view, the silhouette of two "Scottie dogs" is visible. d In this case the upper dog runs around unrestrained while the lower dog wears a "leash"—the radiographic lucency that corresponds to the defect in the pars interarticularis of the affected vertebral body.

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