Atlas of RADIOGRAPHIC inteRpretation
site of the lesion, cranial to the lesion in a cisternal myelogram, or caudal to the lesion in a lumbar myelogram. This type of lesions includes intramedullary tumours (e.g. ependymoma, astrocytoma), intramedullary haemorrhage or oedema, hydromyelia, syringomyelia and granulomatous meningoencepahlitis. Other contrast techniques may be used to examine the spine instead of myelography, but their application is much more limited. Epidurography involves introducing the contrast medium (intentionally, not by mistake) in the epidural space, generally at the sacrococcygeal junction. It has been recommended for the detection of lesions in the cauda equina. The interpretation of the results of this technique is often difficult. Discography involves introducing contrast medium in the intervertebral space, but is hardly used in cats and dogs.
Computed tomography offers excellent images of the bones that form the spine, but it is not as good as magnetic resonance imaging for the definition of its soft tissues.
Congenital disorders
Hemivertebrae generally appear in the thoracic spine and are usually associated with kyphosis (dorsal deviation of the spine). They occasionally become clinically significant when they cause spinal cord compression, which can be assessed by means of myelography or advanced techniques (magnetic resonance imaging –fig. 4.10.– or computed tomographic myelography).
Hemivertebra
Block vertebra
It is due to an incomplete development of the vertebral body. It may affect one or several vertebrae. Hemivertebra may have a butterfly shape on ventrodorsal radiographs (fig. 4.8) or a “wedge” shape on lateral or ventrodorsal radiographs (fig. 4.9). Compensatory morphological changes in the adjacent vertebrae can usually be observed.
Two or more adjacent vertebral bodies appear partially or totally fused, with no intervertebral disc (fig. 4.11). This generally has no clinical significance.
Figure 4.7. Myelographic pattern of an intramedullary lesion. The width of the contrast columns decreases around
Transitional vertebra This occurs when the vertebrae of the atlantoaxial, cervical-thoracic, thoracolumbar, lumbosacral or sacroccygeal junction take morphological characteristics of the
Figure 4.10. Magnetic resonance image of the thoracolumbar spine of a dog with multiple vertebral deformations causing angulation of the spinal canal and spinal cord compression (arrow).
the spinal cord lesion. An enlargement of the dorsal contrast column, cranial to the site of the lesion, can be observed.
a
b
S1 Figure 4.8. Ventrodorsal radiograph of the
thoracic spine of a Bulldog with several “butterfly” vertebrae (arrows). Figure 4.9. Lateral radiograph of the cervical spine of a dog with several “wedge” vertebrae (arrows).
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Spine
in small animals
Normal radiographic anatomy of the
lumbosacral spine http://goo.gl/KC640
vertebrae of both regions (they totally or partially have the shape of the previous or next vertebra): ■■ Lumbarisation: the S1 vertebra appears separated from the rest of the sacrum, and may have one or two transverse processes, similar to those of the lumbar vertebrae. ■■ Sacralisation: the transverse process of L7 is fused with the wing of the sacrum and may articulate with the ilium. This alteration may cause lumbosacral instability and degeneration of the intervertebral disc (fig. 4.13), leading to cauda equina syndrome. It
Figure 4.11. Lateral radiograph of the cervical spine of a dog whose
C3 and C4 are fused (block vertebra).
Figure 4.12. Lateral (a) and
ventrodorsal (b) views of the lumbosacral area of the spine of a dog with lumbarisation of the sacrum. In the lateral view, a radiotransparent line (white arrow) can be seen, which separates the S1 vertebra from the rest of the sacrum. In the ventrodorsal view, a transverse process (black arrow) can be identified on S1. Spondylosis at L7-S1 can be observed on both radiographs.
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