Page 328 - Atlas of Small Animal CT and MRI

318 Atlas of Small Animal CT and MRI

Imaging features vary widely and depend on the stage Imaging features of spondylitis include periosteal new
of the disease. CT features of early active disease can bone formation of the ventral and lateral margins of
include vertebral endplate osteolysis and intervertebral affected vertebral bodies. Underlying bone sclerosis may
joint space widening. In later phases of active disease, also be present depending on the duration and severity of
more pronounced endplate destruction is seen, which is infection, resulting in hyperattenuation on CT images
associated with underlying bone sclerosis, reactive new and hypointensity on T1 and T2 MR images. Cellulitis or
bone formation, and collapse of the disk space. If there is abscess is present with active disease, which will appear
significant proliferative soft‐tissue inflammatory response as a hypoattenuating sublumbar mass on CT images and
or intervertebral joint subluxation, spinal cord compres- a T1 hypointense, T2 hyperintense mass on MR images.
sion can occur with resultant neurologic signs. In the Marked, heterogeneous soft‐tissue contrast enhance-
convalescent or reparative phase, complete collapse of ment occurs on images of both modalities (Figure 3.3.8).
the joint may occur with bridging reactive new bone.
Soft tissues within the disk space, medullary bone, and Spinal cord, meninges, and epidural space
surrounding soft tissues moderately to markedly contrast Spinal epidural empyema
enhance during the active phases of disease, reflecting Infections within the spinal epidural space are uncom-
the presence of discitis, osteomyelitis, and cellulitis mon and can occur by direct extension of discospondyli-
(Figures 3.3.3, 3.3.4). tis or other local infection or through hematogenous
MR features of bacterial discospondylitis are similar dissemination. Signs include fever and progressive mye-
and include mixed T2 intensity within the disk space lopathy, which may have a compressive component. 19,20
and T1 hypointensity and T2 and STIR hyperintensity CT findings can be equivocal but include signs of
within affected vertebral bodies and adjacent soft tissues discospondylitis as described above. Subarachnoid and
during the early active phase of disease. The disk, epidural space contrast enhancement can be incomplete
medullary bone, and adjacent soft tissues intensely con- or nonuniform on CT myelographic images, and there
trast enhance during the active phases of disease may be evidence of focal, multifocal, or diffuse spinal
(Figure 3.3.5). MR may be less sensitive than CT for cord compression. 20
7,12
monitoring bone destruction and production in the MR features include mixed or increased T2 intensity
active and reparative phases, respectively. within the epidural space, as well as T2 hyperintensity
within the spinal cord at the site of infection. Moderate
Mycotic (granulomatous) discospondylitis diffuse or peripheral enhancement is seen following con-
Mycotic discospondylitis is almost always a component trast administration with both modalities (Figure 3.3.9). 19
of systemic infection with Aspergillus or Paecilomyces
species, although other fungi have also been reported. 13–17 Meningomyelitis
Age of onset is 2–8 years, and German Shepherd Dogs Infectious meningomyelitis is uncommon in both the
and females are highly overrepresented, accounting for dog and cat and can be viral, bacterial, mycotic, proto-
more than two thirds of reported patients. 15,16 Affected zoal, or parasitic. 7,15,21,22 Because of the spectrum of
dogs are thought to be immunocompromised, resulting infectious agents, clinical presentation varies widely, and
in multiorgan involvement. meningomyelitis may be only part of a systemic or mul-
Imaging features of mycotic discospondylitis are similar tiorgan disorder. Imaging reports of meningomyelitis in
to those of bacterial discospondylitis, and often multiple small animals are sparse, but in our experience MR imag-
intervertebral disks are affected (Figures 3.3.6, 3.3.7). ing features are also variable. In patients with pyogenic or
granulomatous meningomyelitis, fluid and solid‐material
Spondylitis collections in the subarachnoid space can have variable
In some geographic areas, inhaled plant awns can T1 intensity, T2 heterogeneity, and FLAIR hyperintensity.
migrate through airways and lung parenchyma and exit Meninges can intensely enhance following contrast
caudally into the cranial sublumbar region, following administration. Depending on the volume and character
the path of the attachment of the pars lumbalis of the of inflammatory material in the subarachnoid space, the
diaphragm to the ventral margins of the third and spinal cord or cauda equina can be displaced and com-
fourth lumbar vertebrae. Pyogranulomatous myositis pressed. Spinal cord parenchyma can be T1 hypointense
and frank abscess adjacent to the vertebrae lead to and T2 hyperintense, and cord diameter can be increased
spondylitis. 18 because of edema (Figures 3.3.10, 3.3.11).

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