Page 340 - Atlas of Small Animal CT and MRI

330 Atlas of Small Animal CT and MRI

following intravenous contrast administration on CT MR features include T1 hypo‐ to isointensity, T2
images. CT myelography can be used to assess presence hyperintensity, and moderate homogeneous enhance­
and location of spinal cord compression. On MR images, ment (Figure 3.4.12). Diffuse meningeal enhancement
plasmacytomas are almost purely osteolytic, T1 iso‐ to has also been reported. The compartment of origin
4,17
hyperintense and T2 hyperintense compared to epaxial can sometimes be determined, particularly by evaluat­
musculature, and variably but uniformly enhance follow­ ing the distribution of T2 hyperintense cerebrospinal
ing intravenous contrast administration (Figure 3.4.8). fluid in relation to the tumor, although large masses may
Three‐dimensional gradient‐echo sequences can be used be more difficult to localize.
to more accurately assess bone destruction.
CT and MR features of multiple myeloma include Other neoplasms
multiple poorly margined to well‐demarcated foci of Rarely, other tumors can originate within the extradural
osteolysis, which are often most abundant in the verte­ space as either primary or metastatic neoplasms.
bral column (Figure 3.4.9). Imaging features will vary widely depending on cell type
(Figure 3.4.13).

Metastatic neoplasia
Both carcinomas and soft sarcomas metastasize to the Intradural–extramedullary neoplasia
vertebral column, with carcinoma metastasis occurring Features of intracranial nervous system neoplasms
more often. Lesions are predominantly osteodestruc­ have been described in Chapters 2.8 and 2.10 and spi­
7–9
tive and can include an extravertebral component when nal neoplasms of the same cell type often have similar
cortical margins are breached. CT imaging features vary imaging characteristics. The most common intra­
depending on cell type but generally include focal or dural–extramedullary neoplasms include meningi­
multifocal osteolysis and a soft‐tissue attenuating mass oma, peripheral nerve sheath tumor, nephroblastoma,
that variably enhances following intravenous contrast cerebrospinal fluid disseminated metastasis, and
administration. Pathologic fracture can occur when round cell tumors, such as lymphoma and histiocytic
structural integrity of cortical bone is compromised. A sarcoma. 4,10,18–22
periosteal productive reaction is occasionally present
with soft‐tissue tumor metastases, and osteosarcoma meta­ Meningioma
stases can have a mixed osteoproductive/destructive Meningioma is the most common central nervous sys­
appearance. MR features include a space‐occupying
osteolytic soft‐tissue mass that is variably T1 intense, T2 tem neoplasm of the spinal cord in dogs. Median age at
onset of clinical signs is 9 years, and Golden Retrievers
hyperintense, and usually intensely enhancing following 23
intravenous contrast administration (Figures 3.4.10, and Boxers appear to be overrepresented. Most canine
spinal meningiomas are World Health Organization
3.4.11). Three‐dimensional gradient‐echo sequences
can be used for more accurate assessment of the extent (WHO) grade I or II, with a small minority being more
biologically aggressive grade III. Nearly 70% are located
of bone destruction.
in the cervical region, about 25% are lumbar, and the
remainder are thoracic or multifocal. Although less
22
Lymphoma common, spinal meningioma has also been reported in
Lymphoma associated with the vertebral column and the cat. 24
spinal cord can be extradural, intradural– extramedullary, On CT images, spinal meningiomas are soft‐tissue
or intramedullary (intrinsic), although the latter is attenuating space‐occupying masses within the vertebral
reported to be less common. 4,10–15 Lymphoma is the most canal that variably displace and compress the spinal cord,
common spinal neoplasm in cats and is often a compo­ depending on tumor size in relation to the vertebral canal
nent of multicentric disease. 10,12,15 diameter. Meningiomas uniformly enhance following
On CT images, extradural lymphoma masses are intravenous contrast administration and appear as a
soft‐tissue attenuating and minimally to mildly contrast contrast‐filling defect within the subarachnoid space on
enhancing following intravenous contrast administra­ CT myelography (Figure 3.4.14). On MR images, menin­
tion. CT myelography can be used to document spinal giomas are mildly to moderately T1 hyperintense, mildly
16
cord compression and to determine the compartment of to markedly T2 hyperintense, and uniformly and
origin, with extrinsic masses producing eccentric spinal intensely contrast enhancing. A dural tail sign may be
cord displacement and compression and intrinsic lesions present in some instances but is not consistent.
producing a focal increase in cord diameter and annular Intradural–extramedullary localization is supported by
attenuation of the subarachnoid contrast column. peripheral T2/STIR hyperintensity due to subarachnoid

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