Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

696 Small Animal Radiolo g y and Ultrasono graphy
FIG. 6-44 A 9-year-old male mixed
breed dog with dyschezia. The lateral
radiograph of the caudal lumbar
spine revealed “fluffy” periosteal new
bone formation affecting the ventral
aspects of L7, L6, and L5 (open black
arrow). Differential diagnoses
include metastatic neoplasia of the
prostate or other perineal organ and
infection. Diagnosis: Metastatic prostatic
adenocarcinoma.
reported to metastasize to the lumbar, sacral, or caudal vertebrae. In these cases periosteal
new bone formation or bony lysis may be observed. The ventral aspects of the fifth through
seventh lumbar vertebral bodies are affected most often (Fig. 6-44). The bony proliferation
may occur in association with tumor spread to the sublumbar (iliac) lymph nodes, with no
histologic evidence of tumor within the vertebral bodies themselves.
Spinal cord or nerve root tumors may occur and may produce erosions of the pedicle or
arch, but they usually produce no bony changes and must be documented by myelography.
Tumors may metastasize to the spinal canal without involving the vertebral body or the
spinal cord. These tumors usually exhibit no survey radiographic changes and can be identified
only by myelography. They will appear as extradural lesions (Fig. 6-45). 186
Spinal Cord and Nerve Root Tumors. Neoplasia of the spinal cord or spinal nerves may
have some subtle survey radiographic changes, but most are difficult to diagnose without
myelography. 187 Survey radiographs may reveal enlarged neural foramina or erosion of the
pedicles or laminae. An enlarged neural foramen may be apparent on either the ventrodorsal
or lateral view (Fig. 6-46). Comparison with the adjacent neural foramina is helpful
in recognizing this abnormality. Erosion of a pedicle, best seen on the ventrodorsal view,
appears as a loss of the sclerotic border medial to the pedicle, particularly as compared with
those pedicles cranial and caudal to it (Fig. 6-47). Careful positioning is essential for recognition
of this change. Overlying gas or ingesta may mimic or obscure this radiographic
abnormality. Erosion of the laminae is manifested as a loss of the sclerotic border of the
ventral-most part of the roof of the spinal canal (Fig. 6-48). This should also be compared
with the appearance of those vertebrae that are cranial and caudal to the affected one.
Tumors of the spinal cord may manifest with an intramedullary myelographic pattern.
Primary tumors of the spinal cord may include ependymoma, medulloepithelioma, neuroepithelioma,
lymphoma, or astrocytoma. 188-191 One unusual tumor that is usually
intramedullary (typically located from T10 to L3) and typically occurs in young dogs is
nephroblastoma. 192-198 This tumor is presumed to be due to remnants of the renal primordium
that become trapped within the dura. 195 In a few cases these tumors have
become apparent as extramedullary-intradural masses. 199,200 Metastatic tumors also have
been described that manifested as intramedullary lesions. 201-204
Tumors of the spinal cord or nearby associated structures may appear as
extramedullary-intradural masses. These are associated most commonly with neurofibroma
or meningioma. 205 Other tumors (e.g., nephroblastoma and metastatic tumors)
also may become apparent in this manner. 199,200
O S T E O C H O N D R O S I S
Osteochondrosis of the spine is rare. Lesions that resemble osteochondrosis have been
reported in association with cervical vertebral malformation. 206 Whether these lesions are
primary and cause the clinical signs or are secondary to the cervical vertebral malformation
is unknown. The lesions appear similar to osteochondrosis histologically. However,
they may be the result of degenerative joint disease and may not be the same as osteo-