What Is Your Diagnosis?

Daniel J. VanderHart Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

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David J. Reese Department of Diagnostic Imaging, College of Veterinary Medicine, Murdoch University, Murdoch, WA 6150, Australia.

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Shari M. Greenberg New England Veterinary Center and Cancer Care, 955 Kennedy Rd, Windsor, CT 06095.

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History

A 39-kg (86-lb) 9-year-old sexually intact female Rottweiler was referred because of a 4-day history of left pelvic limb lameness that had progressed to paraparesis. On physical examination, tachycardia (170 beats/min) and a high body temperature of 39.8°C (103.7°F) were found. Neurologic examination findings included pelvic limb paraplegia with retained deep pain perception of the pelvic limbs, signs of pain elicited with palpation of the midlumbar portion of the vertebral column, absent panniculus reflex caudal to L1, and extensor rigidity of the thoracic limbs. Findings on CBC were unremarkable. The only serum biochemical abnormality was mildly high alkaline phosphatase activity (129 U/L; reference range, 16 to 111 U/L). Thoracic radiography revealed a lobulated, 6 × 3.5-cm soft tissue mass in the accessory lung lobe. Orthogonal radiographs of the lumbar vertebral column were obtained; however, only the lateral view is provided (Figure 1).

Figure 1—
Figure 1—

Lateral radiographic view of the lumbar portion of the vertebral column in a 39-kg (86-lb) 9-year-old sexually intact female Rottweiler with a 4-day history of left pelvic limb lameness that had progressed to paraparesis.

Citation: Journal of the American Veterinary Medical Association 244, 8; 10.2460/javma.244.8.899

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Diagnostic Imaging Findings and Interpretation

A thin, well-defined, mineral opaque line is seen superimposed over the vertebral canal. This line parallels the ventral margin of the vertebral canal, with the exception of a focal dorsal displacement extending from the level of the L2-3 intervertebral disk space caudally to the level of the cranial aspect of the L4 vertebral body (Figure 2). Throughout the caudal aspect of the thoracic portion of the vertebral column and the entire lumbar portion of the vertebral column, there is well-defined, smoothly margined, osseous proliferation along the ventral aspects of the vertebral endplates compatible with ventral spondylosis deformans. This is most severe at the L2-3 and lumbosacral intervertebral disk spaces. The radiographic interpretation is dorsal displacement of the ossified dura at the level of L3, which supports a ventral extradural lesion. On the basis of the clinical signs and radiographic findings, concurrent spinal cord compression was suspected. Differential diagnoses for the extradural lesion, considering location and signalment, included neoplasia (eg, primary bone or metastatic neoplasia), intervertebral disk herniation, fungal granuloma, hematoma, or hemorrhage.

Figure 2—
Figure 2—

Same radiographic image as in Figure 1. Notice the well-defined, thin, linear region of mineral opacity, representing dural ossification (arrowheads). There is dorsal displacement of the ossified dura, which is suggestive of a ventral extradural spinal cord compression at the level of L3 (arrows). Throughout the caudal aspect of the thoracic portion of the vertebral column and the entire lumbar portion of the vertebral column, also notice the well-defined, smoothly margined, osseous proliferation along the ventral aspects of the vertebral endplates compatible with ventral spondylosis deformans. This is most severe at the L2-3 and lumbosacral intervertebral disk spaces.

Citation: Journal of the American Veterinary Medical Association 244, 8; 10.2460/javma.244.8.899

Magnetic resonance imaging of the lumbar portion of the vertebral column was performed, and a large, heterogenous mass was identified effacing the L3 vertebral body with dorsal and ventral extension (Figure 3). The dorsal extension into the vertebral canal resulted in epidural and subarachnoid attenuation and dorsal displacement of the spinal cord. This correlated with the findings on survey radiography.

Figure 3—
Figure 3—

Sagittal T2-weighted MRI image of the lumbar portion of the vertebral column of the same dog as in Figure 1. Notice the extent of the L3 vertebral body mass (arrows). For reference, the L2 vertebral body is labeled (asterisk).

Citation: Journal of the American Veterinary Medical Association 244, 8; 10.2460/javma.244.8.899

Treatment and Outcome

A cytologic diagnosis of histiocytic sarcoma was made on evaluation of a fine-needle aspirate of the mass obtained under ultrasound guidance. Within days, the patient's clinical status deteriorated, with the loss of deep pain perception in the pelvic limbs. Euthanasia was recommended.

Comments

For the dog of the present report, possible further imaging modalities following radiography included CT or MRI. A myelogram would have likely contributed minimal additional information, given that the ossified dura already defined an extradural lesion on radiographic evaluation. The choice of imaging modality at our institution for defining lesions of the vertebral canal is MRI; however, CT would have also aided in further characterizing this lesion.

Disseminated histiocytic sarcoma is a multicentric disease that can involve lymph nodes, bone marrow, lungs, spleen, and liver.1 Histiocytic sarcoma has been reported to involve the axial skeleton, with Rottweilers and Golden Retrievers overrepresented.2

Ossification of the dura indirectly defines the margins of the spinal cord, which has resulted in the term automyelogram.3 This myelographic-like effect was useful in the case described here for localizing the site of spinal cord compression. Dural ossification has been reported as a common necropsy finding in dogs; however, it is rarely reported on survey radiographs of the vertebral column. Dural ossification is a form of metaplasia and involves the formation of plaques of bone within the dura of the spinal cord, most often within the cervical and lumbar regions.4 Dural ossification is generally considered an incidental finding; however, it has been associated with clinical disease.5 If seen, however, dural ossification can be a useful adjunctive radiographic finding for identifying extradural spinal cord compression, as it was in the dog described in this report.

  • 1. Affolter VK, Moore PF. Localized and disseminated histiocytic sarcoma of dendritic cell origin in dogs. Vet Pathol 2002;39:7483.

  • 2. Schultz RM, Puchalski SM, Kent M, et al. Skeletal lesions of histiocytic sarcoma in nineteen dogs. Vet Radiol Ultrasound 2007;48:539543.

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  • 3. Lamb CR, Guthrie S. Radiology corner: a rare example of an automyelogram. Vet Radiol Ultrasound 1995;36:383.

  • 4. Morgan JP. Spinal dural ossification in the dog: incidence and distribution based on a radiographic study. Vet Radiol 1969;10:4348.

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  • 5. Wilson JW, Greene HJ, Leipold HW. Osseous metaplasia of the spinal dura mater in a Great Dane. J Am Vet Med Assoc 1975;167:7577.

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