A 10-year-old 4.8-kg (10.6-lb) spayed female domestic shorthair cat was evaluated because of a 4-week history of progressive asymmetrical paraparesis (left pelvic limb more affected than the right pelvic limb). Palpation of the lumbar portion of the vertebral column elicited mild signs of pain, which resolved following treatment with anti-inflammatory doses of prednisolonea (1 mg/kg/d [0.45 mg/lb/d], PO, for 5 days [tapering dosage]). However, the cat's paraparesis did not improve and continued to progress despite corticosteroid treatment and administration of clindamycin hydrochlorideb (12 mg/kg [5.5 mg/lb], PO, q 12 h) for 4 weeks. Results of radiography and abdominal ultrasonography were unremarkable. Clinicopathologic findings included mild leukocytosis with mild neutrophilia. There were no notable findings on general physical examination. When the cat was ambulatory with mild paraparesis (worse on the left side), MRI and analysis of a CSF sample had been performed; a neurologic examination was performed 3 weeks later.
What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page.
Assessment Anatomic diagnosis
| Problem | |
|---|---|
| Monoplegia of the left pelvic limb with blunted deep pain perception and reduced segmental spinal reflexes in this limb | Lateralization to left side of the spinal cord, such as the L4-S3 spinal cord segments or left lumbar plexus and peripheral nerves |
| Right pelvic limb paresis with decreased postural reactions and normal segmental spinal reflexes in this limb | T3-L3 spinal cord segments (given the apparently normal reflexes in the right pelvic limb) |
| Leukocytosis with neutrophilia | Systemic inflammation, infection, or stress leukogram |
Likely location of 1 lesion
Left lateralized L4-S3 myelopathy with extension into the T3-L3 spinal cord segment.
Etiologic diagnosis—The primary differential diagnoses for lateralized L4-S3 myelopathy in an older cat included neoplasia (peripheral nerve sheath tumor, lymphoma, glioma, meningioma, compressive osseous mass, or a metastatic lesion), granuloma, infectious disease (toxoplasmosis, feline infectious peritonitis, or fungal disease), lateralized intervertebral disk herniation, or ischemic myelopathy (fibrocartilaginous embolization or hyaline arteriopathy). Diagnostic testing included a CBC, serum biochemical analysis, assessment of serum thyroxine concentration, urinalysis, cytologic evaluation of a blood smear, and radiography of the lumbar portion of the vertebral column and the left pelvic limb. Assessments for serum antibodies against Toxoplasma gondii, FIV, and feline coronavirus and for FeLV and Cryptococcus antigens were performed to evaluate for infectious causes. Abdominal ultrasonography was performed to screen for systemic disease and neoplasia. Magnetic resonance imaging of the thoracolumbar and lumbosacral portions of the vertebral column was performed to identify any structural lesions. Analysis of a CSF sample was performed to evaluate for inflammatory disease, infection, or neoplasia in the CNS.
Diagnostic test findings—The initial CBC revealed mild leukocytosis (23.4 × 103 WBCs/μL; reference interval, 3.5 × 103 WBCs/μL to 16.0 × 103 WBCs/μL); a differential cell count revealed 84% neutrophils. The platelet count was 94 × 103 platelets/μL (reference interval, 300 × 103 platelets/μL to 800 × 103 platelets/μL), and examination of a blood smear revealed an adequate number of platelets. Serum biochemical analysis revealed cholesterol concentration of 273 mg/dL (reference interval, 75 to 175 mg/dL). Serum thyroxine concentration and results of urinalysis were within reference intervals. Abdominal ultrasonography revealed mild degenerative changes in the left kidney. Testing for infectious diseases yielded negative results. Magnetic resonance imagingc of the thoracolumbar portion of the vertebral column revealed a large (0.7 × 0.8 × 1.1-cm) intramedullary spinal cord lesion at the level of the L5 vertebral body and a second smaller intramedullary lesion in the left dorsal aspect of the spinal cord at the level of L4 (Figure 1). The lesion at the L5 vertebral body had enlarged and expanded the spinal cord at this level with attenuation of the surrounding CSF signal of the subarachnoid space. Compared with the surrounding spinal cord parenchyma, both lesions were hyperintense on T2-weighted and short tau inversion recovery images and isointense on T1-weighted images. There was no contrast enhancement of either lesion following administration of gadopentetate dimeglumine.d A sample of CSF was obtained by cisternal puncture and analyzed; no abnormalities were detected. The intramedullary lesions were considered most likely to be gliomas (ependymoma, astrocytoma, or oligodendroglioma) that did not respond to glucocorticoid or antimicrobial treatment.
Sagittal (A and D) and transverse (B and C) plane T2-weighted (A, B, and C) and short tau inversion recovery (D) MRI images of the lumbar portion of the vertebral column of a 10-year-old domestic shorthair cat that had a 4-week history of progressive asymmetric paraparesis. At the level of the L5 vertebra, there is a focal intramedullary mass (white arrow) expanding the spinal cord; a second similar lesion at the level of L4 is visible on the sagittal images. Both lesions are hyperintense on T2-weighted images (A, B, and C) and the short tau inversion recovery image (D). The lesion at L4 (yellow arrow) is hyperintense in the left dorsal aspect of the cord on the transverse T2-weighted image (C).
Citation: Journal of the American Veterinary Medical Association 255, 1; 10.2460/javma.255.1.55
Sagittal (A and D) and transverse (B and C) plane T2-weighted (A, B, and C) and short tau inversion recovery (D) MRI images of the lumbar portion of the vertebral column of a 10-year-old domestic shorthair cat that had a 4-week history of progressive asymmetric paraparesis. At the level of the L5 vertebra, there is a focal intramedullary mass (white arrow) expanding the spinal cord; a second similar lesion at the level of L4 is visible on the sagittal images. Both lesions are hyperintense on T2-weighted images (A, B, and C) and the short tau inversion recovery image (D). The lesion at L4 (yellow arrow) is hyperintense in the left dorsal aspect of the cord on the transverse T2-weighted image (C).
Citation: Journal of the American Veterinary Medical Association 255, 1; 10.2460/javma.255.1.55
Sagittal (A and D) and transverse (B and C) plane T2-weighted (A, B, and C) and short tau inversion recovery (D) MRI images of the lumbar portion of the vertebral column of a 10-year-old domestic shorthair cat that had a 4-week history of progressive asymmetric paraparesis. At the level of the L5 vertebra, there is a focal intramedullary mass (white arrow) expanding the spinal cord; a second similar lesion at the level of L4 is visible on the sagittal images. Both lesions are hyperintense on T2-weighted images (A, B, and C) and the short tau inversion recovery image (D). The lesion at L4 (yellow arrow) is hyperintense in the left dorsal aspect of the cord on the transverse T2-weighted image (C).
Citation: Journal of the American Veterinary Medical Association 255, 1; 10.2460/javma.255.1.55
Comments
Intraparenchymal spinal cord lesions are relatively rare in cats. For the cat of the present report, a diagnosis of intramedullary glioma was made. Other differential diagnoses that were considered, such as ischemic myelopathies, may be associated with imaging characteristics similar to those of intraparenchymal spinal cord lesions, no CSF abnormalities, and a lack of response to glucocorticoid administration, but did not fit with this cat's clinical progression. Infectious causes were also considered as a possibility. In a study1 of 205 cats with spinal cord disease, infectious or inflammatory disease was the most common disease category (64 [31%] cats), followed by neoplasia (56 [27%] cats). Among the infectious or inflammatory disease subgroups, the most common disease was feline infectious peritonitis (33 [16%] cats); among the neoplasia subgroups, lymphosarcoma was most common (20 [10%] cats). Only 6 cats had intramedullary neoplasia, of which 3 (1.5%) had spinal cord gliomas.1 In that same study,1 asymmetrical deficits (such as monoparesis) were evident only in cats classified as having neoplastic or traumatic diseases. Infectious causes of spinal cord disease were considered less likely in the cat of the present report because of the asymmetric nature of clinical signs, lack of improvement following antimicrobial treatment, and negative results of infectious disease testing. A disk herniation could have been a traumatic cause of asymmetric deficits, but that was ruled out by the imaging findings, which indicated the presence of an intraparenchymal lesion.
Neoplasia emerged as the most likely cause of spinal cord disease in the cat of the present report, with CNS lymphosarcoma and glioma as the top differential diagnoses. Results of a retrospective study2 indicated that lymphosarcoma is the most common spinal cord neoplasm in cats. Of the 85 cats with spinal cord neoplasia in that study,2 33 (39%) had spinal cord lymphosarcoma, whereas only 8 (9%) had glial tumors. Spinal cord lymphosarcoma is generally reported to be a disease affecting young cats3; spinal cord gliomas typically affect older cats.4,5 In a study1 of 205 cats with spinal cord disease, the median age of cats with spinal cord lymphosarcoma was 4.5 years. In 2 recently published retrospective studies4,5 of cats with spinal cord gliomas, the median age was 8 years. Regarding the imaging findings for cats with spinal cord lymphosarcoma, the lesion is consistently contrast enhanced on T1-weighted MRI images.3 For the cat of the present report, the lack of contrast enhancement on MRI images, lack of neoplastic lymphocytes in the CSF sample, and lack of response to prednisone administration all supported a diagnosis of glioma rather than spinal cord lymphosarcoma.
There is little information about treatment outcomes for cats with intramedullary spinal cord tumors. To our knowledge, there are no reports in the veterinary medical literature of surgical treatments for spinal cord glial tumors in cats, and the benefit of tumor resection is likely low with high risk for postoperative neurologic deterioration. Little is known about the response rate for full-course, stereotactic, or hypofractionated radiation therapy, chemotherapy, or multimodal therapy. The owners of the cat of the present report opted for palliative treatment with administration of prednisolone (1 mg/kg/d), and the cat was euthanized within 3 weeks after undergoing diagnostic imaging because of its poor response to treatment and declining quality of life. In another study,5 2 cats with spinal cord gliomas were euthanized 2 weeks after palliative treatment with prednisolone.
A postmortem examination of the cat of the present report revealed an intraparenchymal spinal cord lesion at the level of the L3-L5 vertebrae. The neuroparenchyma was expanded by an unencapsulated, poorly demarcated neoplasm. Histologically, the neoplasm was comprised of an infiltrative population of glial cells that had mild to moderate nuclear pleomorphism. The mitotic index was 5 mitoses/10 hpf (100X). Intermixed with the neoplastic cell population were numerous tortuous and aggregated glomeruloid vessels. Immunohistochemical staining for glial fibrillary acidic protein (GFAP, an astrocytic marker) and oligodendrocyte transcription factor 2 (an oligodendrocytic marker) was performed. Neoplastic cells were negative for GFAP, although the cytoplasm of numerous interdigitating astrocytes intermixed with and surrounding neoplastic cells were strongly immunoreactive for GFAP. Approximately 30% to 50% of the nuclei within the neoplastic population had discrete, nuclear GFAP reactivity. This pattern of immunohistochemical staining, along with the histologic findings, were consistent with an oligodendroglioma.
There are only 22 reported cases2,4-9 of spinal cord gliomas in cats, and 13 of those cats had gliomas in the cervical portion of the spinal cord. Only 5 of the 22 cats had oligodendrogliomas, 1 of which had a tumor in the lumbar region of the spinal cord (level of L5 through L7).4 For most spinal cord gliomas in cats, the lesion contrast enhancement has a ring-like pattern on T1-weighted MRI images.2,5,6,10 Of the 7 cases of feline spinal cord gliomas with reported MRI findings, 5 had contrast enhancement with ring-like contrast enhancement on MRI images.2,5,6 The case described in the present report was unusual in that the glioma was an oligodendroglioma in the lumbar portion of the cat's spinal cord and the lesion was not associated with contrast enhancement on MRI images. Overall, glioma is an important differential diagnosis to consider in older cats for which there is a clinical suspicion of spinal cord neoplasia (regardless of anatomic location) and a lack of response to glucocorticoid or antimicrobial treatment. This report highlighted an example of progressive pelvic limb monoparesis in an older cat that was associated with unique diagnostic imaging findings of a lesion that was determined to be an oligodendroglioma.
Footnotes
Prednisolone, Lloyd Inc, Shenandoah, Iowa.
Clindamycin, Lannett Company Inc, Philadelphia, Pa.
1.0 Tesla GE LX Signa Echospeed MRI, GE Medical Systems, Milwaukee, Wis.
Dotarem, Guerbet LLC, Bloomington, Ind.
References
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