A 4-month-old sexually intact male Balinese weighing 3.1 kg (6.8 lb) was referred for evaluation because of progressive paraparesis with no history of precipitating trauma. Six days prior to evaluation, the cat developed signs of decreased mobility and appetite. Lateral thoracic radiography had revealed lytic changes without periosteal reaction to the pedicle and the lamina of the T11 vertebra (Figure 1). Despite treatment for suspected diskospondylitis or osteomyelitis, the cat developed dyschezia and paraparesis progressed.
Lateral radiographic view of the thoracolumbar portion of the vertebral column of a 4-month-old Balinese that was evaluated because of progressive paraparesis with no history of precipitating trauma. Notice the permeative osteolysis of the pedicle and lamina of the T11 vertebra without periosteal reaction. No sclerotic or hyperplastic changes are evident. The T11 vertebral body is notated by an asterisk. A pin has been inserted into the spinous process of the T12 vertebra.
Citation: Journal of the American Veterinary Medical Association 256, 7; 10.2460/javma.256.7.771
At the referral evaluation, the cat was bright, alert, and responsive. The cat was ambulatory but would stand with all joints of the pelvic limbs in a moderate degree of flexion. General physical examination findings were considered normal; a neurologic evaluation was performed.
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 | Rule out location |
|---|---|
| Abnormal postural reactions in the pelvic limbs | T3-L3 myelopathy or a disease affecting the L4-S1 spinal cord segments and associated nerve roots, nerves, neuromuscular junctions, or muscles |
| Progressive ambulatory paraparesis with crouched posture in the pelvic limbs | T3-L3 myelopathy or a disease affecting the L4-S1 spinal cord segments and associated nerve roots, nerves, neuromuscular junctions, or muscles |
| Upper motor neuron pelvic limb proprioceptive ataxia | Focal or diffuse T3-L3 myelopathy |
| Cutaneous trunci reflex absent caudal to the thoracolumbar junction | Focal spinal cord lesion cranial to the T13-L1 junction but caudal to the T9-T10 spinal cord segments |
| Convergent strabismus | Likely normal breed variation or disorder of cranial nerve VI |
Likely location of 1 lesion
Paraparesis and abnormal postural reactions with normal myotatic and withdrawal reflexes in the pelvic limbs is consistent with a focal or diffuse lesion affecting the T3-L3 spinal cord segments. The finding of a cutoff of the cutaneous trunci reflex (caudal to which the reflex is decreased to absent) is consistent with a focal spinal cord lesion at 1 to 4 vertebrae cranial to where the reflex is absent. On the basis of signalment, normal mentation, and lack of additional cranial nerve deficits, the convergent strabismus is considered an incidental breed variation.
Etiologic diagnosis—Primary differential diagnoses for progressive T3-L3 myelopathy in a young cat included infectious disease, anomalous developmental disorders, and neoplastic causes. Radiographic changes of the T11 vertebra were suggestive of infectious diseases, such as bacterial osteomyelitis or osteomyelitis secondary to fungal disease (ie infection with Cryptococcus spp). Toxoplasma gondii infection was an unlikely cause of osteomyelitis but was included as a differential diagnosis because of the cat's signalment. Infection with FeLV or FIV and feline infectious peritonitis were considered unlikely primary conditions. Despite the cat's age, the radiographic changes prompted consideration of a neoplastic process, such as lymphoma, osteosarcoma, fibrosarcoma, or chondrosarcoma. Other neoplasms, such as nerve sheath neoplasm, meningioma, or glioma, were considered unlikely. Initial diagnostic testing included a CBC and serum biochemical analysis. Magnetic resonance imaging of the vertebral column and spinal cord was performed to assess structural abnormalities of the spinal cord, nerves, or vertebral column. A sample of CSF was obtained from the cerebellomedullary cistern and submitted for cytologic analysis to screen for infectious or neoplastic disease. A serum sample was submitted for T gondii IgG and IgM quantification via immunofluorescent assay and Cryptococcus antigen testing via latex agglutination. Testing for circulating FeLV antigen and anti-FIV antibody could have been performed given a potential diagnosis of lymphoma but was not considered necessary prior to MRI.
Diagnostic test findings—Results of the CBC were within reference intervals. Serum biochemistry analysis revealed mildly high amylase activity (1,135 U/L; reference interval, 300 to 1,100 U/L) and mild hyperphosphatemia (9.1 mg/dL; reference interval, 3.4 to 8.5 mg/dL) with no other abnormalities. The mildly high amylase activity was considered normal patient variability; the hyperphosphatemia was considered age appropriate. The cat was anesthetized, and MRI of the vertebral column was performed with a 1.5-T scanner.a Multiplanar (sagittal, transverse, and dorsal) images were obtained by use of the following sequences: T2-weighted, T1-weighted pre- and postcontrast, fast imaging employing steady-state acquisition, and gradient recalled echo. A proliferative extradural mass originating from the T11 vertebral body and extending into the vertebral canal ventral to and to the left of the spinal cord was found (Figure 2). This mass resulted in severe spinal cord displacement to the right, leading to deformation and compression of the spinal cord with complete attenuation of the surrounding CSF signal (Figure 3). There was a moderate degree of intramedullary T2-hyperintensity, compared with the appearance of normal spinal cord, at the level of and just cranial to the T11 vertebra. A large signal void was associated with the T11 vertebral body lesion on the gradient recalled echo sequence. The mass was strongly, but heterogeneously, contrast enhancing on T1-weighted postcontrast sequences following administration of gadopentate dimeglumine. The revised differential diagnoses given the MRI findings included a neoplastic process and a granulomatous process with secondary hemorrhage (seen as hypointensity or signal void on the gradient recalled echo sequence). A hematoma was considered less likely because of the radiographic evidence of lytic changes of the T11 vertebral body as well as lack of historical trauma. Results of the CSF sample analysis and testing for Toxoplasma IgG and IgM and Cryptococcus antigen were considered normal.
A T2-weighted sagittal MRI image of the thoracolumbar portion of the vertebral column of the cat in Figure 1. Notice the hyperintense extra-axial mass affecting the T11 vertebra (asterisk). Cranial is to the left and caudal is toward the right in this image.
Citation: Journal of the American Veterinary Medical Association 256, 7; 10.2460/javma.256.7.771
Magnetic resonance images of the thoracolumbar portion of the vertebral column of the cat in Figure 1. A—Postcontrast T1-weighted dorsal image of the thoracolumbar spinal cord. A contrast-enhancing extradural mass has caused right-sided displacement of the spinal cord at the level of the T11 vertebra (asterisk). The arrowheads denote the deviation of the spinal cord. B—Postcontrast T1-weighted transverse image obtained at the level of the T11 vertebra. The heterogeneously contrast-enhancing mass (outlined by 4 arrowheads) has caused destruction of the normal anatomic features of the T11 vertebra and right-sided displacement of the spinal cord (asterisk). In both panels, left (L) and right (R) sides are marked.
Citation: Journal of the American Veterinary Medical Association 256, 7; 10.2460/javma.256.7.771
A T10-T12 left-sided hemilaminectomy was performed to remove the lesion and achieve decompression of the spinal cord. During surgery, the lamina and the pedicle of the T11 vertebra appeared purple with proliferative tissue covering the affected zygapophyseal joint. The spinal cord was decompressed, and samples of the mass were submitted for histologic analysis and microbial culture and antimicrobial susceptibility testing. The remainder of the surgery was unremarkable, and the cat recovered from anesthesia uneventfully. There was no growth on direct plating media and broth culture after 72 hours. Histologic examination of sections of the mass revealed a vascular hamartoma.
Comments
Hamartomas are rare, benign, congenital masses arising from aberrant growth of local tissue.1 Theoretically, they can originate from any histologic cell type and have been previously detected in the stomach, sweat glands, kidneys, spinal cord, brain, peripheral nerves, skin, bones, gingival mucosa, and nasal mucosa of dogs and cats.2,3 Four previous reports3–6 of hamartomas affecting neurologic function in cats all involved vascular hamartomas of the cerebrum, cerebellum, or cervical or lumbar portion of the spinal cord. Because hamartomas are considered histologically benign without local invasion, clinical signs relate to local dysfunction resulting from increased pressure and displacement of normal tissue. Hamartomas are congenital lesions that are most often diagnosed in young animals. However, there are reports of hamartomas in geriatric animals owing to the slow-growing nature of the lesions and often the late onset of clinical signs.2 Once clinical signs are evident, the standard of treatment is resection.
Although hamartomas are considered benign, there has been 1 report7 of malignant transformation of colorectal hamartomatous polyps with metastasis to a local lymph node in a dog. In animals, there is no correlation with any genetic mutation; however, both heritable and spontaneous germline mutations in the phosphatase and tensin homolog (PTEN) gene on chromosome 10 are associated with PTEN hamartoma tumor syndrome in humans. The PTEN gene acts as a tumor suppressor by signaling cells to stop dividing. Mutation of 1 copy of the PTEN gene accounts for the development of multiple hamartomas and predisposes an affected human to development of neoplastic disease.8
Two previous reports3,6 have described CT and MRI characteristics of spinal vascular hamartomas in young cats (15 months and 9 months old) that had good outcomes following surgical intervention. In those cats, the cervical or lumbar portion of the spinal cord was affected. In 1 case,3 there was excessive bleeding during surgery and, in both cases, gross abnormalities of the affected vertebrae similar to those of the cat of the present report were described. To our knowledge, this is the first report of a vascular hamartoma associated with the thoracic portion of the vertebral column in a cat. Vascular hamartoma should be considered a differential diagnosis in any young cat with progressive myelopathy.
The cat of the present report recovered uneventfully from surgery. At the time of discharge from the hospital 2 days after surgery, the cat was nonambulatory and paraparetic with strong motor function evident when its hind region was supported. Postoperative follow-up was performed at 2 and 6 weeks. At the 6-week recheck examination, the cat had improved considerably and was ambulatory with mild residual pelvic limb ataxia. The cat was subsequently lost to follow-up.
Acknowledgments
No third-party funding or support was received in the writing or publication of the manuscript.
Footnotes
2005 Mobile GE 9X-LX Echospeed Plus 1.5T short bore (CXK4) MRI scanner, GE Healthcare, Boston, Mass.
References
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