A 2-year-old 5.2-kg (11.4-lb) neutered male domestic shorthair cat was referred because of a 6-week history of progressive pelvic limb ataxia and paraparesis. The owner reported that the cat's initial clinical signs were those of spinal discomfort, which progressed to marked paraparesis and ataxia when walking. Prior to referral, the cat had received a 2-week tapering dosage of orally administered dexamethasone, which temporarily alleviated the clinical signs; however, after this treatment was discontinued, the previous clinical signs recurred and the paraparesis continued to progress.
On initial neurologic examination, the cat was judged as having appropriate mentation and was ambulatory, with moderate paraparesis and a plantigrade posture in each pelvic limb. Conscious proprioceptive placing was lacking in both pelvic limbs. Patellar reflexes were considered hyperreflexive, consistent with an upper motor neuron lesion. Moderate hyperesthesia was elicited on focal palpation of the thoracolumbar junction. Results of cranial nerve examination and thoracic limb examination were unremarkable. Considered together, findings were consistent with T3-L3 myelopathy, and differential diagnoses included neoplasia (primarily lymphoma), feline infectious peritonitis, immune-mediated inflammatory disease, or intervertebral disk herniation.
A CBC, serum biochemical analysis, thoracic radiography, and abdominal ultrasonography were recommended as initial diagnostic tests, followed by advanced spinal imaging if no cause for the paresis could be identified. Clinicopathologic findings included a mild normocytic, normochromic, nonregenerative anemia (RBC count, 7.08 × 106/μL; reference range, 7.12 × 106/μL to 11.46 × 106/μL); mild hypocholesterolemia (serum cholesterol concentration, 77 mg/dL; reference range, 91 to 305 mg/dL); and mild hypophosphatemia (serum phosphorus concentration, 2.7 mg/dL; reference range, 2.9 to 6.3 mg/dL). Test results for FeLV and FIV infection were negative. Findings on thoracic radiography and abdominal ultrasonography were unremarkable.
The cat was anesthetized for MRI examination of the thoracolumbar portion of the spinal cord with a 1.5-T scanner.a The MRI protocol included multiplanar T2-weighted FRFSE, short tau inversion recovery, and pre- and postcontrast T1-weighted FSE sequences. A fusiform right-lateralized extradural mass measuring approximately 2.5 cm in length and 0.6 cm in width was identified in the neural canal at L2 (Figure 1). The mass appeared to be causing compression and leftward spinal cord displacement and occupied approximately 80% of the neural canal. The mass was well circumscribed and largely hypointense to the spinal cord on T2-weighted FRFSE and T1-weighted FSE sequences, with small areas of hyperintensity at its caudal aspect. It was contiguous with L2, extending into the vertebral pedicle and left side of the vertebral body. Moderate heterogeneous contrast enhancement of the soft tissue and vertebra portions of the mass was evident.
Given the MRI findings, surgery was recommended to alleviate the focal spinal cord compression and obtain biopsy samples for establishment of a histologic diagnosis. Differential diagnoses for the mass at that time included a tumor of primary bone origin (ie, osteosarcoma), although round cell neoplasia (ie, lymphosarcoma) was still given high consideration because of its common diagnosis in cats. Alternative treatment options, including radiation therapy alone or palliative care with continued medical treatment, were also discussed with the owner. The owner elected to proceed with surgical decompression.
Surgical decompression was performed via a right-sided hemilaminectomy from L1 through L3. The pedicle of L2 appeared abnormally thickened, and on entry to the neural canal, a large amount of proliferative tissue was visible ventrally, displacing the spinal cord. Grossly abnormal tissue was debulked until the spinal cord resumed a normal position within the neural canal. Several biopsy samples of the mass were obtained and submitted in formalin for histologic examination. Routine surgical closure was performed, and the cat recovered unremarkably from anesthesia.
Postoperative analgesia was provided as a continuous rate infusion of fentanyl (3 μg/kg/h [1.4 μg/lb/h], IV) overnight. The following morning, fentanyl administration was discontinued and oral transmucosal buprenorphine hydrochloride administration (0.02 mg/kg [0.01 mg/lb], q 8 h for 7 days) was initiated along with oral prednisolone administration (0.5 mg/kg [0.23 mg/lb], PO, q 12 h). The dosage of prednisolone was tapered over several weeks and then discontinued. Neurologic examination the morning after surgery revealed that the cat was nonambulatory, with good motor function in the left pelvic limb and minimal motor function in the right pelvic limb.
Histologic examination of the biopsy samples revealed extensive proliferations of redundant small-caliber blood-filled vessels of variable subtypes, including high numbers of capillaries and lesser numbers of small arterioles and venules, coursing through and widely separating the preexisting bony trabeculae. These vessels were lined by small, uniform endothelial cells and peripherally supported by pericyte-like cells or fibroblasts in some fields (Figure 2). Mild anisocytosis and anisokaryosis were present with no mitotic figures identified in 10 hpf (2.37 mm2). This benign vascular proliferation was diagnosed as vertebral angiomatosis of L2. These abnormal vascular proliferations extended to the margins of all biopsy samples.
Although vertebral angiomatosis is a benign vasculoproliferative disorder,1–3 clinical recurrence remained a concern because of the marginal nature of the surgical decompression. Adjuvant radiation therapy for additional local disease control was discussed with the owner, and both the beneficial and potential adverse effects were thoroughly explained. After consultation with a board-certified veterinary radiation oncologist, the owner elected to proceed with radiation therapy.
Radiation treatment was initiated 3 weeks after surgery. A radiation dose of 48 Gy was administered in 16 fractions of 3 Gy each over a 3-week period by use of 6-MV photons from a linear accelerator.b The cat remained hospitalized for much of the radiation treatment period, and no complications were noted during that period.
Clinically, strength improved in both pelvic limbs during the perioperative period. Rehabilitative therapy was recommended to assist with neurologic recovery. During the 3-week period of radiation treatment, the cat concurrently received rehabilitative treatment consisting of pelvic limb therapeutic massage and passive range-of-motion exercises, weight-shifting activities, assisted walking on a treadmill, and stepping over cavalettis, all under the guidance of a certified canine rehabilitation practitioner. When radiation therapy concluded, the cat was ambulatory with moderate monoparesis of the right pelvic limb. The owner continued therapeutic exercises at home.
Follow-up examination was performed 1 month after radiation therapy had ended. Physical examination revealed that the cat was in good health with no appreciable adverse effects of radiation therapy. Neurologic examination results at that time characterized the cat as fully ambulatory with only mild monoparesis of the right pelvic limb. No signs of spinal pain were noted, and the cat required no medications at that time. Additional follow-up examinations were performed every 3 months up to 1 year after surgery. At the 12-month examination, the owner reported no signs of paresis in the cat, which was described as highly active at home (typical ambulatory and jumping ability). Only a slight residual right pelvic limb monoparesis was found on neurologic examination.
Long-term follow-up information was available through a neurologic and MRI examination performed 26 months after surgery. The cat had no evidence of clinical recurrence at that time, and the owner reported no concerns at home. The cat's quality of life was described as excellent. Neurologic examination revealed only a mild delay in postural reactions of the right pelvic limb and the same slight monoparesis as noted at the 12-month examination. Results of MRI confirmed no recurrence of the angiomatosis at L2 (Figure 3). The MRI protocol was similar to the one used at the time of the initial diagnosis, with the addition of a postcontrast T1-weighted fat suppression sequence. Other MRI findings at this time were mild leftward displacement of the spinal cord from L1 through L3 secondary to epidural fat accumulation. Minimal spinal cord compression was noted. The right-sided hemilaminectomy site was unremarkable in appearance. Adjacent to this site, non–contrast-enhanced osteoproliferative bone was identified, consistent with a benign reaction. No contrast enhancement was identified in the region of the previous angiomatosis lesion. A heterogeneous intramedullary T2-weighted hyperintensity was identified within the spinal cord, spanning T10 through L3, and was most severe at the site of the previous angiomatosis lesion. This finding was attributed to the previous radiation therapy.
Funding for follow-up MRI examination was provided by the MedVet Charitable Foundation.
The authors declare that there were no conflicts of interest with respect to the research, authorship, or publication of this report.
The authors thank Josh Warnemunde for assistance with image preparation.
Fast recovery fast spin echo
Fast spin echo
1.5-T GE Signa Echospeed Plus, GE Healthcare, Milwaukee, Wis.
Varian Clinac 2100C, Varian Medical Systems Inc, Palo Alto, Calif.
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