Veterinary Society of
Surgical Oncology

GENERAL CONSIDERATIONS

Location

  • spinal cord tumors are classified as extradural, intradural-extramedullary, or intramedullary
  • extradural tumors are most common and account for 50% of spinal tumors
  • intradural-extramedullary account for 30% and intramedullary account for 15% of spinal tumors
  • Signalment

  • 90% of spinal tumors occur in large breed dogs
  • 28% of spinal tumors occur in cats and dogs < 3 years
  • Feline Spinal Cord Tumors

    General Considerations

  • LSA is the most common tumor affecting the spinal cord in cats
  • other tumor types are rare but include:
  • extradural: vertebral OSA
  • intradural-extramedullary: meningioma
  • intramedullary: very rare but astrocytoma has been reported
  • intradural-extramedullary tumors account for > 50% of non-lymphoid tumors with the most common being meningioma, but nerve sheath tumors and LSA are also reported
  • Spinal Lymphosarcoma

  • extradural LSA (primary or secondary) is common in cats
  • median age 24 months
  • majority of cats with spinal LSA are FeLV positive
  • clinical signs are uncommon with only 11% showing neurologic dysfunction
  • spinal LSA is diagnosed in up to 21% of cats with LSA in 1 necropsy study
  • 96% (22/23) spinal LSA are solitary, bit spinal involvement with multicentric LSA is considered more common
  • spinal LSA has a predilection for the thoracic and lumbar spinal cord
  • CLINICAL FEATURES

    History

  • extradural spinal cord tumors are usually slow growing and progressive over weeks to months
  • acute onset of neurologic signs may be caused by tumor-induced hemorrhage or ischemia
  • intramedullary tumors have a more rapid growth rate and have a higher incidence of hemorrhage, ischemia, and necrosis
  • Clinical Features

  • clinical signs depend on the tumor location and are difficult to differentiate from other causes of myelopathy
  • extradural tumors may involve the meninges, spinal nerves, or nerve roots which results in varying levels of pain from discomfort to extreme spinal hyperesthesia
  • tumors involving the brachial or lumbar intumescence may cause lameness, limb elevation, neurogenic muscle atrophy, and depressed spinal reflexes
  • hyperesthesia is associated with extradural and intradural-extramedullary tumors, but not intramedullary tumors
  • fundus, lymph node, and rectal examination should be performed for evidence of LSA or metastatic lymphadenopathy
  • DIAGNOSIS

    Hematology

  • hematologic abnormalities in cats with spinal LSA are common (74%) and include anemia, leukopenia, thrombocytopenia, and circulating lymphoblasts
  • Bone Marrow Aspiration

  • bone marrow aspirates are also abnormal in cats with spinal LSA (81%)
  • Survey Radiographs

  • thoracic radiographs for evaluation of metastatic disease
  • radiographic findings include cortical lysis with collapse of the adjacent intervertebral disk space
  • vertebral body and dorsal lamina are more frequently affected than dorsal and transverse spinous processes
  • radiographic signs not always visible due to inconsistent vertebral shape, overlying ribs and soft tissue, and improper positioning
  • cortical bone destruction is a late event in metastatic vertebral lesions
  • radiographic abnormalities associated with non-vertebral spinal cord tumors are rare, but slow and progressive tumor growth may cause enlargement of an intervertebral foramen or vertebral canal with thinning of cortical bone
  • Cerebrospinal Fluid Analysis

  • CSF collection and analysis are recommended if survey radiographs are inconclusive
  • CSF is collected from a lumbar site and needle left in situ for myelography
  • CSF changes include increased protein content and normal to increased white cell count
  • CSF findings with LSA include increase white cell count with abnormal lymphocytes
  • abnormal CSF findings are more common in dogs with spinal LSA due to leptomeningeal involvement
  • Myelography

  • indications: determining presence, anatomical location and dural site of spinal cord tumor
  • spinal cord tumors are classified as extradural, intradural-extramedullary, or intramedullary
  • classification may be difficult due to spinal cord edema
  • Advanced Imaging

  • CT is recommended for vertebral tumors due to excellent bone detail
  • however, myelography is superior to CT in differentiating intramedullary from intradural-extramedullary
  • MRI is recommended for spinal cord tumors due to excellent soft tissue detail
  • MRI provides accurate information on anatomic location and bone involvement, but differentiation between intradural, extradural and intramedullary, and extramedullary difficult
  • TREATMENT

    General Considerations

  • management options depends on tumor location, extent, and histologic type
  • aim: alleviate spinal cord compression
  • treatment options include conservative (with corticosteroids) and surgery
  • surgery allows decompression ± complete removal or cytoreduction of the mass
  • surgical decompression techniques include hemilaminectomy and dorsal laminectomy
  • complete resection of spinal meningioma is complicated by adhesions to the pia mater or spinal cord, and friable texture resulting in piecemeal dissection
  • rhizotomy can be performed to facilitate tumor resection, but avoided in the brachial and lumbar intumescence
  • radiation therapy can be used for LSA, incompletely resected spinal tumors, and when surgery is not feasible
  • spinal cord is resistant to the acute effects of radiation due to low replication rate, but late effects (> 2 years) can be seen due to progressive demyelination and malacia of white matter (especially oligodendrocytes, endothelial cells, astrocytes, and microglial cells)
  • radiation therapy and chemotherapy are recommended for cats with spinal LSA
  • PROGNOSIS

    General Considerations

  • prognosis depends on resectability, histologic type, location, and severity of neurologic signs
  • poor prognosis for metastatic and vertebral tumors
  • Cats

  • prognosis for cats with spinal tumors is better for non-lymphoid tumors than spinal LSA
  • MST 180 day for cats with surgically resected meningioma
  • MST 3-125 days for cats with spinal LSA, with all survival times < 5 months for cats with spinal LSA
  • 50% CR with chemotherapy for cats with spinal LSA (with 14 week median duration of remission)
  • MST 125 days with chemotherapy and radiation therapy
  • MST 81 days with surgery and corticosteroids
  • MST 34 days with corticosteroids
  • MST 3 days with chemotherapy
  • SPINAL CORD TUMORS

       
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