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 Signs

  • 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