Spinal Cord Tumors

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