Spine: neoplasia

• Origin: Spinal neoplasia can be either: primary, result from extension of a neoplastic process into the spinal canal or can occur through metastasis of tumor from a distant location.
• Classification: Tumors involving spine and spinal cord can be classified as to location of tumor relative to dura and spinal cord parenchyma. They can arise in extradural, intradural/extramedullary or intramedullary spaces.
• Extradural tumors: Most common and include primary and secondary bone tumors (osteosarcoma, fibrosarcoma, chondrosarcoma), hemangiosarcoma, various carcinomas, multiple myeloma and other plasma cell tumors and lipomas, liposarcomas and lymphosarcomas. Epidural lymphosarcoma is a common spinal tumor in cats.
• Tumors arising in the intradural but extramedullary location: Include nerve sheath tumors and meningiomas.
• Tumors arising within the spinal cord parenchyma: Include astrocytomas, ependymomas and oligodendrogliomas.

• Any animal can be affected with a spinal tumor.
• Most common in animals 5 years of age plus.
• Some instances in animals less than one year old.
• Animals with tumors involving spine or spinal cord present with clinical signs reflective of level of lesion involvement.
• Common clinical signs include spinal pain and varying degrees of limb dysfunction.

• Tumors affecting spine can result in an acute onset of clinical signs.
• May be due to sudden alterations in spinal cord blood flow (ischemia) or rapid evolution of spinal cord edema.

• Animals with spinal tumors are usually older than 5 years of age, however exceptions exist.
• Spinal cord blastoma reported in dogs less than 1 year of age.
• Spinal lymphoma can also occur in young cats.

• All breeds of dogs and cats can be affected.
• Certain breeds of dogs, such as young German Shepherd dogs German Shepherd Dog with spinal cord blastoma (nephroblastoma), can be affected with specific tumor types (tumor referred to historically as neuroepithelioma).

• Diagnosis of spinal tumors ranges (US) from $500 to $1,200 depending upon diagnostic test utilized.
• Surgical treatment may cost (US) between $2,000 and $4,000.
• Chemotherapy and radiation therapies may cost (US) from $500 to $5,000 depending on treatment protocols.

• Anesthestic risks vary with systemic health of animal.
• No inherent anesthestic risks occur with spinal tumors unless location affects vital functions ie breathing.

• Spinal neoplasia can:
  • Be primary.
  • Result from extension of a neoplastic process into spinal canal.
  • Occur through metastasis of tumor from a distant location. Cell of origin will determine tumor type.
• Extradural tumors are most common and include:
  • Primary and secondary bone tumors (osteosarcoma Osteosarcoma , fibrosarcoma Fibrosarcoma , chondrosarcoma Chondrosarcoma ).
  • Hemangiosarcoma Hemangiosarcoma.
  • Various carcinomas.
  • Multiple myeloma Myeloma and other plasma cell tumors.
  • Lipomas, liposarcomas, and lymphosarcoma Lymphoma.
• Epidural lymphosarcoma is a common spinal tumor in cats.
• Tumors arising in the intradural but extramedullary location include:
  • Nerve sheath tumors Nerve sheath: neoplasia.
  • Meningiomas Meningioma.
• Tumors arising within the spinal cord parenchyma  include:
  • Astrocytomas Brain: neoplasia.
  • Ependymomas Brain: ependymoma.
  • Oligodendrogliomas.

• Clinical signs of a spinal tumor may occur acutely or be prolonged over weeks to months.

• Clinical signs depend upon the level of spinal cord involvement.
• Animals with spinal lesions usually display varying degree of pain or limb dysfunction.
• The extradural and intradural extramedullary tumors usually cause pain, whereas the intramedullary tumors are usually non painful.

• Lesions in the cervical region may affect all limbs.
• Tumors of the C6-T2 segments may be associated with ipsilateral Horner's syndrome Horner's syndrome or ipsilateral loss of cutaneous trunci contraction.
• Chronic thoracic limb lameness is common with tumors of the brachial plexus.
• Lesions of thoracolumbar segments may result in:
  • Dysfunction of pelvic limbs.
  • Urination.
  • Defecation.
  • Tail movement.

• Magnetic resonance (MR) imaging Magnetic resonance imaging: basic principles is superior to both myelography and CT in providing anatomical information with spinal tumors .
• Magnetic resonance imaging often shows pathophysiologic consequences of neoplasia (eg edema) better than other imaging modalities. .

• Diagnosis of spinal tumor can be made with myelography or computed tomography (CT).
• Spinal tumors may compress or expand the spinal cord. Classically, an expansion and outlining of the lesion referred to as a "golf-tee" sign is found with intradural but extramedullary lesions  .
• Nerve sheath tumors will expand either side of where nerve traverses dura, giving tumors a "dumb-bell-shaped" appearance. Expansion of dural tube in 90° opposed radiographic views (such as lateral and ventrodorsal projection) is indicative of an intramedullary lesion.

• Tumors of bone may be evident on survey radiographs as osteolytic/osteoproliferative processes.
• These bony changes need to be differentiated from diskospondylitis Diskospondylitis and vertebral bony osteomyeltis Osteomyelitis.
• Classically, vertebral tumors do not cross the joint space (intervertebral disk).
• Rarely, however, vertebral tumors invade adjacent vertebral bodies.
• Extradural compression of spinal cord overlying vertebral body rather than intervertebral disk space is indicative of neoplasia.
• Nerve sheath tumor or meningioma is often centered on nerve roots within intervertebral foramina. Foramen where abnormal nerve exits may be enlarged.

Definitive diagnostic features

• Definitive diagnosis requires cytologic or histologic evaluation.
• Samples may be collected via aspiration for cytology or at surgery for biopsy .

• Spinal neoplasia can:
  • Be primary.
  • Result from extension of a neoplastic process into spinal canal.
  • Occur through metastasis of tumor from a distant location.
• Tumors may be found in either:
  • Extradural region.
  • Intradural/extramedullary regions.
  • Intramedullary regions.
• Most commonly, extradural tumors involve vertebrae causing expansion or lysis of bone. These tumors include:
  • Osteosarcoma Osteosarcoma.
  • Fibrosarcoma Fibrosarcoma.
  • Chondrosarcoma Chondrosarcoma.
  • Hemangiosarcoma Hemangiosarcoma.
  • Various carcinomas.
  • Multiple myeloma Myeloma.
  • Other plasma cell tumors.
• Other soft tissue tumors of the epidural space include lipomas, liposarcomas and lymphosarcoma Lymphoma.
• Epidural lymphosarcoma is a common spinal tumor in cats.
• Tumors arising in the intradural but extramedually location include:
  • Nerve sheath tumors Nerve sheath: neoplasia.
  • Meningiomas Meningioma.
• With these tumors, dural tube is often enlarged and discolored. In instances of nerve sheath tumors, the peripheral nerves traversing the dura may be enlarged, firm and discolored (red-gray).
• Tumors arising within the spinal cord parenchyma include:
  • Astrocytomas Brain: neoplasia.
  • Ependymoma Brain: ependymoma.
  • Oligodendroglioma.
• These tumors result in an expanded spinal cord grossly and often are discolored on cross section.

• Vary depending upon tumor type.

• Numerous diseases can affect spinal cord Spinal cord diseases: overview and result in similar clinical signs.
• Most common diseases that result in spinal pain and limb dysfunction include:
  • Intervertebral disk disease Intervertebral disk: type 1 herniation Intervertebral disk: type 2 herniation.
  • Fracture.
  • Subluxation.
  • Diskspondylitis Diskospondylitis.
  • Myelitis.

• In addition, in the cervical area, other diseases may cause similar signs such as:
  • Cervical malformation/malarticulation (Wobbler's syndrome) .
  • Atlantoaxial instability Atlantoaxial joint: subluxation.

• Other diseases ie syringomyelia and hydromyelia may cause enlargement of the spinal cord similar to an intramedullary spinal tumor .

• Spinal neoplasia often requires definitive treatment for successful outcomes.
• If owners do not elect definitive treatment options, corticosteroids (prednisone Prednisolone ) may provide symptomatic improvement in clinical signs.
• If a vertebral segment is deemed unstable due to bony destruction, exercise restriction or confinement is necessary.
• External support braces and bandages may be helpful concurrently.
• Painful spinal diseases are treated most appropriately with narcotics (such as codeine Codeine 1-2 mg/kg PO q 4 to 6 h PRN; fentanyl patches Fentanyl (transdermal patch) ).
• Non-steroidal anti-inflammatory drugs may be helpful in some cases

• Treatment options include surgical removal and possibly, radiation therapy.
• Surgical removal is easiest with extradural tumors, however, intradural/extramedullary and intramedullary tumors have occasionally been successfully resected.
• Computed tomography and MRI are often helpful in localizing tumor extent prior to surgery .
• Prognosis depends upon:
  • Degree of resection.
  • Degree of spinal infiltration.
  • Associated spinal damage prior to and during surgery.
  • Tumor type.
• Two reviews of spinal tumors and peripheral nerve sheath tumors have been published (Levyet al1997; Brehmet al1995) - see below.
• Median survival in dogs with spinal tumors who had surgery varied depending upon whether the tumor was benign (median survival - 1,410 days) or malignant (median survival - 180 days).
• For nerve sheath tumors, prognosis was influenced by whether tumor was more peripheral in location versus involving nerve plexus or root (median survival plexus group - 360 days; median survival root group - 150 days).
• Conventional radiation therapy Radiotherapy is being used with increasing frequency in dogs with spinal tumors.
• Radiation therapy is more apt to control tumor progression, however, in some instances, may eradicate tumor completely.
• Significant and rapid reduction eg in spinal lymphoma, may occur following radiation therapy.
• Main goal of treatment is to administer highest possible dose to tumor while minimizing the dose to surrounding normal tissue.
• Overall, small numbers of animals with spinal tumors have been treated and radiation protocols vary:
  • Fractional dosing schemes have been used to decrease acute toxicity of the radiation.
  • Most coarse fractionation reported was 6 Gy fractions twice weekly over 3 weeks. Majority of dogs treated for brain masses were treated with 10-12 fractions, generally given 3 times weekly (Monday, Wednesday, and Friday) of approximately 4 Gy each, for a total dose of 48 Gy. All of the doses appeared to be generally well tolerated for periods studied. Some of the reports indicated neurologic and pathologic changes compatible with acute radiation induced necrosis of brain. Suggested that a fraction size of 3 Gy will reduce incidence of late responding tissue response. Recommended, therefore, that daily fractions of 3 Gy be given up to four weeks, with total normal tissue dose below 50-55 Gy.
• Side effects include radiation damage to normal structures surrounding abnormality. Both acute, early delayed and late delayed affects can be seen. Acute affects may be result of edema due to tumor kill and may be reversed with anti-edema medications. Later effects may not be reversible and may be as detrimental to the animals as underlying disease.
• Chemotherapies are infrequently used for primary spinal tumors. In some instances, similar chemotherapeutic agents as used for appendicular osteosarcoma Osteosarcoma: axial skeleton (cisplatin Cisplatin , carboplatin Carboplatin ) are used for vertebral osteosarcoma Osteosarcoma.
• Spinal or perispinal lymphoma may be responsive to similar chemotherapeutic agents as for systemic lymphoma. Because of the relatively good CSF penetration of cytosine arabinoside, this drug is often added to spinal lymphoma treatment protocols.

Refereed papers

• Recent references from PubMed and VetMedResource.
• Levy M S, Kapatkin A S, Patnaik A K, Mauldin G N & Mauldin G E (1997) Spinal tumors in 37 dogs: Clinical outcome and long-term survival (1987-1994). JAAHA 33 (4), 307-312 PubMed.
• Brehm D M, Vite C H, Steinberg H S, Haviland J & van Winkle T (1995) A retrospective evaluation of 51 cases of peripheral nerve sheath tumors in the dog. JAAHA 31 (4), 349-359 PubMed.
• McCarthy R J, Feeney D A & Lipowitz A J (1993) Preoperative diagnosis of tumors of the brachial plexus by use of computed tomography in three dogs. JAVMA 202 (2), 291-294 PubMed.

Other sources of information

• DeLahunta A (1983)Veterinary Neuroanatomy and Clinical Neurology.2nd edn. Philadelphia: W B Saunders.