Neoplastic diseases in the spinal column and spinal cord can have a dramatic impact on an individual as well as on their family members and friends. The tumor or its management may directly or indirectly cause neurologic impairments that affect the physical, social, vocational, and emotional capabilities of the individual. The available treatment options for both primary and metastatic spine tumors have improved and brought with them improved patient survival. Knowledge of recent developments in diagnosis and therapies is therefore critical for the management of these patients.¹

Spinal tumors are classically grouped into three categories: extradural tumors, intradural extramedullary tumors, and intradural intramedullary tumors (Fig. 17–1). These tumors maybe primary or secondary to metastatic disease. Primary tumors account for a relatively small percentage of all spinal tumors and generally occupy the intradural spaces; in contrast, spinal tumors secondary to metastatic disease tend to be extradural.

Extradural tumors refer to lesions outside of the dura mater, in the vertebral bodies and neural arches. Primary extradural tumors arise from osteoblasts, chondrocytes, fibroblasts, and hematopoietic cells. These tumors are more commonly malignant than benign. Primary malignant extradural lesions include lymphoma, osteosarcoma, Ewing’s sarcoma, chondrosarcoma, chordoma, sacrococcygeal teratoma, malignant fibrous histiocytoma, solitary plasmacytoma, and fibrosarcoma. Benign lesions include vertebral hemangioma, which is most common, giant cell tumors, osteochondroma, osteoid osteoma, and osteoblastoma.²

Metastatic disease is far more common in the extradural space. Over 18,000 new cases are diagnosed each year, with up to 70% prevalence in patients with cancer. Lung, breast, and prostate cancers are the most common primary solid tumors that metastasize to the spine. Renal cell carcinoma, thyroid cancer, and colon cancer are also relatively common. Among hematologic tumors, non-Hodgkin’s lymphoma is the most common.^2,3

Depending on the underlying malignancy, 2% to 5% of patients will develop clinical signs and symptoms of epidural spinal cord compression (ESCC) during the course of their disease. In most cases (80%), ESCC results in patients with known history of malignancy. In 20% of patients, it is the first manifestation of underlying malignancy. This is particularly common in patients with lung cancer and hematologic malignancies. Patients with myeloma and prostate cancer have the highest risk of developing ESCC (7.9% and 7.2%, respectively). In the pediatric population, sarcoma and neuroblastoma are the most common malignancies resulting in ESCC.³ Symptomatic lesions are most often diagnosed in the thoracic region, presenting with incomplete paraplegia, though cadaveric studies have shown the most common site of tumor burden is in the lumbar spine.⁴

Primary intradural extramedullary tumors are located within the dura mater but outside the spinal cord parenchyma. They arise from peripheral nerves, nerve sheaths, and sympathetic ganglion. Extramedullary tumors are mostly benign and can be seen in all regions of the spine. These benign tumors include meningioma, schwannoma, neurofibroma, paraganglioma, and ganglioneuroma. In adults more than 75% of extramedullary tumors arise from the nerve sheath, whereas in the pediatric population 85% are ganglion in origin. Malignant primary extramedullary tumors are rare, but include malignant nerve sheath tumors and hemangiopericytoma.²

Extramedullary metastases, or leptomeningeal disease (LMD), are a relatively common complication of cancer, occurring in 3% to 8% of all patients. Primary tumors that commonly cause leptomeningeal disease include brain tumors, particularly glioblastoma, central nervous system (CNS) lymphoma, lymphoreticular tumors such as leukemia and lymphoma, breast cancer, lung cancer, and melanoma. The percentage of primary brain tumors associated with leptomeningeal metastases is 23%, leading to the belief that leptomeningeal disease develops as a manifestation of the end stage of the disease in primary brain tumor patients. The most common site of involvement is the dorsal aspect of the spinal cord, particularly in the cauda equina.²

Primary intradural intramedullary tumors are relatively rare, accounting for 4% to 5% of all primary central nervous system tumors. These tumors are located within the spinal cord parenchyma and arise from glial cells, neuronal cells, and other connective tissue cells. Fifty-six percent of primary intramedullary tumors are benign.⁴ Ependymomas and astrocytomas represent the majority of primary spinal cord tumors. Ependymomas are the most common intramedullary tumor in adults (15% of cases) and are most often located in the filum terminale and conus medullaris. Astrocytomas comprise 6% to 8% of tumors, are the most common tumor in children, and can be located in any region of the spinal cord. Other primary intramedullary tumors include hemangioblastoma, cavernous angioma, ganglioglioma, neurocytic tumors, oligodendroglioma, and embryonal neoplasms.²

Intramedullary spinal cord metastases (ISCM) are rare, diagnosed in less than 1% of patients with cancer. Prior to the availability of MRI, the diagnosis was frequently missed or made only at the time of autopsy. ISCM has been detected in 2% of autopsies in cancer patients. It is rarely the first manifestation of systemic malignancy and usually occurs in the setting of extensive metastatic disease. Primary cancers that cause ISCM are lung and breast cancers, melanoma, lymphoma, and renal cell carcinoma. Half of all instances are the result of small cell lung cancer. A majority of patients with intramedullary lesions have concomitant brain metastases, and up to one-quarter have leptomeningeal disease.³

Intramedullary metastases can be seen throughout the spinal cord, usually as a solitary lesion. The most common segment involved is the vascular-rich cervical spinal cord; conus medullaris involvement is least common.²

Spinal tumors can be primary or secondary to metastatic disease and can occur in any region of the spinal column or spinal cord.

Primary extradural tumors arise from cells in the vertebral body such as osteoblasts, chondrocytes, fibroblasts, and hematopoietic cells. The majority of extradural metastases occur through hematogenous spread via venous or arterial routes. These hematogenous lesions are seeded in the basivertebral plexus and result in destruction of the posterior half of the vertebral body first. Osseous destruction then progresses to involve the pedicle and anterior vertebral body.³ Direct extension of primary tumors may also lead to metastases in the spinal column. For instance, prostate, bladder, and colorectal cancers may become locally aggressive and invade the lumbar or sacral space.⁵

Both primary and metastatic lesions may be osteolytic, osteoblastic, or mixed. Osteolytic lesions are more common in adults and are seen with breast, lung, and thyroid cancers. These lesions result in bone destruction greater than bone formation, whereas osteoblastic lesions result in bone deposition without breakdown of old bone first. Both osteolytic lesions and osteoblastic lesions alter normal bone architecture, increasing risk of fractures. Osteoblastic lesions typically occur with prostate and bladder cancer and carcinoid tumors. Mixed lytic/blastic lesions can be seen with lung, breast, cervical, and ovarian cancers.²

Both lytic and blastic lesions can result in deformity or collapse of the affected vertebral body leading to spinal instability by increasing strain on the support and stability elements of the spine including muscles, tendons, ligaments, and joint capsules.⁵ This bony instability may result in retropulsion of bony fragments into the epidural space resulting in spinal cord compression.⁴

Extradural lesions (Fig. 17–2) may also grow into the epidural space resulting in spinal cord compression. ESCC results in mechanical injury to axons and myelin as well as vascular compromise of the spinal arteries and epidural venous plexus. This vascular compromise may result in cord ischemia and/or infarction.³

Primary intradural extramedullary tumors (Fig. 17–3) arise from peripheral nerves, nerve sheaths, and sympathetic ganglion. Metastatic disease is thought to reach the leptomeninges by direct extension from a parenchymal or dural metastasis adjacent to the subarachnoid or ventricular surface either spontaneously or as a by-product of surgical intervention or spread from the venous system via leptomeningeal veins. Alternatively, tumor cells within the bone marrow in the skull or vertebral bodies can grow along veins. Finally perineural extension from spinal nerves can occur, particularly from paravertebral metastases. The most common site of involvement is the dorsal aspect of the spinal cord, particularly in the cauda equina.⁶

Primary intramedullary tumors (Fig. 17–4) arise from glial cells, neuronal cells, and other connective tissue cells. Metastatic lesions reach the intramedullary compartment either by hematogenous spread or via the leptomeninges, along nerve roots or through the Virchow-Robin spaces.³

Paraneoplastic syndromes are secondary to autoimmune responses to a primary tumor at a different site. By far the most common to affect the central nervous system is paraneoplastic encephalomyelitis, which can manifest as limbic encephalitis, brainstem encephalitis, myelitis, subacute sensory neuronopathy, or a combination of these. The usual etiology is small cell lung cancer.³ Finally, spinal metastasis to the vertebral body itself will appear hyperintense on a T1-weighted MRI scan, due primarily in part to the tumor replacement of bone marrow (Fig. 17–5).

Pain is the most common initial symptom in patients with epidural spinal cord compression (80% to 90%) and may precede the development of other neurologic symptoms by weeks to months. Pain related to spinal metastases may be the initial symptom of systemic disease in 10% of cancer patients. Three classically defined types of pain in the setting of extradural involvement are local, mechanical, and radicular pain.⁵

Localized pain is thought to be the result of periosteal stretching and inflammation caused by tumor growth. It is described as a deep “gnawing” or “aching” pain. It is often nocturnal, worsened by lying supine, and improves with activity and antiinflammatory or corticosteroid medications. Percussion or palpation over the spinous processes may elicit tenderness in patients with this type of pain.⁵

Unlike localized pain, mechanical pain is often refractory to antiinflammatory and pain medications, and varies with position or activity. This pain is indicative of impending or established spinal instability. Mechanical pain characteristically occurs with transitional movements or axial loading of the spine. Alternatively, this pain may be elicited by lying prone or supine, particularly in the thoracic spine. Mechanical pain responds well to stabilization of the spine with bracing or surgical fixation.^3,5

Radicular pain occurs in the setting of nerve root compression directly from tumor extension into the neuroforamen, or with pathological fractures that obliterate this space. This type of pain is often described as sharp, shooting, or stabbing in nature. In the thoracic region, radicular pain is typically bilateral and described as a tight band around the chest or abdomen. In cervical or lumbar lesions, it is usually unilateral, radiating to the upper or lower extremity, respectively.^3,5

An individual with epidural involvement may be affected by only one of these types of pain or by various combinations of these entities. Distinguishing the type of pain is a pivotal part of the evaluation process.

Motor weakness is the next most common symptom of ESCC, and is present in 35% to 85% of patients with metastatic disease at time of presentation. This weakness may be upper motor neuron, lower motor neuron, or a combination of both depending on the area of the cord involved. Patients with cervical involvement may have lower motor neuron weakness in the upper extremities and upper motor neuron weakness in the lower extremities. Thoracic lesions may result in upper motor neuron findings in the lower extremities, with flexor musculature weaker than extensor. Lumbosacral involvement often presents with a lower motor neuron pattern secondary to injury at the level of the cauda equina.⁵