Primary spinal cord tumor is less common than metastatic tumors. Tumors of the spinal canal in any location may be classified in three ways depending on the tissue compartment in which they are found:
Tumors arising within the lumbar spinal canal may involve either the vertebrae, the distal end of the spinal cord (conus medullaris), or the nerve roots (cauda equina). These tumors may be primary or metastatic, benign or malignant, and may have a broad range of presentations. The most common tumors involving the vertebrae are metastatic lesions with the most common location being the vertebral body. The most common tumors arising from the conus medullaris are ependymoma and astrocytoma. A metastatic lesion within the conus medullaris is possible but very uncommon. The most common tumor involving the cauda equina is a schwannoma. Patient’s will typically present with a combination of back pain, radiculopathy, or myelopathy. Treatment may involve surgical resection, radiation, and/or chemotherapy.
Tumors of the vertebrae are quite frequently metastatic with primary bone or cartilaginous tumors much less common. Metastatic lesions are typically from breast, prostate, lung, or kidney (although metastasis from any location is a possibility). Tumors within the conus medullaris may arise from the astrocytes of the spinal cord (astrocytoma) or the ependymal lining of the central canal of the spinal cord (ependymoma). Metastatic lesions are much less common. Tumors of the cauda equina typically arise from the Schwann cells lining the nerve roots (schwannoma).
Another tumor type that can be seen within the lumbar spinal canal is a meningioma. This benign lesion is an intradural extramedullary (ID/EM) tumor which may arise anywhere along the lumbar spinal canal causing compression of the nerve roots or the conus medullaris.
Approximately 55% of spinal lesions are ED and involve the vertebral column. Of these, 20% are located in the lumbar spine. The most common lesion is a metastasis with the most common location being the vertebral body. Approximately 40% of spinal lesions are ID/EM. These are generally meningiomas or schwannomas involving the nerve roots. Approximately 5% of spinal lesions are ID/EM. Greater than 90% are ependymoma or astrocytoma of varying histological grades. Only about 2% are a metastasis; these are specifically within the conus medullaris. However, ID/EM lesions are almost exclusively ependymoma.
Symptoms may arise from either compression of the neural elements or local tumor factors causing metabolic derangement within the neurons. Metastasis within the epidural space may grow and compress the cauda equina or conus medullaris. This may lead to a combination of upper and lower motor neuron findings and bowel/bladder incontinence. Involvement of the lumbar vertebrae may lead to back pain. The back pain may be a mechanical pain related to a pathologic fracture or instability, or the pain may be a biological pain related to local tumor factors. ID/EM tumors may compress the cauda equina causing radiculopathy or potentially grow large enough to compress the conus medullaris thus leading to myelopathy. Also, the lesion may compress the vasculature possibly causing venous hypertension or arterial ischemia thus leading to spinal cord edema and neuronal dysfunction. Intrinsic lesions of the conus medullaris cause compression of the spinal cord fibers as they grow and metastases release local tumor factors that cause spinal cord edema and metabolic derangement.
The typical presentation of ED lesions is back pain with a varying degree of neurological deficit related to compression of the neural elements. The patient with metastatic disease will give a history of weight loss, general malaise, night sweats, and a history of risk factors for cancer. The patient with an ID/EM lesion will also give a history of back pain with radicular and/or myelopathic symptoms depending on the level of compression (nerve roots or conus medullaris). The presentation of ID/IM lesions will involve varying degrees of back pain as well. The diagnosis may be delayed due to the slow onset of neurological symptoms (sometimes years). Patient’s may only complain of the slow onset of numbness or tingling in the extremities which can progress over some time. A varying degree of upper or lower motor neuron findings may also be present as well as bowel/bladder incontinence.
The evaluation of a patient with back pain without neurological deficit should be conservative as long as there are no significant risk factors, such as night sweats, or weight loss. However, should risk factors exist then an evaluation with either CT scan or MRI with contrast should be initiated. If the patient presents with a neurological deficit or bowel/bladder incontinence, then an MRI with contrast should be obtained to identify any possible mass lesion. In addition, if a mass lesion is identified, then an appropriate workup would include a CT scan of the chest, abdomen, and pelvis or a full body PET scan to evaluate for any primary malignancy. A multidisciplinary evaluation of the patient should then proceed with the neurosurgeon, oncologist, radiologist, and neurologist all participating.
The treatment of a patient with metastatic disease always should include systemic control of the disease if possible. Surgical indications are aimed at decompression of the neural elements, gross total tumor resection if possible, and stabilization of the spine should there be any instability. As always, a multidisciplinary approach is best to determine the appropriate treatment based on long term prognosis as well as other indicated systemic treatments. ID/EM lesions usually are benign. If schwannoma or meningioma is suspected and the patient is asymptomatic, then observation is usually appropriate if the lesion is small. However, should there be a large lesion or neurological symptoms, then surgical resection for decompression and gross total resection should be attempted. Radiation or chemotherapy options depend on the type and histological grade of the lesion resected. For ID/IM lesions, which are most commonly astrocytoma or ependymoma, initial surgical resection for decompression and gross total resection is recommended. The role of chemotherapy and radiation and the timing of such treatments is still controversial. However, the indications for radiation or chemotherapy do depend on tumor type, histological grade, and degree of resection. For ID/IM metastatic lesions the indications for surgery, radiation, and chemotherapy are more complex and depend heavily on a multidisciplinary approach.