Osteochondroma

These lesions are the most common benign bone tumors, encompassing approximately 35% of all nonmalignant osseous tumors. These tumors arise from the cartilaginous end plates and are slow-growing tumors.^19,20 The majority are asymptomatic lumbar spine lesions found on incidental radiographs. Symptomatic patients commonly present with dull backache, decreased motion, or, rarely, deformity. Plain radiographs demonstrate a protruding lesion with well-demarcated borders in the dorsal elements. On rare occasions, pain, neurologic deficit, or an accelerated growth pattern may be related to malignant transformation.

Osteoid Osteoma and Osteoblastoma

These two tumor types share a common pathologic origin but differ in size and incidence of spine involvement. Both tumors most commonly present in patients less than 30 years of age. Osteoid osteomas are smaller than osteoblastomas (≤2 cm vs. >2 cm). Osteoid osteomas are most commonly located in the lumbar spine and account for 2.6% of all excised primary bone tumors and up to 18% of axial lesions. Osteoblastomas are less common and represent fewer than 3% of benign bone tumors.

Patients with osteoid osteomas commonly present with a dull ache that is exacerbated at night. This condition is believed to be the result of prostaglandin production by the tumor; thus, the classic pain relief with aspirin. Neurologic deficits are rare. Osteoblastomas are more likely to result in spinal deformity and neurologic sequelae, including torticollis in 13% of cervical lesions. Plain films are pathognomonic, revealing a small radiolucent nidus with surrounding sclerosis usually located in the dorsal elements.^21,22

Giant Cell Tumor

Unlike the majority of primary bone tumors, giant cell tumors occur more commonly in patients in their 30s. The most common presentation is that of pain. However, disease advancement may result in bowel or bladder dysfunction. These aggressive tumors carry some malignant potential and a high incidence of local recurrence. They are responsible for approximately 10% of all primary benign bone tumors and affect the spinal axis in approximately 10% of all cases. These lesions may occur in conjunction with aneurysmal bone cysts (3% to 6%).^23,24 They most commonly occur in the sacral region when the spinal column is involved. Plain radiographs demonstrate cortical expansion with little reactive sclerosis or periosteal reaction.^23,24 Both T1- and T2-weighted MRI scans reveal homogeneous signals, whereas presurgical CT studies can better delineate the degree of vertebral bone involvement. Because of the nondistinct characteristics of giant cell tumors, radiographic investigation, coupled with intraoperative histology, is important to separate this condition from other primary bone tumors.

Aneurysmal Bone Cyst

Although responsible for only approximately 1% to 2% of all primary bone tumors, aneurysmal bone cysts affect the axial skeleton in 12% to 25% of reported cases of aneurysmal bone cysts.²⁴ They occur more frequently in the thoracolumbar region and dorsal elements in females and patients younger than 20 years of age. Multiple vertebral involvement occurs in 40% of cases. Radiographs demonstrate a single osteolytic lesion with a thin, well-demarcated cortical rim.

Hemangioma

Hemangiomas are found in 11% of general autopsies,^25,26 but symptomatic spinal hemangiomas are exceedingly rare. The most common initial symptom in the case of a solitary lesion is back pain, with or without radiation into the lower extremities.^25,26 These lesions are characterized by slow growth and a female predominance.

Eosinophilic Granuloma

Eosinophilic granuloma is the solitary osseous lesion version of a group of disorders characterized by an abnormal proliferation of Langerhans cells. In its disseminated forms, it is designated Letterer-Siwe disease and Hand-Schüller-Christian disease. The overall incidence for any variety of the histiocytosis X spectrum is one per million people, and it most commonly occurs in patients younger than 20 years of age. Clinical presentation most commonly involves pain in the thoracolumbar region. MRI is the investigative procedure of choice, with definitive diagnosis through biopsy.²⁷

Chondrosarcoma

This malignant cartilage-forming primary bone tumor is an uncommon spinal neoplasm. It is more common in adults, in whom it less commonly involves the spine.²⁸ There is an even distribution of tumor involvement among cervical, thoracic, and lumbar locations.²⁵ Chondrosarcomas may arise as a primary lesion or secondary to irradiation of lesions, including Paget disease or osteochondroma.²⁹ The most common presentation is pain (50%) and localized swelling (30%). There is a linear relationship between degree of pain on presentation; a larger, more aggressive tumor; and decreased time of survival.^30,31 Diagnosis is usually based on radiographic studies that reveal bone destruction, a soft tissue mass, and “fluffy” calcifications and pathology from resection.^30,31

Osteogenic Sarcoma and Ewing Sarcoma

Both osteogenic sarcoma and Ewing sarcoma represent uncommon malignant lesions of the spinal column, with a combined incidence of less than 4% of spinal column tumors.^32–34 Most cases of Ewing sarcoma and primary osteogenic sarcoma (50%) present in the first 20 years of life. Secondary sarcomas arise in the fifth to sixth decades as a result of irradiated bone or a preexisting pagetoid lesion. Almost 70% of clinical presentations are accompanied by a neurologic deficit secondary to epidural compression.^32–34 The most common presentation of Ewing sarcoma is pain.

Chordoma

Chordomas are tumors of the axial skeleton and the skull base arising from the primitive notochord. They encompass approximately 1.4% of all skeletal sarcomas. Although chordomas are histologically low-grade lesions, they are locally invasive tumors, and metastases may occur in 5% to 43% of cases.^35–37 More than 50% of these lesions are located in the lumbosacral region, 35% are located in the clival and cervical area, and the remainder are spread throughout the rest of the vertebral column.³⁷ Neurologic deficit is usually found in the form of bowel/bladder dysfunction or, less frequently, cauda equina symptoms (20%).³⁷ Combined imaging, using MRI and CT, provides an evaluation of the tumor and its soft tissue and bony involvement.

Multiple Myeloma

Multiple myeloma and solitary plasmacytoma account for 45% of all malignant bone tumors.³⁸ These disorders are the result of abnormal proliferation of plasma cells, which are responsible for immunoglobulin and antibody production and affect the spine in 30% to 50% of reported cases. Multiple myeloma is primarily a disease of the sixth and seventh decades of life and has a predilection for the thoracic spine (50% to 60%).

Patients present with back pain in approximately 75% of cases.³⁸ Unlike the classic metastatic disease presentation of pain with recumbency, multiple myeloma is sometimes relieved by rest and aggravated by mechanical agitation that mimics other sciatic or neurogenic sources. Systemic complications include hyperalbuminemia, renal insufficiency, nephrolithiasis, and characteristic serum protein abnormalities. Plain radiographs and CT can be diagnostic because of the characteristic osteolytic picture without sclerotic edges that involve the ventral portion of the vertebral body and usually spare the dorsal elements.

Lymphoma

Hodgkin disease is a malignant disease of the reticuloendothelial system. Spine involvement occurs in approximately 10% of all extranodal lymphomas.^39,40 Spine osseous involvement occurs at a decreasing frequency as one ascends the spine from the lumbar, thoracic, and, uncommonly, cervical regions. Age at presentation is bimodal, with those ages 15 to 35 and those older than age 50 most frequently affected. Clinical presentation involves concurrent constitutional signs and symptoms of fever and night sweats, and acute cord compression and epidural compression are not uncommon.^39,40

Metastatic Disease

Metastatic disease in the form of distant foci is evident at autopsy in 40% to 85% of cases of malignancy.⁴¹ The spine is the most common site of skeletal metastasis, and at least 5% of patients with malignancies suffer from this condition.^41,42 The axial skeleton is the leading site of bone metastases that are caused by hematogenous spread through the rich venous network that drains the lungs, pelvis, and thorax. Breast, lung, prostate, and thyroid malignancies account for 50% to 60% of metastatic lesions.⁴¹ Overall, epidural metastases are equally spread throughout the thoracic and lumbosacral spine, but symptomatic metastases occur most commonly in the thoracic spine. Nearly all patients initially complain of back pain, followed by weakness and ataxia. At the time of diagnosis, more than 50% of patients will have a paraparesis or bladder/bowel disturbance.^41,43

Diagnostic regimens include laboratory studies demonstrating an elevated calcium level, prostate-specific antigen, or alkaline phosphatase. The ultimate diagnosis relies on radiographic studies, including plain radiographs. Bone scans are warranted for suspected occult lesions because approximately 30% to 50% of the trabeculated bone in a vertebral body must be destroyed before the lesions can be detected on plain radiography. Other radiographic modalities, including MRI and CT/myelography and positron emission tomography (PET) scans, are helpful in determining the extent of bone destruction, epidural compression, and disease spread. A metastatic workup, including both a plain chest radiograph and an enhanced abdominal/chest CT, determines the primary focus in the majority of cases. Pathologic confirmation may be made via biopsy of a primary malignant focus or via biopsy or resection of the spinal lesion.

Spinal Cord Tumors

The majority of lesions that involve the spinal cord and meninges occur in the epidural space in the form of metastatic disease. The largest group of neoplastic spinal lesions that involve the spinal cord and meninges occurs in the intradural-extramedullary space (40–50%), followed by the extradural space (30%) and the intramedullary space (20–25%).^43,44

Back pain is the most common initial complaint in the adult population that harbors spinal neoplasms; the pediatric population with spinal tumors tends to present with neurologic deficit in the form of motor or gait disturbances. The back pain in the adult population is usually diffuse and unrelated to activity, thus prolonging diagnosis until the pain becomes radicular or symptoms that are caused by cord or root compression ensue.

Extradural Lesions

Symptoms may be caused by compression, invasion, or irritation of the involved anatomy. The majority of epidural lesions discussed earlier in the chapter are metastatic in origin. Other epidural pathologies include lipomatous masses, hematomas, and vascular malformations.

Intradural-Extramedullary Lesions

Meningiomas, schwannomas, and neurofibromas constitute more than 50% of all neoplastic processes in the intradural-extramedullary space. Nittner’s review of 4885 adults with spinal cord tumors found schwannomas (23%) and meningiomas (22%) to be the most common lesions of the intradural-extramedullary space.^45,46 Symptoms may be nocturnal and most commonly involve pain caused by root irritation. Early neurologic compromise is uncommon because of the adaptive compressibility of surrounding fat, CSF, and adjacent vascular structures. Neurologic compromise occurs when the compliance of surrounding structures is at its nadir and extradural compression is directly transmitted to the spinal cord.

More than 80% of meningiomas are located in the thoracic region, and they occur at a 4:1 ratio in women compared to men. Meningiomas can present with pain from a compressed nerve root as it exits the neural foramina. Although less common in the cervical and lumbar spine, large, slow-growing meningiomas may produce myelopathic symptoms from spinal cord compression, especially at the craniocervical junction.⁴⁷ Meningiomas are the most common benign tumor at the foramen magnum.^48,49 CT myelogram and MRI are the best investigative modalities.

Although both meningiomas and nerve sheath tumors are benign lesions that are usually found in thoracic dorsal sites, neurofibromas are a common finding in phakomatoses. Because neurofibromas are almost always lesions of the dorsal roots, patients commonly present with radicular symptoms.^50–52 Although their malignancy potential is low, nerve sheath tumors may be locally destructive if allowed to progress. Caudally located neurofibromas may displace adjacent nerve roots with possible bone erosion of nearby foramina as the neoplasm grows.

Schwannomas, which are commonly found with von Recklinghausen neurofibromatosis, are usually solitary lesions found in thoracic sites in adults between 40 and 50 years of age. These tumors are most commonly found in the intradural-extramedullary space; however, approximately 20% will be found crossing the dura or will be solely extradural. On clinical presentation, patients with these tumors exhibit radicular symptoms, and the tumor is typically easily diagnosed with MRI.

The remaining 30% of intradural-extramedullary tumors include sarcomas, dermoids, epidermoids, arachnoid cysts, teratomas, ganglion cysts, and, rarely, spinal metastases.^53,54 These lesions have characteristic features on MRI that help to delineate them. Arachnoiditis that presents with diffuse constant pain and associated paresthesias is the result of multiple operations on the back or clumping of nerve roots after the administration of the myelographic dye. The diagnosis is made via MRI or myelogram with visualization of characteristic nerve root clumping.