Tumors of the Cervical Spine

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32 Tumors of the Cervical Spine

Oren N. Gottfried, Scott L. Parker, Ziya L. Gokaslan

KEY POINTS

• Spine tumors are divided into those occupying the intramedullary, intradural-extramedullary, and extradural regions.
• In adults, ependymomas are the most common cervical intramedullary tumor; the optimal treatment is a complete resection.
• Cervical schwannomas are usually located intradurally. They are approached by laminectomy, with a high rate of total resection; however, large tumors or those with a large extradural component often require additional surgical exposure.
• The most common epidural spine disease is metastasis, for which the best treatment is circumferential decompression of the spinal cord, reconstruction, and immediate stabilization, plus postoperative radiotherapy.
• Malignant primary spinal tumors are more common in adults. Chordoma is the most common solid primary tumor; it is locally aggressive, often involves the cervical region when it occurs in the mobile spine, and is best managed by a total resection.

Introduction

Tumors of the vertebral axis are usually described and grouped based upon their location: intramedullary (IM), intradural-extramedullary (IDEM), and extradural (ED). IM lesions are found within the spinal cord parenchyma, comprise only 5% of all spinal lesions, and 50% of these tumors are located in the cervical spine. Ependymomas account for 60% to 70% of all IM tumors found in adults, followed by astrocytomas and hemangioblastomas. Extramedullary-intradural lesions comprise 40% of all spine tumors and may commonly extend to the spinal roots. IDEM tumors include meningiomas and nerve sheath tumors (neurofibromas and schwannomas); each occurs with similar frequency. Only 15% of meningiomas are located in the cervical spine, while nerve sheath tumors have an equal distribution throughout the cervical, thoracic, and lumbar spine. Extradural lesions arise in vertebral bodies or epidural space and comprise 55% of all spine lesions. Primary ED tumors are relatively uncommon, with the vast majority of tumors in this region being metastases. Primary ED tumors include osteoid osteomas, osteblastomas, osteochondromas, hemangiomas, osteosarcomas, chordomas, and chondrosarcomas. Metastatic ED tumors to the spine include breast, lung, prostate, gastrointestinal, and renal cell carcinomas; myeloma; and lymphoma; and they often invade the vertebral column. The cervical spine is the region least often involved by spinal metastases (10%).

In this chapter, we discuss tumors of the three compartments of the spine: IM, IDEM, and ED. We provide the basic presentation, imaging findings, details of surgery, and management of tumors with adjuvant therapies. Additional attention is placed on describing the more common cervical tumors found in adults as well as the most challenging tumors of the cervical spine. Specifically, there are more detailed discussions and case examples of the surgical management of intramedullary ependymomas, cervical schwannomas, and cervical chordomas.

Intramedullary Spinal Tumors

General Information, Clinical Presentation, and Imaging

Patients with intramedullary glial spinal cord tumors may present with pain, sensory dysfunction, and weakness referable to the level of the lesion. A characteristic presentation of an intramedullary tumor is a central, dull aching of a gradual onset that is not referable to a specific neurological location. The symptoms can be of a longer duration for lesions that grow slowly. As the lesion increases in size, the symptoms may progress from the vague ones described above to more neurologically localizing sensory, and even later, motor changes. In contrast, in patients with malignant astrocytomas, symptoms occur rapidly with a mean duration of less than 6 months before diagnosis.

The diagnostic imaging modality of choice, to differentiate the three most common IM lesions (ependymomas, astrocytomas, and hemangioblastomas), to evaluate the possibility of malignancy, and for preoperative evaluation and planning, is gadolinium-enhanced magnetic resonance imaging (MRI). An MRI of the entire spine axis is indicated to evaluate for other lesions or metastasis. IM lesions commonly result in widening of the spinal cord. Also, MRI provides evaluation of associated findings commonly seen with IM lesions, such as edema, hemorrhage, cyst, syringomyelia, and cord atrophy. Intramedullary tumors may be difficult to see on T1-weighted images as they appear isointense to the adjacent spinal cord. T2-weighted images are the most diagnostic, as these tumors often appear hyperintense to the surrounding spinal cord. Although ependymomas often display homogeneous enhancement on MRI, astrocytomas are often much less uniform. This is caused by inconsistent contrast uptake as a result of their irregular margins and associated necrosis. Whereas ependymomas result in symmetric expansion of the spinal cord, astrocytomas are more infiltrative, have margins that are less sharp, and are eccentrically located. Hemangioblastomas can be differentiated from the other tumors by their origin and location on the posterior surface of the spinal cord with the tumor nodule on the pial surface and more intense enhancement than that of ependymomas.

Ependymomas

Ependymomas account for the majority of all intramedullary spinal cord tumors found in adults. They comprise about 60% of all IM spinal cord tumors and are the most common glial tumors of the spinal cord. IM ependymomas arise from the ependymal cells lining the central canal. Ependymomas are benign and slow-growing, centrally located, well-circumscribed and sometimes encapsulated, and they cause symmetric expansion of the cord without infiltration into the surrounding neural tissue. Their arterial supply is most often derived from the anterior spinal artery. Ependymomas appear as reddish or purple-gray masses with many small blood vessels. Associated hemorrhage at the outer margins of the tumor and reactive cysts occur with many IM ependymomas.

Intramedullary ependymomas most commonly occur in the cervical and cervicothoracic regions of the spinal cord. The mean age at presentation is 42 years, and there is a slight female predominance. The most common presenting symptom is neck pain localized to the region of the spine, but patients may also present with dysesthetic pain or numbness and, with larger tumors, with symptoms from neural compression. Given the slow growth and well-circumscribed quality of these tumors, symptoms generally progress slowly, and patients often have a long history prior to diagnosis.

On T1-weighted images, ependymomas appear isointense relative to the neural parenchyma although, infrequently, they may appear hypointense. Heterogeneity and hyperintensity on T1-weighted images may reflect a hemorrhagic component. On T2-weighted images, ependymomas are commonly hyperintense relative to the normal spinal cord. Ependymomas are homogeneously and intensely enhancing with a well-defined border of enhancement. Hemorrhage at the cranial or caudal margin of ependymomas is common and T2-weighted images may demonstrate a low-signal-intensity rim. About half of ependymomas have nonenhancing reactive cysts with similar signal intensity to cerebrospinal fluid. Also, half of cervical ependymomas are associated with a syrinx. Cervical lesions average 4.2 vertebral segments in length.

Astrocytomas

Astrocytomas of the spinal cord are rare in adults and arise from glial cells in the spinal cord. They are less common than ependymomas in the adult population. The majority of IM astrocytomas are low-grade tumors, but approximately 25% of adult spinal cord astrocytomas have anaplastic features. IM astrocytomas are commonly found in the cervical region of the spinal cord.

There is slight male predominance of IM astrocytomas. In adults, the incidence of spinal cord astrocytomas peaks between the third and fifth decades of life, but these tumors may occur in individuals of any age. As with ependymomas, patients often present with symptoms near the level of the tumor. The most common signs and symptoms of spinal cord tumors include localized pain, numbness and paresthesias, unilateral or bilateral weakness, bowel or bladder dysfunction, spasticity, and gait difficulties. Patients with malignant astrocytomas are more likely to present with neurological deficit, given the rapid growth of the tumor and subsequent neural compression.

On imaging, intramedullary astrocytomas of the spinal cord vary in size and length, with 6 vertebral-body segments being the average length. Spinal astrocytomas have variable and heterogeneous enhancement patterns. The tumor margin is often not well defined. Tumor cysts are a common finding, and reactive cysts may be observed at the cranial and caudal ends. IM astrocytomas may be associated with a syrinx. Spinal astrocytomas are more infiltrative, have less defined margins than the other IM lesions, and are more eccentric in location. Spinal astrocytomas are less prone to have extratumoral hemorrhage. MRI may demonstrate significant cord edema, drop metastasis, and leptomeningeal spread with malignant astrocytomas.

Hemangioblastomas

Hemangioblastomas are benign tumors of vascular origin that arise from the erythrocyte precursor. They account for less than 5% of IM tumors. They may occur sporadically or in association with von Hippel-Lindau disease (20% to 30% of cases); these patients typically present with multiple lesions. Patients typically present by age 40 years. Often patients present with pain, weakness, or paresthesias. Hemangioblastomas are localized to the dorsal aspect of the spinal cord. Hemangioblastomas are characterized by prominent vascularity, large reactive cysts, the coexistence of a syrinx, and a widened, edematous cord. MRI signal intensity of hemangioblastomas is similar to those of ependymomas, but the tumor nodule, on the pial surface, commonly has more intense enhancement. Flow voids may be present and there may be local edema of the cord around hemangioblastomas.

Operative Techniques (See Figures 32-1 and 32-2)

Intramedullary Tumors

The patient is positioned prone on gel rolls in a Mayfield head holder with the arms tucked to the side, with care taken to pad all pressure points. We use intraoperative neurophysiologic monitoring with somatosensory evoked potentials, transcranial motor evoked potentials, and continuous electromyography for all IM cervical spine tumors. The use of total intravenous anesthesia allows for effective monitoring during tumor resection. We maintain the mean arterial pressure at a normal range to ensure adequate spinal cord perfusion. A lateral x-ray with skin markers in place allows for identification of the relevant level of the spine and a precise skin exposure. A standard dorsal midline approach is used. A subperiosteal dissection of the paraspinal musculature exposes the lamina and spinous processes. Prior to laminectomy, the level is confirmed again with radiograph. Generally, we perform a joint-sparing laminectomy at the vertebral level above and below the area of the lesion. If there is a suspicion of a high-grade astrocytoma and we obtain biopsy confirmation of this lesion, we target the location of the greatest size of the mass, and may not require a laminectomy overlying the entire lesion. Prior to dural opening, the tumor is precisely visualized with ultrasound to confirm adequate exposure. A durotomy is made in the midline, and the dural edges are sutured to the soft tissues laterally, exposing the arachnoid overlying the spinal cord. Using an operating microscope, the arachnoid is opened and tacked laterally to the dural edges with vascular clips. Care is taken to avoid any blood rundown into the operative field by placing sponges along the outer dural margin. For ependymomas, or lesions not extending to the dorsal surface, we prefer approaching the tumor, if possible, with a midline myelotomy between the dorsal columns. For more lateral lesions, a myelotomy dorsal to the dorsal root entry zone approach is performed. We use neurophysiological monitoring to define the dorsal columns and midline sulcus, as the midline may be difficult to identify due to the tumor growth. A bipolar cautery is used on the pial surface, and it is sharply incised. The myelotomy is extended beyond both poles of the tumor to facilitate a gross total resection. We make the best attempt to preserve all veins and arteries. The dorsal columns are dissected apart. Commonly, we enhance exposure with retraction of the cord with a pial suture.

image

FIGURE 32-1 A, Intraoperative illustration of a patient with a C4–C7 ependymoma. The durotomy is completed, and the arachnoid is incised (dashed line)B, Tumor dissection is initiated in the middle portion of the tumor, which is the bulkiest. C, Great caution must be exerted while coagulating branches of the anterior spinal artery supplying the neoplasm along the anterior aspect of the cord to avoid occluding the anterior spinal artery. (a = artery)

(From Neurosurgery 51:1162-1174, 2002.)

image

FIGURE 32-2 Spinal cord ependymoma. A, Preoperative T1-intensity, gadolinium-enhanced MRI scan of a patient with a thoracic cord intramedullary ependymoma. B, Postoperative T1-intensity, gadolinium-enhanced MRI scan of the same patient showing complete resection of the neoplasm. C, Intraoperative photograph of the same patient showing the spinal cord before the myelotomy. D, Ependymoma mushrooming out of the myelotomy. E, Tumor elevated caudally, with a forceps used to dissect the anterior plane. F, En bloc resected ependymoma.

(From Neurosurgery 51:1162-1174, 2002.)

Demarcating and establishing a plane between the parenchyma and tumor is key to achieving a gross total or more aggressive resection. Regardless of the suspected tumor pathology, we always send tumor specimens early in the dissection for evaluation with frozen pathology. The bulkiest component of the lesion is often in the center, and thus a good place to begin the dissection, as there is decreased potential for harm to surrounding neural structures. As mentioned earlier, it is also important to have complete exposure to the poles of the tumor. For ependymomas, we generally can identify and develop a clear plane between cord and tumor, and the tumor capsule is dissected circumferentially from the spinal cord parenchyma. We recommend en bloc resection of the tumor whenever possible, as it reduces the potential for tumor spillage, avoids encountering excessive bleeding from the tumor during dissection, and thus allows maintenance of better surgical planes. Dissection along the anterior median raphe is usually the most difficult portion of the surgery, as the tumor tends to adhere to this thin segment of the cord. Because small branches of the anterior spinal artery penetrate the neoplasm along the anterior aspect of the cord, great care must be taken to avoid disrupting the anterior spinal artery. The final step in removing the ependymoma after dissection from the ventral surface is the separation from the anterior spinal artery.

For large tumors or ones with indistinct planes, it may be necessary to debulk the mass with an ultrasonic aspirator. When en bloc resection is not feasible due to an inability to clearly visualize the dissection planes, internal debulking may be performed to decrease the amount of traction on the cord. The major disadvantage of extensive debulking is fragmentation of the tumor, thereby destroying the correct dissection planes. For large tumors, after debulking, it may be possible to remove further tumor capsule and delineate the tumor margins from the cord.

Generally, for an ependymoma or low-grade astrocytoma, we will always attempt a total resection if there are no persistent changes on neurophysiological monitoring. If there are neurological changes on monitoring, we typically elect to perform a second staged resection at a later date. For biopsy-confirmed anaplastic astrocytomas we resect as much abnormal appearing tissue as possible and only attempt a total resection if there is no evidence of significant changes on monitoring, and the tumor is easily resectable with a visible cord-to-tumor interface and is not disseminated. The extent of resection may be confirmed via intraoperative ultrasonography. We do not perform more than a biopsy on a glioblastoma multiforme or a disseminated anaplastic astrocytoma. Gross total resection is the acceptable surgical option for a hemangioblastoma.

After tumor resection, we achieve hemostasis, avoiding the temptation to coagulate any of the surface vessels. The tacked sutures on the pia and dura are removed. The dura is closed primarily, in a watertight fashion. The subarachnoid space is irrigated to remove any blood prior to final closure, and a Valsalva maneuver confirms lack of CSF egress. Fibrin glue is placed over the dural closure. The wound is closed in the standard fashion and we leave a subfascial drain until there is limited output. We allow the patient to ambulate and sit up immediately after surgery.

In the authors’ experience with intramedullary cervical tumor resection, patients presenting with myelopathic motor symptoms or those undergoing three or more levels of cervical laminectomy were found to have an increased likelihood of developing subsequent symptomatic instability requiring fusion, and we elect to fuse these patients with standard lateral mass and pedicle screws at the time of tumor resection. In the absence of myelopathy and/or the need for three-or-more-level laminectomies, we prefer laminoplasty or laminectomy if the majority of the facet is maintained.

Postsurgical Management

The best current treatment of ependymomas consists of gross total resection without need for adjuvant therapy. The implementation of radiotherapy for ependymomas is warranted in cases of malignancy or disseminated tumor. In the case of a subtotal resection, we generally consider a secondary stage resection. The senior author (ZG) resected 26 spinal cord ependymomas, 11 of which had previous treatment with surgery and/or radiation therapy. A gross total resection was achieved in 88% of patients. Only one patient developed a recurrence over a mean follow-up period of 31 months. This study demonstrated that radical surgical resection of spinal cord ependymomas can be safely achieved in the majority of patients. A trend toward neurological improvement from a postoperative deficit can be expected between 1 and 3 months after surgery and continues for up to 1 year. The best predictor of outcome is the preoperative neurological status.

In the setting of residual ependymoma or low-grade astrocytoma that is not surgically resectable, radiotherapy is advocated. The dose is generally lower for these IM lesions compared to the adjuvant treatment of anaplastic astrocytomas (AAs) or glioblastoma multiforme. Higher grade lesions receive higher doses, and disseminated disease requires complete craniospinal radiation. There are no well-defined chemotherapeutic or radiosurgery regimens for IM tumors, but they remain possible treatment options for the future. In general, most authors only recommend biopsy for high-grade astrocytomas, followed by radiotherapy, but others have advocated for more aggressive surgical treatment of nondisseminated anaplastic astrocytomas. For example, in one large series of 35 high-grade spinal astrocytomas, radical resection of AAs was associated with a trend of increased overall survival in nondisseminated AA cases. The overall survival rate with these high-grade lesions remains poor.

Intradural-Extramedullary Spinal Cord Tumors

General Information, Clinical Presentation, and Imaging

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