You are in: eMedicine Specialties > Radiology > BRAIN/SPINE Astrocytoma, SpineArticle Last Updated: Oct 1, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Michael E Tobias, MD, Fellow in Pediatric Neurosurgery, Lebonheur Children's Hospital, University of Tennessee Coauthor(s): V Michelle Silvera, MD, Division of Pediatric Neuroradiology, Clinical Instructor, Boston Children's Hospital; George Jallo, MD, Associate Professor of Neurosurgery, Pediatrics and Oncology, Department of Neurosurgery, Division of Pediatric Neurosurgery, Johns Hopkins University School of Medicine Editors: Mahesh R Patel, MD, Chief of MRI, Department of Radiology, Santa Clara Valley Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; C Douglas Phillips, MD, Professor, Departments of Radiology, Neurosurgery, and Otolaryngology, University of Virginia Health Sciences Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; L Gill Naul, MD, Professor and Head, Department of Radiology, Texas A&M University College of Medicine; Chair, Department of Radiology, Chief, Section of Magnetic Resonance Imaging, Scott and White Memorial Hospital and Clinic Author and Editor Disclosure Synonyms and related keywords: spinal cord tumor, intramedullary spinal cord tumor, diffuse fibrillary astrocytoma INTRODUCTIONSection 2 of 10
  BackgroundAstrocytomas of the spinal cord are rare tumors that arise from astrocytes in the spinal cord and occur in the adult and pediatric populations. Most spinal cord astrocytomas are benign, low-grade tumors that are readily diagnosed with magnetic resonance imaging (MRI). These tumors characteristically cause the spinal cord to appear expanded, often with cysts and a variable enhancement pattern. In the past, few treatment options were available for these astrocytomas. However with the advent of modern surgical techniques, intraoperative microscopy, intraoperative ultrasonography, ultrasonic aspiration, and electrophysiologic monitoring, most intramedullary spinal cord tumors can be surgically removed, with acceptable morbidity and mortality rates. PathophysiologyThe 4 types of macroglial cells found in the central nervous system (CNS) are astrocytes, Schwann cells, oligodendrocytes, and ependymal cells; these cells serve a variety of supportive functions. Astrocytomas arise from astrocytes, which provide structural and metabolic support to the CNS. On microscopy, spinal cord astrocytomas are similar in appearance to cerebral astrocytomas. In general, astrocytomas are divided into 2 groups: diffuse fibrillary astrocytomas and specialized (or circumscribed) astrocytomas. The specialized astrocytomas distinguish themselves from the diffuse, low-grade astrocytomas in that they show astrocytic differentiation and do not widely infiltrate the adjacent CNS parenchyma. As such, the specialized astrocytomas are easier to surgically remove than diffuse fibrillary astrocytomas. Consequently, more complete surgical resections—and therefore better long-term prognoses—are obtained with specialized astrocytomas than with diffuse, low-grade lesions. The cause of astrocytomas—or, for that matter, all glial tumors—is unknown. However, the literature does describe chromosomal abnormalities and overexpression of oncogenes as possible causes of spinal cord astrocytomas. Nonetheless, to the authors' knowledge, the available data or research findings do not explain the exact cause of these tumors. FrequencyUnited StatesSpinal cord tumors are rare, with an incidence of 1.1 cases per 100,000 people, and represent 4-10% of all CNS tumors. Approximately 30% of pediatric and adult intramedullary spinal cord tumors are astrocytomas. Together, astrocytomas and ependymomas account for approximately two thirds of all intramedullary spinal cord tumors, with astrocytomas the most common in the pediatric population and ependymomas the most common in adults. The most common tumors that involve the spine are metastatic disease to bone. Lung, breast, prostate, and other cancers can spread hematogenously to the vertebral bodies or to the epidural soft tissues. Metastatic disease accounts for about 55% of all tumors that involve the spine. Mortality/MorbidityMortality Most spinal cord gliomas are benign, low-grade neoplasms, and it has been well documented that radical surgery can decrease the neurologic symptoms and increase survival time.1, 2, 3 If a patient with a low-grade astrocytoma of the spinal cord undergoes a gross total resection, the likelihood of progression-free survival at 5 years is greater than 50%.1 PrognosisHigh-grade astrocytomas of the spinal cord are associated with a poor prognosis. On occasion, a low-grade astrocytoma of the spinal cord can progress to a malignant astrocytoma. This transformation and progression can take months to years. MorbidityMany potential complications are associated with surgical resection of a spinal cord astrocytoma. The risk of a postoperative motor deficit in a patient without preoperative weakness is approximately 5%. If a patient has motor weakness before surgery, the risk of a motor deficit is increased postoperatively.2 Injury to the posterior columns of the spinal cord can cause loss of proprioception. This is an obvious surgical risk, given the posterior surgical approach that is taken to remove spinal cord tumors. Injury to the posterior columns is more common in adults than in children. (See also Intervention.) SexReports suggest a slight male predominance with spinal cord astrocytomas. The male-to-female ratio ranges from 1:1 to 1.5:1. AgeThe incidence of spinal cord astrocytomas peaks between the third and fifth decades of life, but these tumors may occur in individuals of any age.
AnatomySpinal cord tumors are intradural intramedullary lesions that arise from the glial cells in the spinal cord. Spinal cord astrocytomas can occur at any level, with the thoracic cord being the most common site and the cervical cord being the second most common location. Holocord tumors are sometimes seen in children but are rarely present in adults. Spinal cord astrocytomas occasionally have an exophytic component that projects into the subarachnoid space. About 40% of astrocytomas are associated with tumoral cysts. An associated spinal cord syrinx is often a secondary finding. Clinical DetailsPatients usually present with symptoms at or below the level of the spinal cord tumor. The most common signs and symptoms of spinal cord tumors include back pain, numbness and paresthesias, unilateral or bilateral weakness, ataxia, bowel or bladder dysfunction, mild spasticity, and gait difficulties. Back pain may be localized or radicular and typically increases at night—likely because of increased venous congestion in the spinal compartment in the recumbent position, which increases distention of the dural tube. A full neurologic examination is necessary for any patient with a possible spinal cord tumor. The spinal axis should be palpated for any areas of tenderness, as approximately 70% of patients have spinal pain. All motor groups should be examined to evaluate for any focal weakness. Patients may have a sensory level or a deficit of a particular sensory modality. Intramedullary spinal cord astrocytomas may cause increased reflexes, clonus, mild spasticity, and a positive Babinski sign (ie, plantar reflex, in which the great toe extends in response to a stimulus). The examination must also include watching the patient walk and carefully evaluating his or her gait. A rectal examination should be performed to assess for sphincter control. Preferred ExaminationThe examination modality of choice for diagnosing and evaluating spinal cord astrocytomas is a contrast-enhanced MRI of the spine with a closed magnet. The extent of the tumor mass, the enhancement pattern of the tumor, and the presence of associated tumoral cysts and syringeal cavities are well delineated on MRI. DIFFERENTIALSSection 3 of 10
Astrocytoma Ependymoma, Spine Hemangioblastoma, Spine Meningioma, Spine Spinal Cord Tumors: Management of Intradural Intramedullary Neoplasms Other Problems to Be ConsideredIntramedullary germ cell tumors RADIOGRAPHSection 4 of 10
FindingsPlain radiography is of limited diagnostic value in evaluating patients with a potential spinal cord tumor. On occasion, widening of the spinal canal, widening of the interpedicular distance, and scalloping of the dorsal aspects of the vertebral bodies can be appreciated on plain radiographs as a late imaging finding. Both typical and atypical scoliotic curvatures can be seen in patients with a spinal cord tumor. Plain radiographs, however, are helpful in assessing bony changes of the spine that can occur after the spinal cord tumors are treated. Examples of such changes are progressive scoliosis, kyphotic deformities, and spinal instability. CT SCANSection 5 of 10
FindingsComputed tomography (CT) scanning is of limited value in the assessment of spinal cord tumors. CT scans may depict bony changes of the spine, which may occur as late secondary findings in patients with spinal cord tumors; such changes include pedicular erosion, widening of the spinal canal, and dorsal scalloping of the vertebral bodies. Degree of ConfidenceCT scanning is not useful in examining the spinal cord itself. CT myelography is indicated in the workup of spinal cord tumors only if MRI is contraindicated (eg, because of the presence of a pacemaker or implant). With regard to the spinal cord, CT myelography can demonstrate only the presence or absence of spinal cord expansion. The cause of the spinal cord expansion is usually not discernible during CT myelography because such expansions secondary to a tumor, a cyst, a syrinx, and edema have similar appearances. MRI has replaced CT myelography as the study of choice in diagnosing spinal cord tumors because of its superior imaging resolution of the spinal cord itself. MRISection 6 of 10
FindingsMRI enables detailed assessment of spinal cord tumors with high-resolution imaging of the soft tissues. When spinal tumors are evaluated on MRI, they are classified into 3 groups: extradural, intradural and extramedullary, or intramedullary. Extradural masses are located in the epidural space and arise from the vertebral bodies or epidural soft tissues. Intradural extramedullary tumors arise from the leptomeninges, nerve roots, or dura, or they represent subarachnoid spread from a distant tumor. Intramedullary tumors originate in the spinal cord; thus, spinal cord astrocytomas are intramedullary tumors. The spinal cord is typically enlarged at the level of tumor. This feature helps in differentiating spinal cord tumors from non-neoplastic diseases that may mimic a spinal cord neoplasm, such as inflammatory or demyelinating processes. T1- and T2-weighted images demonstrate the extent of tumor, the solid and cystic components of the tumor, spinal cord edema, reactive cysts, and syringeal cavities. Spinal cord tumors are typically isointense or hypointense on T1-weighted images and hyperintense on T2-weighted images. T1-weighted gadolinium-enhanced MRIs add information for characterizing the enhancement pattern of the tumor by distinguishing between enhancing and nonenhancing components of tumor and by distinguishing between tumoral and reactive cysts. Astrocytomas of the spinal cord vary in size and length, with 7 vertebral-body segments being the average length.4 Tumoral enhancement is variable, and some astrocytomas are completely nonenhancing. The tumor margins may be well defined or indistinct. Tumoral cysts are a common finding, and reactive cysts may be observed at the tumoral poles. Drop metastases (ie, intradural extramedullary spinal metastases that arise from intracranial lesions) in the subarachnoid space are most commonly seen with high-grade astrocytomas but can occasionally occur with low-grade astrocytomas. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape. ULTRASOUNDSection 7 of 10
FindingsUltrasonography is useful during surgery to determine the extent of resection. Before the dura is incised, intraoperative ultrasonography is used to define the superior and inferior margins of the mass and to locate any cysts in or adjacent to the lesion. Any cysts that are encountered should be drained. INTERVENTIONSection 8 of 10
Surgery All patients with astrocytoma of the spine are operated on with the goal of a gross total resection or a near-total resection of tumor, and all procedures should be performed in conjunction with electrophysiologic monitoring, with the electrophysiologist present for the entire procedure. The patient is placed in the prone position and electrodes are arranged to monitor sensory-evoked potentials (SEPs) and motor-evoked potentials (MEPs). Monitoring is updated every few seconds to provide the surgeon with important information regarding the safety of resection during an attempted gross total resection. The location for laminectomy is based on findings on preoperative MRI. Intraoperative ultrasonography is used to define the margins of the tumor and to locate any cysts. The spinal cord is often widened at the location of the mass, and the lesion often distorts the normal anatomy. The Cavitron ultrasonic surgical aspirator (CUSA; Integra Radionics, Inc, Burlington, Mass) is used to fragment and suction the tumor tissue without damaging the nearby normal spinal cord. The carbon dioxide microsurgical laser is also precise enough to be used safely at the tumor–spinal cord interface. However, use of the laser is tedious and generally not recommended for resections of large spinal astrocytomas. Close attention is required when closing the fascia at the end of surgery to avoid a cerebrospinal fluid (CSF) leak. If a CSF leak is present, the patient must be aggressively treated with suture closure, lumbar drainage, and wound revision, as indicated. Scoliosis and/or kyphosis may evolve or progress following the resection of a spinal cord astrocytoma. If a patient develops new signs of myelopathy, possible causes include recurrent tumor, further extension of a syringeal cavity, leptomeningeal spread of tumor, and progression of spinal deformity. After surgery, patients must be closely monitored with clinical and imaging evaluations. If scoliosis or kyphosis of the spine progresses, an orthopedic surgeon who specializes in spinal deformity should follow up the patient. If a patient presents with hydrocephalus after a spinal cord tumor is surgically removed, leptomeningeal spread of tumor should be considered.5, 6, 7 Radiation therapy Radiation therapy is generally not advocated for low-grade spinal cord astrocytomas. The treatment of choice for these tumors is surgery with a gross total resection as the goal. If a tumor recurs in the spinal cord, repeat surgery rather than radiation therapy or chemotherapy is the preferred treatment option. Radiation treatment should be considered only if resection of the tumor was incomplete. Radiation treatment in combination with surgery is recommended in patients with high-grade astrocytomas of the spinal cord. Radiation treatment after surgery increases rates of spinal kyphosis and subluxation. Long-term complications of radiation therapy include secondary tumors, most commonly meningiomas, with an incidence as high as 20% over 30-year follow-up. In children younger than 5 years, radiation treatment is generally avoided to prevent injury to the still-developing CNS. Chemotherapy Chemotherapy as an adjunct to surgery is generally not recommended for low-grade astrocytomas. For high-grade astrocytomas, several chemotherapeutic protocols are available as part of adjuvant treatment plans to surgery. Although the outcome for high-grade astrocytomas remains poor, evidence suggests that survival times can be improved with aggressive surgical excision and adjuvant therapy. Future interventions Over the years, the prognosis has greatly improved for patients with surgically resected low-grade astrocytomas but not for those with high-grade astrocytomas. Patients with malignant spinal cord astrocytomas continue to have a dismal prognosis. Research data have suggested that aggressive treatment can improve both survival time and the overall outcome of patients with high-grade spinal cord astrocytomas. A combination of surgery and adjuvant radiation and chemotherapy may prolong survival time and improve outcome. Allen et al studied 18 pediatric patients who were newly diagnosed with high-grade spinal cord astrocytomas.9 The children underwent radical surgical excision that was followed by 2 cycles of 8-in-1 chemotherapy (ie, 8 drugs in 1 day) before radiation therapy and then 8 additional cycles of chemotherapy. Thirteen of the 18 children were confirmed to have high-grade spinal cord astrocytomas by a centralized neuropathology review: 8 children had anaplastic astrocytoma, 4 had glioblastoma multiforme, and 1 had mixed malignant glioma. The 5-year survival rate for the 13 patients was 54%. Medical/Legal Pitfalls
MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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