(Radiographics. 2000;20:1721-1749.)
© RSNA, 2000
Neoplasms of the Spinal Cord and Filum Terminale: Radiologic-Pathologic Correlation1
Kelly K. Koeller, CDR, MC, USN,
R. Scott Rosenblum, DO and
Alan L. Morrison, CDR, MC, USN
1 From the Departments of Radiologic Pathology (K.K.K., R.S.R.) and Neuropathology (A.L.M.), Armed Forces Institute of Pathology, 14th St at Alaska Ave, Bldg 54, Rm M-121, Washington, DC 20306-6000; and the Departments of Radiology and Nuclear Medicine (K.K.K.) and Pathology (A.L.M.), Uniformed Services University of the Health Sciences, Bethesda, Md. Received May 11, 2000; revision requested May 30; revision received July 12; accepted July 18. Address correspondence to K.K.K. (e-mail: koeller@afip.osd.mil).
 |
Abstract
|
|---|
Intramedullary spinal cord neoplasms are rare, accounting for about 4%10% of all central nervous system tumors. Despite their rarity, these lesions are important to the radiologist because magnetic resonance (MR) imaging is the preoperative study of choice to narrow the differential diagnosis and guide surgical resection. On contrast materialenhanced MR images, intramedullary spinal tumors almost always manifest as expansion of the spinal cord and show enhancement. Syringohydromyelia and cystic lesions are frequently associated with intramedullary tumors. Nontumoral cysts tend to be located at the poles of the tumors and do not enhance on contrast-enhanced MR images, whereas cysts within the substance of the tumor are considered tumoral cysts and typically demonstrate peripheral enhancement. Spinal cord ependymomas are the most common type in adults, and cord astrocytomas are most common in children. Both entities constitute up to 70% of all intramedullary neoplasms. A central location within the spinal cord, presence of a cleavage plane, and intense homogeneous enhancement are imaging features that favor an ependymoma. Intramedullary astrocytomas are usually eccentrically located within the cord, are ill defined, and have patchy enhancement after intravenous contrast material administration. Even with these characteristics, it may not be possible to differentiate these two entities on the basis of imaging features alone. Cord hemangioblastomas are the third most common type of intramedullary spinal tumor. Gangliogliomas commonly extend over more than eight vertebral segments. Paragangliomas and primitive neuroectodermal tumors have an affinity for the filum terminale and cauda equina. Other spinal cord tumors include metastatic disease, which is characterized by prominent cord edema for the size of the enhancing portion, and primary lymphoma.
Index Terms: Spinal cord, MR, 30.1214 • Spinal cord, neoplasms, 30.32, 30.33, 30.363 • Spinal cord, US, 30.1298
|
LEARNING OBJECTIVES FOR TEST 6
|
|---|
After reading this article and taking the test, the reader will be able to:- List the essential imaging features of intramedullary spinal cord neoplasms.
- Identify the characteristic imaging appearances of the different types of intramedullary spinal cord neoplasms that allow a specific diagnosis to be favored.
- Describe the correlation of the imaging appearance with the gross pathologic appearance in intramedullary spinal neoplasms.
|
Introduction
|
|---|
Spinal intramedullary neoplasms account for about 4%–10% of all central nervous system (CNS) tumors and about 2%–4% of CNS glial tumors. Although spinal cord neoplasms constitute only 20% of all intraspinal tumors in the adult population, they constitute 35% of such tumors in children (1). Most spinal cord neoplasms are malignant, and 90%–95% are classified as gliomas. Most of these glial neoplasms are either ependymomas or astrocytomas. Ependymomas are the most common glial tumor in adults, whereas astrocytomas are the most common intramedullary tumor in children. Nonglial neoplasms, including hemangioblastomas, paragangliomas, metastases, lymphoma, and primitive neuroectodermal tumors (PNETs), are much less common (Table 1). In contrast to intracranial neoplasms, the vast majority of spinal cord neoplasms, including even low-grade forms, enhance after the administration of contrast material to at least some degree. Enhanced areas probably represent more active portions of the tumors and may indicate potential sites for biopsy if resection is not feasible.
In this article, we correlate the imaging features of intramedullary spinal neoplasms with the underlying pathologic findings by using cases from the Thompson Archives of the Department of Radiologic Pathology at the Armed Forces Institute of Pathology, Washington, DC. After reviewing the use of magnetic resonance (MR) imaging in the evaluation of spinal cord neoplasms, we describe and illustrate the prevalence and clinical, pathologic, and imaging characteristics of ependymoma and its variants, astrocytoma, ganglioglioma, hemangioblastoma, paraganglioma, metastasis, lymphoma, and PNETs.
|
Overview of Intramedullary Spinal Neoplasms
|
|---|
Traditional imaging modalities (conventional radiography and computed tomography [CT]) of the mid-20th century often failed to reveal the true extent of intramedullary spinal neoplasms until gross expansion of the spinal canal had occurred. Myelography, either with conventional radiography or CT, revealed an intramedullary mass as a complete or partial block in the flow of intrathecal contrast material (Fig 1). Myelography, however, could rarely help define the character of the spinal cord lesion. The development of magnetic resonance (MR) imaging revolutionized the noninvasive investigation of these lesions. Identification of internal structural abnormalities of the spinal cord, such as cysts, syringohydromyelia, hemorrhage, and edema, became routine in the setting of an intramedullary spinal mass. Not surprisingly, MR imaging is the current imaging modality of choice in the evaluation of spinal cord masses.
View larger version (112K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 1. Intramedullary astrocytoma in an 18-year-old woman with progressive paresis, paresthesia of the lower extremities, and difficulty voiding. CT myelogram shows a near-compete block of intrathecal contrast material (arrowheads) secondary to an intramedullary mass. No additional information can be discerned from the spinal cord lesion, which reflects a substantial shortcoming of this imaging modality.
|
|
The "basic" spinal MR imaging study should include unenhanced T1- and T2-weighted images in the sagittal plane and contrast materialenhanced T1-weighted images in the sagittal and axial planes. Contrast-enhanced images are especially valuable for determining the solid portion of an intramedullary neoplasm and identifying associated cysts and other features that often modify the differential diagnosis (2). Advances in the development of imaging software and improved surface coil technology have facilitated the imaging of a patient suspected of having intramedullary disease. Phased-array surface coils, in particular, save valuable time because they allow basion-to-conus evaluation of the spinal cord in a single sequence (3). In addition, postoperative assessment is best performed with a contrast-enhanced MR imaging examination, which has become the sine qua non for establishing the presence of recurrent tumor (4—7). Still, although MR imaging is a powerful tool, it is not perfect. In a series of 171 patients with spinal cord tumors (8), MR imaging findings could correctly suggest the histologic diagnosis in only 70% of cases. In particular, the differentiation of ependymoma from astrocytoma was the most difficult with MR imaging alone.
There are three important tenets in the use of MR imaging to evaluate patients suspected of having an intramedullary spinal process. First, the essential imaging criterion for an intramedullary spinal neoplasm is cord expansion (9). If this feature is absent, it should suggest a nonneoplastic etiology, such as demyelinating disease, sarcoidosis, amyloid angiopathy, pseudotumor, dural arteriovenous fistula, cord infarction, chronic arachnoiditis, or cystic myelomalacia (10–12). Obviously, the differentiation of neoplastic from nonneoplastic entities is crucial to the surgeon. If a lesion is likely to be a neoplasm, the patient may be a candidate for a gross total resection of the mass after the tumor is debulked. If the lesion is not likely to be a tumor, only a biopsy is initially indicated. Once the nonneoplastic cause is confirmed, appropriate (and usually nonsurgical) therapy can be instituted. Accordingly, patients with nonsurgical disease can be spared the risks of an aggressive surgical approach with much less postoperative morbidity (10). In a series of 212 patients suspected of having intramedullary disease (10), nine (4%) had nonneoplastic lesions. None of the nine patients had imaging evidence of cord expansion.
Second, the vast majority of intramedullary spinal neoplasms show at least some enhancement following the intravenous administration of gadolinium-based contrast material (6,12–15). Accordingly, in the evaluation of a patient suspected of harboring such a lesion, obtaining contrast-enhanced images in at least two different planes is essential, not only for limiting the differential diagnosis but also for planning surgery. However, although almost all spinal cord tumors show some enhancement, the converse is not true: The absence of enhancement does not exclude an intramedullary neoplasm in the presence of cord expansion (16).
Third, cysts are a common associated finding in the setting of an intramedullary spinal tumor. There are two basic types of cysts: tumoral and nontumoral. Cysts located at the poles of the solid portion of the tumor usually represent simply reactive dilatation of the central canal (syringomyelia). Approximately 60% of all intramedullary spinal tumors demonstrate these rostral or caudal (also called polar or satellite) cysts (Fig 2). In these cases, only the solid component of a spinal cord tumor must be resected; the rostral and caudal cysts will either decompress upon removal of the solid portion or they can be aspirated by the surgeon at resection (17). These cysts are not part of the tumor itself and should not enhance on imaging studies. They are not septated and do not show echogenicity within their walls at intraoperative ultrasonography (US) (17). Polar cysts are believed to arise from the egress of fluid produced by these neoplasms through the central canal and may also explain the relative lack of symptoms seen in cases of intramedullary spinal neoplasms (18). In contrast, tumoral cysts are contained within the tumor itself and frequently show peripheral enhancement (Fig 3) (16). They tend to be more commonly seen in astrocytomas than in ependymomas (17). Identification of the location of the solid enhancing portion of the tumor (including enhancing tumoral cysts) is vital because current neurosurgical techniques allow laminotomy or laminectomy to be limited only to this zone, thereby decreasing potential surgical morbidity. Finally, intraoperative monitoring of somatosensory-evoked potentials and use of the Cavitron ultrasonic surgical aspirator (Cusa Valleylab, Boulder, Colo) have greatly facilitated the surgical resection of many intramedullary neoplasms (8,19).
View larger version (122K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2a. Ependymoma and meningiomas in a 27-year-old woman with neck pain. (a) Sagittal T1-weighted MR image shows lower cervical cord expansion. Except for a cystlike area of low signal intensity (arrow), the mass is nearly isointense relative to the normal spinal cord. There are separate intradural, extramedullary masses (arrowheads) of the intradural compartment at C1 and C3-4. (b) Contrast-enhanced sagittal T1-weighted MR image demonstrates homogeneous enhancement of the oval mass (arrows) extending from C5-6 to T1. The extramedullary lesions (arrowheads) also enhance intensely. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement within the cervical spinal cord. Results of histologic examination confirmed that the intramedullary mass was an ependymoma and the extramedullary lesions were meningiomas. v = vertebral body.
|
|
View larger version (127K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2b. Ependymoma and meningiomas in a 27-year-old woman with neck pain. (a) Sagittal T1-weighted MR image shows lower cervical cord expansion. Except for a cystlike area of low signal intensity (arrow), the mass is nearly isointense relative to the normal spinal cord. There are separate intradural, extramedullary masses (arrowheads) of the intradural compartment at C1 and C3-4. (b) Contrast-enhanced sagittal T1-weighted MR image demonstrates homogeneous enhancement of the oval mass (arrows) extending from C5-6 to T1. The extramedullary lesions (arrowheads) also enhance intensely. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement within the cervical spinal cord. Results of histologic examination confirmed that the intramedullary mass was an ependymoma and the extramedullary lesions were meningiomas. v = vertebral body.
|
|
View larger version (108K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 2c. Ependymoma and meningiomas in a 27-year-old woman with neck pain. (a) Sagittal T1-weighted MR image shows lower cervical cord expansion. Except for a cystlike area of low signal intensity (arrow), the mass is nearly isointense relative to the normal spinal cord. There are separate intradural, extramedullary masses (arrowheads) of the intradural compartment at C1 and C3-4. (b) Contrast-enhanced sagittal T1-weighted MR image demonstrates homogeneous enhancement of the oval mass (arrows) extending from C5-6 to T1. The extramedullary lesions (arrowheads) also enhance intensely. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement within the cervical spinal cord. Results of histologic examination confirmed that the intramedullary mass was an ependymoma and the extramedullary lesions were meningiomas. v = vertebral body.
|
|
View larger version (120K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3a. Ependymoma in a 32-year-old woman with upper- and lower-extremity weakness and numbness and bowel and bladder dysfunction. (a) Contrast-enhanced sagittal T1-weighted MR image demonstrates a heterogeneously enhancing mass expanding the cervical spinal cord. A cyst with faint peripheral enhancement (arrowhead) is seen at the superior pole of the mass. (b) Sagittal T2-weighted MR image reveals that the mass is predominantly isointense relative to the spinal cord, with scattered areas of high signal intensity. There is a curvilinear area of low signal intensity (arrowheads) at the C2-3 level, which is suggestive of hemorrhage. (c) Intraoperative photograph demonstrates the lobulated, irregular mass with areas of hemorrhage (arrows).
|
|
View larger version (137K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3b. Ependymoma in a 32-year-old woman with upper- and lower-extremity weakness and numbness and bowel and bladder dysfunction. (a) Contrast-enhanced sagittal T1-weighted MR image demonstrates a heterogeneously enhancing mass expanding the cervical spinal cord. A cyst with faint peripheral enhancement (arrowhead) is seen at the superior pole of the mass. (b) Sagittal T2-weighted MR image reveals that the mass is predominantly isointense relative to the spinal cord, with scattered areas of high signal intensity. There is a curvilinear area of low signal intensity (arrowheads) at the C2-3 level, which is suggestive of hemorrhage. (c) Intraoperative photograph demonstrates the lobulated, irregular mass with areas of hemorrhage (arrows).
|
|
View larger version (112K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 3c. Ependymoma in a 32-year-old woman with upper- and lower-extremity weakness and numbness and bowel and bladder dysfunction. (a) Contrast-enhanced sagittal T1-weighted MR image demonstrates a heterogeneously enhancing mass expanding the cervical spinal cord. A cyst with faint peripheral enhancement (arrowhead) is seen at the superior pole of the mass. (b) Sagittal T2-weighted MR image reveals that the mass is predominantly isointense relative to the spinal cord, with scattered areas of high signal intensity. There is a curvilinear area of low signal intensity (arrowheads) at the C2-3 level, which is suggestive of hemorrhage. (c) Intraoperative photograph demonstrates the lobulated, irregular mass with areas of hemorrhage (arrows).
|
|
Some clinical associations with intramedullary spinal cord tumors are noteworthy. Intramedullary spinal neoplasms are more common in patients with neurofibromatosis, with ependymomas occurring more often in patients with type 2 disease and with astrocytomas occurring more frequently in those with type 1 disease. It is speculated that the same molecular mechanisms responsible for the increased prevalence of intracranial tumors in patients with neurofibromatosis also cause the increased rate for intraspinal tumors (20). The biologic behaviors of neoplasms of the cervicomedullary junction are more like those of spinal cord tumors (more benign) than those of brainstem gliomas (more aggressive) (21,22). Finally, the higher the location of an intramedullary spinal tumor, the more likely that a syrinx will develop (23).
|
Glial Neoplasms
|
|---|
Ependymoma
Prevalence.—Ependymoma is the most common intramedullary spinal neoplasm in adults, accounting for up to 60% of all glial spinal cord tumors (19). From the four largest studies of patients with spinal cord ependymomas reported in the literature (5,19,24,25), the following demographic information emerges: These lesions tend to manifest in young adulthood, with a mean age at presentation of 38.8 years and are more common in male patients (57.4%). Cord ependymomas occur most commonly in the cervical region, with 44% involving the cervical cord alone and an additional 23% extending into the upper thoracic region. About 26% are located in the thoracic cord alone. Only 6.5% involve either the distal thoracic cord or the conus medullaris (5,19,24,25). Myxopapillary ependymoma, a variant type, is, in rare cases, found in the subcutaneous tissue of the sacrococcygeal region, usually without any connection with the spinal canal (26). It is believed that these arise from either heterotopic ependymal cell rests or vestigial remnants of the distal neural tube during canalization and retrogressive differentiation (26,27).
Clinical Presentation.—As with most primary intramedullary tumors, there is frequently a long antecedent history before the diagnosis of an intramedullary ependymoma is established. The mean duration of symptoms was 36.5 months for the 183 patients from the four largest studies (5,19,24,25). A large majority of patients with spinal cord ependymomas have relatively mild clinical symptoms. Most of the 183 patients (81%) could walk without assistance at presentation (5,24,25). In general, the less preoperative neurologic deficit existing at presentation, the better the postoperative outcome (5,25). Typically, patients initially present with mild symptoms, and there is no objective evidence of neurologic deficits, which often leads to a delay in diagnosis (5,19,24,25). Some ependymomas may even be a source of subarachnoid hemorrhage (28,29).
At diagnosis, patients with spinal cord ependymomas typically have back or neck pain (67%), sensory deficits (52%), motor weakness (46%), or bowel or bladder dysfunction (15%) (5,19,24,25). The predominance of sensory symptoms (85% of patients with pain and other sensory deficits combined) may be directly related to the more central location of these tumors (5). Spinal cord ependymomas are believed to arise from ependymal cells that line the central canal. Theoretically, this central location makes it likely that the crossing spinothalamic tracts will be compressed or interrupted. Dominant motor symptoms are commonly associated with very large ependymomas and a poorer postoperative outcome secondary to the increased surgical risk associated with resection of these larger lesions (5). Hoshimaru et al (25) found that patients with a shorter duration of symptoms tended to have a better postoperative outcome. Lesions of the thoracic cord are associated with poorer surgical outcomes, perhaps because of its relatively tenuous vascular supply, compared with lesions of the cervical spinal cord. This was especially true in patients with evidence of arachnoid scarring or cord atrophy at surgery (25).
Intramedullary ependymomas are characterized by slow growth and tend to compress adjacent spinal cord tissue rather than infiltrate it. Accordingly, there is almost always a cleavage plane, which facilitates microsurgical resection, the treatment of choice (5,19,24,25). Patients frequently have worsened symptoms in the immediate postoperative period secondary to edema and possibly transient interference with spinal cord blood flow (5,25,30). Postoperative radiation therapy is reserved for recurrent disease, which is much more commonly seen in cases of subtotal resection (5,25,30). The patient's preoperative neurologic status is the most important predictor of outcome (5,19,24). Earlier surgical resection is associated with fewer and less severe neurologic deficits. Recurrence is substantially reduced when a complete gross total resection can be performed (5,19,30). The 5-year survival rate for patients with spinal cord ependymomas is approximately 82%, regardless of how severe the preoperative neurologic deficits. The 20-year survival rate, however, is much worse for patients who present with a major neurologic dysfunction (50%) than for patients with a minor neurologic impairment (33%) (19). The lungs, retroperitoneum, and lymph nodes are the most common extraspinal sites of metastatic spread (31).
Pathologic Characteristics.—Most ependymomas displace rather then infiltrate adjacent neural tissue. Because ependymomas are believed to arise from ependymal cells of the central canal within the spinal cord, symmetric cord expansion is the rule. These soft, friable, well-marginated lesions are frequently gray and have associated syringomyelia (32). Polar cysts are a common finding (62% in the study by Brotchi and Fischer [24]). True tumoral cysts are less common (22% of cases) (24). Small feeding vessels at the ventral surface are commonly noted at surgical resection (5,25). The myxopapillary variant is virtually always located along the filum terminale with occasional extension to the conus medullaris and may appear as a soft, tannish "bag" of tissue (32).
Uniform, moderately hyperchromatic nuclei are typical findings at histologic examination (Fig 4) (32). Six histologic types are recognized: cellular (the classic and most common type), papillary, clear cell, tanycytic, myxopapillary, and melanotic (the least common type) (32). Perivascular pseudorosettes are virtually required to establish the diagnosis of ependymoma but may be less conspicuous in less cellular types of ependymomas. With use of the World Health Organization (WHO) classification (24), almost all spinal cord ependymomas can be classified as either grade I or grade II. Malignant types are rare (32). Cystic degeneration is seen in 50% of cases, and hemorrhage is common (especially at the superior and inferior margins of the tumor). In contrast to intracranial ependymomas, calcification is uncommon.
View larger version (144K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 4. Photomicrograph (original magnification, x100; hematoxylin-eosin [H-E] stain) of a spinal cord ependymoma shows ependymal cells with uniform hyperchromatic nuclei arranged in perivascular pseudorosettes (arrows).
|
|
Rarely, a cord ependymoma may extend exophytically and present a diagnostic challenge (8). Ependymomas may even arise outside the CNS (sacrococcygeal region, broad ligament of the ovary). Up to one-third of these ectopically located ependymomas are associated with spina bifida occulta (33).
Results of recent investigations reveal mutations of the type 2 neurofibromatosis transcript in some cases of sporadic spinal cord ependymomas that occurred in patients without type 2 neurofibromatosis. These changes have not been observed in intracranial ependymomas and, therefore, are suggestive of a different molecular basis for ependymomas that arise in the spinal cord (34).
Imaging Characteristics.—Radiographs of patients with ependymomas may reveal scoliosis (16% of cases) or canal widening (11%) with associated vertebral body scalloping, pedicle erosion, or laminar thinning (19). Conventional myelography frequently reveals either a complete or partial block in the flow of contrast material (19). At unenhanced CT, ependymomas are either isoattenuated or slight hyperattenuated compared with the normal spinal cord (19). Ependymomas enhance intensely after intravenous administration of iodinated contrast material. CT myelography shows nonspecific cord enlargement (19).
Most spinal cord ependymomas are iso- or hypointense relative to the spinal cord on T1-weighted MR images (24,35,36). In rare cases, they may manifest as a hyperintense mass, usually secondary to the effects of hemorrhage (24,35,36). On T2-weighted images, the lesions are typically hyperintense relative to the spinal cord (35,36), although in the single largest review of spinal ependymomas, isointense tumors were as common as hyperintense tumors (24). About 20%—33% of ependymomas demonstrated the "cap sign," a rim of extreme hypointensity (hemosiderin) seen at the poles of the tumor on T2-weighted images. This finding is thought to be secondary to hemorrhage, which is common in ependymomas and other highly vascular tumors (eg, paraganglioma, hemangioblastoma) (16,35). Most cases (60%) also showed evidence of cord edema around the masses (24). The average number of vertebral segments involved with abnormal signal intensity is 3.6; however, some ependymomas may involve as many as 15 segments (19,24,25,35,36). Despite the theoretic support for cord ependymomas having a central location on the basis of the presence of ependymal cells in the central canal, only 62.5%—76% of these tumors have been reported to arise from a central location (16,35).
Cysts are a common feature, with 78%—84% of ependymomas having at least one cyst (Figs 2, 3), most of which are the nontumoral (polar) variety (24,35,36). The prevalence of tumoral cysts appears to be more variable (4%—50% of cases) (24,35,36). Syringohydromyelia is also quite variable in previously published reports, occurring in 9%—50% of cases (Fig 5) (24,36). Analysis in one published case revealed that the syringomyelia fluid had a protein content consistent with that of an exudate, which supports the hypothesis that the cavity resulted from a disruption of the blood-brain barrier (37). When the data from the three largest studies evaluating contrast enhancement on MR images are combined, the vast majority of spinal cord ependymomas (84%) enhanced to at least some degree following the intravenous administration of gadolinium-based contrast material and even more (89%) had well-defined margins on the contrast-enhanced images (Figs 2, 3) (5,24,36).
View larger version (87K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5a. Intramedullary ependymoma in a 42-year-old man with a 3-month history of neck pain and upper-extremity numbness. (a) Sagittal T1-weighted MR image shows an expanded spinal cord from C2 through T2, with associated septated syringohydromyelia (arrow). The expanded cord is slightly hyperintense relative to cerebrospinal fluid. There is a focal area of low signal intensity (arrowhead) at the caudal pole of the tumor, which is suggestive of calcification or hemosiderin deposition. (b) Sagittal T2-weighted MR image reveals a septated syringohydromyelia. The inner surface of the cyst has low signal intensity (arrowheads), which is consistent with prior hemorrhage. The mass fragmented into multiple irregular, nodular, reddish-brown masses at surgical resection. Results of histologic examination revealed ependymoma.
|
|
View larger version (97K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 5b. Intramedullary ependymoma in a 42-year-old man with a 3-month history of neck pain and upper-extremity numbness. (a) Sagittal T1-weighted MR image shows an expanded spinal cord from C2 through T2, with associated septated syringohydromyelia (arrow). The expanded cord is slightly hyperintense relative to cerebrospinal fluid. There is a focal area of low signal intensity (arrowhead) at the caudal pole of the tumor, which is suggestive of calcification or hemosiderin deposition. (b) Sagittal T2-weighted MR image reveals a septated syringohydromyelia. The inner surface of the cyst has low signal intensity (arrowheads), which is consistent with prior hemorrhage. The mass fragmented into multiple irregular, nodular, reddish-brown masses at surgical resection. Results of histologic examination revealed ependymoma.
|
|
Intraoperative US reveals ependymomas as regions of sharply defined uniform echogenicity. Cysts are easily seen with this modality (5).
Myxopapillary Ependymoma
A special variant of ependymoma, the myxopapillary ependymoma constitutes about 13% of all spinal ependymomas (38). This tumor tends to have an earlier clinical presentation (mean age, 35 years) and is more commonly seen in male patients. These mucoid tumors have a distinct predilection for the conus medullaris or filum terminale and are thought to arise from the ependymal glia of the filum terminale. Consequently, myxopapillary ependymomas are the most common neoplasm (83% of cases) in this region (38). Occasionally, they occur in the extradural space, probably arising from the coccygeal medullary vestige at the distal portion of the neural tube (39). Multiple lesions have been variably reported in about 14%—43% of cases (39).
Myxopapillary ependymomas usually manifest with lower back, leg, or sacral pain and weakness or sphincter dysfunction. Although most of these tumors are slow growing, those located near the sacrum may be more aggressive, creating large, lytic areas of bone destruction (27,40,41).
Myxopapillary ependymomas are characteristically lobulated, soft, sausage-shaped masses that are often encapsulated (38). The histologic hallmark is heterogeneity, resulting from generous mucin production and papillary zones mixed with cellular areas composed of rosettes and pseudorosettes (Fig 6) (38).
View larger version (203K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 6. Photomicrograph (original magnification, x100; H-E stain) of a myxopapillary ependymoma reveals fibrovascular cores and mucoid material (arrows) in papillary formations lined with ependymal cells.
|
|
Myxopapillary ependymomas have a nonspecific radiologic appearance and are typically isointense relative to the spinal cord on T1-weighted MR images and hyperintense on T2-weighted MR images. Hyperintensity on both T1- and T2-weighted images may be noted occasionally, a finding that reflects mucin content or hemorrhage (36). Superficial siderosis may be seen but is not specific, as it has been noted in association with other highly vascular tumors (42). Enhancement is virtually always seen after the intravenous administration of contrast material (Fig 7). The predilection of these tumors for the conus medullaris should be suggestive of the diagnosis (39).
View larger version (94K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7a. Myxopapillary ependymoma of the filum terminale in a 39-year-old man with chronic low back pain and right leg sciatica. (a) Sagittal T1-weighted MR image shows a large intradural oval mass (arrows) extending from the conus medullaris to L3. It is isointense to slightly hyperintense relative to the spinal cord. (b) Sagittal T2-weighted MR image reveals mixed signal intensity within the mass. (c) Contrast-enhanced sagittal T1-weighted MR image demonstrates intense enhancement of the lesion. (d) Intraoperative photograph demonstrates the lobulated, oval intradural mass (arrows). An attachment to the filum terminale was noted at surgical resection.
|
|
View larger version (95K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7b. Myxopapillary ependymoma of the filum terminale in a 39-year-old man with chronic low back pain and right leg sciatica. (a) Sagittal T1-weighted MR image shows a large intradural oval mass (arrows) extending from the conus medullaris to L3. It is isointense to slightly hyperintense relative to the spinal cord. (b) Sagittal T2-weighted MR image reveals mixed signal intensity within the mass. (c) Contrast-enhanced sagittal T1-weighted MR image demonstrates intense enhancement of the lesion. (d) Intraoperative photograph demonstrates the lobulated, oval intradural mass (arrows). An attachment to the filum terminale was noted at surgical resection.
|
|
View larger version (97K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7c. Myxopapillary ependymoma of the filum terminale in a 39-year-old man with chronic low back pain and right leg sciatica. (a) Sagittal T1-weighted MR image shows a large intradural oval mass (arrows) extending from the conus medullaris to L3. It is isointense to slightly hyperintense relative to the spinal cord. (b) Sagittal T2-weighted MR image reveals mixed signal intensity within the mass. (c) Contrast-enhanced sagittal T1-weighted MR image demonstrates intense enhancement of the lesion. (d) Intraoperative photograph demonstrates the lobulated, oval intradural mass (arrows). An attachment to the filum terminale was noted at surgical resection.
|
|
View larger version (97K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 7d. Myxopapillary ependymoma of the filum terminale in a 39-year-old man with chronic low back pain and right leg sciatica. (a) Sagittal T1-weighted MR image shows a large intradural oval mass (arrows) extending from the conus medullaris to L3. It is isointense to slightly hyperintense relative to the spinal cord. (b) Sagittal T2-weighted MR image reveals mixed signal intensity within the mass. (c) Contrast-enhanced sagittal T1-weighted MR image demonstrates intense enhancement of the lesion. (d) Intraoperative photograph demonstrates the lobulated, oval intradural mass (arrows). An attachment to the filum terminale was noted at surgical resection.
|
|
Subependymoma
Subependymomas represent a variant of CNS ependymomas that may also occur in the spinal cord (43–45). Originally thought to arise from the pluripotential cells of the subependymal plate (45), these tumors are now believed to have their origin from tanycytes (from the Greek word tanyos, "to stretch"), cells that bridge the pial and ependymal layers (44). Although subependymomas are most commonly found within the ventricular system of the brain, 19 cases of spinal cord subependymomas have been reported in the literature, usually in male patients (74%) and involving at least a portion of the cervical cord. The mean age at presentation is 42 years, and the mean duration of symptoms is 52 months (44). The tumor may recur after surgical resection (46).
Similar to ependymomas, these tumors produce a slowly progressive clinical course with pain as the most common symptom. Sensory and motor dysfunction are reported less frequently. Most patients (83%) in the series reported by Jallo et al (44) had atrophy of one or both distal upper extremities.
Spinal cord subependymomas are soft gray or grayish yellow masses. The lesions are typically avascular and without evidence of cystic change. At histologic examination, ependymal cells are sparsely dispersed among the predominant fibrillary astrocytes (44).
At MR imaging, they manifest with fusiform dilatation of the spinal cord with well-defined borders. Unlike other ependymomas, they are eccentrically located (Fig 8) (44). In the series of Jallo et al (44), lesions that demonstrated enhancement had sharply defined margins (50% of cases), whereas those that did not enhance had diffuse symmetric spinal cord enlargement. Edema may or may not accompany the main lesion (46). MR imaging findings are not sufficiently unique to enable the differentiation of ependymomas from subependymomas (44,46). A spinal subependymoma may manifest as an extramedullary lesion within the subarachnoid space, perhaps secondary to leptomeningeal heterotopic glial cells (46).
View larger version (84K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8a. Subependymoma of the thoracic spinal cord in a 68-year-old woman with progressive lower-extremity weakness. (a) Sagittal T1-weighted image shows ill-defined expansion (arrows) of the lower thoracic spinal cord. The mass is slightly hyperintense relative to the normal spinal cord. (b) Sagittal T2-weighted image reveals an abnormal area of high signal intensity (arrow) in the region of the mass. (c) Contrast-enhanced sagittal T1-weighted image demonstrates focal enhancement of the mass (arrow). (d) Contrast-enhanced axial T1-weighted MR image reveals the eccentric location of the enhancing mass (arrow).
|
|
View larger version (87K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8b. Subependymoma of the thoracic spinal cord in a 68-year-old woman with progressive lower-extremity weakness. (a) Sagittal T1-weighted image shows ill-defined expansion (arrows) of the lower thoracic spinal cord. The mass is slightly hyperintense relative to the normal spinal cord. (b) Sagittal T2-weighted image reveals an abnormal area of high signal intensity (arrow) in the region of the mass. (c) Contrast-enhanced sagittal T1-weighted image demonstrates focal enhancement of the mass (arrow). (d) Contrast-enhanced axial T1-weighted MR image reveals the eccentric location of the enhancing mass (arrow).
|
|
View larger version (85K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8c. Subependymoma of the thoracic spinal cord in a 68-year-old woman with progressive lower-extremity weakness. (a) Sagittal T1-weighted image shows ill-defined expansion (arrows) of the lower thoracic spinal cord. The mass is slightly hyperintense relative to the normal spinal cord. (b) Sagittal T2-weighted image reveals an abnormal area of high signal intensity (arrow) in the region of the mass. (c) Contrast-enhanced sagittal T1-weighted image demonstrates focal enhancement of the mass (arrow). (d) Contrast-enhanced axial T1-weighted MR image reveals the eccentric location of the enhancing mass (arrow).
|
|
View larger version (72K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 8d. Subependymoma of the thoracic spinal cord in a 68-year-old woman with progressive lower-extremity weakness. (a) Sagittal T1-weighted image shows ill-defined expansion (arrows) of the lower thoracic spinal cord. The mass is slightly hyperintense relative to the normal spinal cord. (b) Sagittal T2-weighted image reveals an abnormal area of high signal intensity (arrow) in the region of the mass. (c) Contrast-enhanced sagittal T1-weighted image demonstrates focal enhancement of the mass (arrow). (d) Contrast-enhanced axial T1-weighted MR image reveals the eccentric location of the enhancing mass (arrow).
|
|
Astrocytoma
Prevalence.—About one-third of all spinal cord gliomas are astrocytomas. Although they are second in prevalence to ependymomas in adults, they are the most common intramedullary tumor in children. Male patients are more commonly afflicted (58% of cases) (1,7,21,24). The mean age at presentation is 29 years (24). The most common site of involvement is the thoracic cord (67% of cases), followed by the cervical cord (49%) (7,18,24). Involvement of the entire spinal cord (holocord presentation) is common in children (up to 60% in one series) but quite rare in adults (18,24). Isolated conus medullaris involvement is seen in about 3% of cases (24). Astrocytomas are rare in the filum terminale and are rarely exophytic (Fig 9) (24).
View larger version (168K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 9. Astrocytoma in a 35-year-old woman with lower-extremity weakness and numbness. Contrast-enhanced sagittal T1-weighted MR image demonstrates an irregularly enhancing intramedullary tumor with an enhancing exophytic component (arrowheads).
|
|
Clinical Presentation.—Similar to ependymomas, spinal cord astrocytomas most commonly manifest with pain and sensory deficits (53.6% of cases). Motor dysfunction is seen in 41.4% of cases (24). Bowel and bladder deficits are uncommon (24). In the opinion of Epstein et al (5), cord astrocytomas tend to manifest with paresthesia as the sensory deficit, compared with cord ependymomas, which are characterized by dysesthetic features. Objective signs of neurologic dysfunction in lower-grade astrocytomas (grades I and II) are often absent, commonly resulting in delays in the diagnosis. Patients with high-grade lesions (grades III and IV) typically present with symptoms of shorter duration and that progress more rapidly (7,47).
The clinical presentations of young children and adults with comparable astrocytomas differ slightly. Symptoms occur sooner in young children, with a median duration of 5 months (1). Although pain and motor regression are still common, gait abnormalities (27% of cases), torticollis (27%), and scoliosis (24%) are also seen (1). In one series, in patients with holocord involvement, the location of the solid portion of the lesion corresponded with the clinical symptoms (ie, cervical cord location was associated with upper-extremity deficits) (18). These tumors tend to be low-grade astrocytomas, which are characterized by slow growth and low recurrence rates (1). In fact, cord astrocytomas in children tend to behave much like grade I cerebellar pilocytic astrocytomas and displace neural tissue rather than infiltrate it (30). In a review of 100 children with either low-grade astrocytomas or gangliogliomas treated with radical surgery, 95% of patients were alive at 5 years and 80% had a disease-free interval (7). In contrast, more severe neurologic deficit at presentation, hydrocephalus, and leptomeningeal spread of disease were more common in 19 patients with high-grade cord astrocytomas described by Cohen et al (47) than in patients with low-grade tumors. Hydrocephalus alone may be indicative of leptomeningeal spread in the postoperative setting (48).
Adult patients with astrocytomas fare worse than those with cord ependymomas in terms of survival. In Cooper's study of 51 patients with intramedullary spinal cord tumors (30), 11 of 14 (79%) deaths were secondary to astrocytomas. Seven of those 11 patients had high-grade (grade III or IV) astrocytomas and four had low-grade tumors.
Unlike the findings seen in patients with cord ependymomas, the amount of resected astrocytoma did not have an effect on survival. Even in cases of gross total resection, patients with astrocytomas had much higher mortality rates than those with comparable cord ependymomas (30). The poorer prognosis is likely a reflection of the infiltrative nature of astrocytomas for two reasons. First, neoplastic astrocytes extend far beyond the apparent gross tumor margin and provide a source of tumor progression postoperatively. Second, because the malignant cells may extend along the network of normal axonal processes, removal of neoplastic tissue invariably will also necessitate resection of normal functioning cord tissue, which increases the likelihood of postoperative neurologic deficits. There are divergent opinions in the neurosurgical literature about the management of these cases. Some advocate attempts at gross total resection (24), whereas others recommend an initial biopsy of the enlarged cord. If a high-grade astrocytoma is seen at frozen section analysis, tumor debulking is performed. However, knowing that some malignant cells will remain despite gross macroscopic removal and because attempts at gross total resection carry such a high potential for neurologic morbidity, gross total resection is not necessarily a goal in treating these tumors, and radiation therapy is administered in an attempt to eradicate residual disease (30,49). At least one investigator recommends yearly follow-up MR imaging in all adult patients with cord astrocytomas (30).
Pathologic Characteristics.—At gross inspection, spinal cord astrocytomas are characterized by ill-defined diffuse fusiform enlargement. In contrast to cord ependymomas, a cleavage plane is often not present in most intramedullary spinal astrocytomas (24). Tumor cysts (which are frequently eccentric, smaller, and irregular in shape compared with benign cysts) and syrinxes are common, especially in pilocytic types (32).
All astrocytomas are characterized by hypercellularity and the absence of a surrounding capsule. Accordingly, neoplastic astrocytes will extend along the "scaffold" of normal astrocytes, oligodendrocytes, and axons of the surrounding neural tissue in an infiltrative pattern (32). As a result, astrocytomas are never circumscribed despite an occasional imaging appearance that may suggest otherwise. Enlarged, irregularly shaped, hyperchromatic nuclei are virtually always present at histologic examination.
In general, the amount and degree of pleomorphism correlates with the biologic behavior of these tumors. In the WHO classification, four basic grades of astrocytomas are recognized. Grade I lesions correspond to pilocytic astrocytomas, are commonly seen in the cerebellum (cerebellar cystic astrocytomas), and have the most benign biologic behavior of all the other types. Grade II tumors are of the fibrillary type and are the classic low-grade astrocytoma (Fig 10). Grade III lesions, or anaplastic astrocytomas, contain more pleomorphism, less differentiation, even more hypercellularity, and regions of necrosis compared with the lower-grade lesions. Grade IV lesions, or glioblastoma multiforme, are the most malignant type of astrocytoma and show evidence of endothelial proliferation at microscopic review (Fig 11) (32). Although grade IV lesions make up half of all brain astrocytomas, they are distinctly uncommon in the spinal cord. Only 0.2—1.5% of spinal cord astrocytomas are grade IV lesions. Instead, the well-differentiated grade I astrocytoma (also including gemistocytic and protoplasmic variants) accounts for 75% of cord astrocytomas. Up to 25% of astrocytomas are classified as grade III (anaplastic) lesions. In children younger than 3 years, most cord astrocytomas (80%) are low-grade (either grade I or II) fibrillary types. The remainder are divided between anaplastic (grade III) astrocytomas, glioblastoma multiforme (grade IV), and mixed oligoastrocytomas (1).
View larger version (201K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 10. Photomicrograph (original magnification, x100; H-E stain) of a spinal cord astrocytoma reveals increased cellularity with mild nuclear pleomorphism. The lack of mitotic activity, endothelial proliferation, and necrosis supports the histologic diagnosis of a grade II astrocytoma.
|
|
View larger version (178K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11a. (a) Photomicrograph (original magnification, x200; H-E stain) of a spinal cord glioblastoma multiforme demonstrates a hypercellular pleomorphic neoplasm with endothelial proliferation (arrows). (b) Photomicrograph (original magnification, x100; H-E stain) of a different field in the same tumor shows zones of necrosis (n) and mitotic activity (arrowhead).
|
|
View larger version (180K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 11b. (a) Photomicrograph (original magnification, x200; H-E stain) of a spinal cord glioblastoma multiforme demonstrates a hypercellular pleomorphic neoplasm with endothelial proliferation (arrows). (b) Photomicrograph (original magnification, x100; H-E stain) of a different field in the same tumor shows zones of necrosis (n) and mitotic activity (arrowhead).
|
|
Imaging Characteristics.—Mild scoliosis, widened interpedicular distance, and bone erosion may be seen at conventional radiography and CT, but these signs occur less commonly in astrocytomas than they do in ependymomas. Patients with holocord involvement tend to present with scoliosis and canal widening (18). At MR imaging, these neoplasms usually have poorly defined margins and are iso- to hypointense relative to the spinal cord on T1-weighted images and hyperintense on T2-weighted images. The average length of involvement is seven vertebral segments. Cysts are a common feature, with both polar and intratumoral types being observed (Fig 12) (1). Virtually all cord astrocytomas show at least some enhancement following the intravenous administration of contrast material (1). The cap sign is not associated with cord astrocytomas (16). Because astrocytomas arise from the cord parenchyma and not from the central canal, they are usually (57% of cases) eccentric within the cord (Fig 13) (16). Leptomeningeal spread is seen in 60% of intramedullary glioblastoma multiformes (47,50). At transverse imaging, intraoperative US reveals asymmetric expansion of the spinal cord with variable echogenicity. Frequently, the lesion is virtually isoechoic relative to the normal spinal cord (17).
View larger version (90K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12a. Intramedullary mixed glioma in a 27-year-old man who presented with neck pain and numbness in his left hand, hiccups, and difficulty in swallowing. (a) Sagittal T1-weighted MR image shows an intramedullary, slightly hyperintense, heterogeneous mass of the upper cervical spinal cord extending into the medulla. There is a cystlike area with a fluid-fluid level (arrow). (b) Sagittal T2-weighted MR image reveals a heterogeneous intramedullary lesion and a brainstem cyst containing a fluid-fluid level. A curvilinear, low-signal-intensity area within the cord (arrow) is suggestive of hemorrhage. Cord edema (arrowheads) is evident inferior to the mass. The image plane is slightly lateral to that shown in a.
|
|
View larger version (105K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 12b. Intramedullary mixed glioma in a 27-year-old man who presented with neck pain and numbness in his left hand, hiccups, and difficulty in swallowing. (a) Sagittal T1-weighted MR image shows an intramedullary, slightly hyperintense, heterogeneous mass of the upper cervical spinal cord extending into the medulla. There is a cystlike area with a fluid-fluid level (arrow). (b) Sagittal T2-weighted MR image reveals a heterogeneous intramedullary lesion and a brainstem cyst containing a fluid-fluid level. A curvilinear, low-signal-intensity area within the cord (arrow) is suggestive of hemorrhage. Cord edema (arrowheads) is evident inferior to the mass. The image plane is slightly lateral to that shown in a.
|
|
View larger version (125K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13a. Intramedullary glioblastoma multiforme in a 14-year-old boy who presented with neck pain. (a) Sagittal T1-weighted MR image shows irregular expansion of the cervical spinal cord extending from C3 to C7 (arrows). The affected cord is slightly hypointense relative to the unaffected cord. Note expansion of the spinal canal secondary to bony remodeling. (b) Sagittal T2-weighted MR image reveals an abnormal area of high signal intensity throughout the expanded region. (c) Contrast-enhanced sagittal T1-weighted MR image displays irregular, intense, homogeneous enhancement of the inferior portion of the expanded cord from C5 through T1 (arrows). (d) Axial gradient-echo MR image demonstrates expansion of the cord with the mass eccentrically located along its right margin (arrows).
|
|
View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13b. Intramedullary glioblastoma multiforme in a 14-year-old boy who presented with neck pain. (a) Sagittal T1-weighted MR image shows irregular expansion of the cervical spinal cord extending from C3 to C7 (arrows). The affected cord is slightly hypointense relative to the unaffected cord. Note expansion of the spinal canal secondary to bony remodeling. (b) Sagittal T2-weighted MR image reveals an abnormal area of high signal intensity throughout the expanded region. (c) Contrast-enhanced sagittal T1-weighted MR image displays irregular, intense, homogeneous enhancement of the inferior portion of the expanded cord from C5 through T1 (arrows). (d) Axial gradient-echo MR image demonstrates expansion of the cord with the mass eccentrically located along its right margin (arrows).
|
|
View larger version (121K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13c. Intramedullary glioblastoma multiforme in a 14-year-old boy who presented with neck pain. (a) Sagittal T1-weighted MR image shows irregular expansion of the cervical spinal cord extending from C3 to C7 (arrows). The affected cord is slightly hypointense relative to the unaffected cord. Note expansion of the spinal canal secondary to bony remodeling. (b) Sagittal T2-weighted MR image reveals an abnormal area of high signal intensity throughout the expanded region. (c) Contrast-enhanced sagittal T1-weighted MR image displays irregular, intense, homogeneous enhancement of the inferior portion of the expanded cord from C5 through T1 (arrows). (d) Axial gradient-echo MR image demonstrates expansion of the cord with the mass eccentrically located along its right margin (arrows).
|
|
View larger version (136K):
[in this window]
[in a new window]
[Download PPT slide]
|
Figure 13d. Intramedullary glioblastoma multiforme in a 14-year-old boy who presented with neck pain. (a) Sagittal T1-weighted MR image shows irregular expansion of the cervical spinal cord extending from C3 to C7 (arrows). The affected cord is slightly hypointense relative to the unaffected cord. Note expansion of the spinal canal secondary to bony remodeling. (b) Sagittal T2-weighted MR image reveals an abnormal area of high signal intensity throughout the expanded region. (c) Contrast-enhanced sagittal T1-weighted MR image displays irregular, intense, homogeneous enhancement of the inferior portion of the expanded cord from C5 through T1 (arrows). (d) Axial gradient-echo MR image demonstrates expansion of the cord with the mass eccentrically located along its right margin (arrows).
|
|
A summary of the salient features of spinal cord ependymomas and astrocytomas is provided in Table 2.
Ganglioglioma
Prevalence.—Gangliogliomas account for 0.4%—6.25% of all primary CNS tumors and about 1.1% of all spinal neoplasms (51). They are more common in children than in adults, with 19 years of age being the mean age of presentation (51). There is no gender predilection (51,52). Within the CNS, most gangliogliomas are located supratentorially, primarily arising in the temporal lobe. In rare cases, they may extend into the cervical spinal cord from the cerebellum (53). In a review of 22 spinal cord tumors with a known location, there was near-equal distribution between the cervical and thoracic regions (51). Patel et al (52) reported that almost half of their 27 cases (48%) arose within the cervical cord, with the thoracic cord a distant second (22%). Less commonly, gangliogliomas may involve the conus medullaris or the entire spinal cord (holocord) (51,52). They are commonly eccentric in location and contain tumoral cysts even more often (46% of cases) than do spinal astrocytomas (20%) and ependymomas (3%) (51,52).
Clinical Presentation.—As with ependymomas, gangliogliomas are characterized by slow growth and a good prognosis. Rarely, malignant forms may occur and disseminate through the CNS (54). There is a wide range in duration of symptoms (1 month to 5 years) (51). Although the potential for malignancy is low, spinal cord gangliogliomas have a recurrence rate of 27%, which is about three to four times that of cerebral gangliogliomas (51). Overall, patients with spinal gangliogliomas have a 5-year survival rate of 89% and a 10-year survival rate of 83% (51).
Pathologic Characteristics.—True to their name, gangliogliomas represent a mixture of mature but neoplastic neuronal elements (neurons or ganglion cells) and glial elements (primarily neoplastic astrocytes) at histologic examination (Fig 14). Because the proportions of cells may vary from tumor to tumor, various synonyms have been used to describe these lesions, including ganglioglioneuroma, ganglionic neuroma, neuroastrocytoma, neuroganglioma, ganglionic glioma, neuroma gangliocellulare, and neuroglioma (52). The neuronal cells are typically irregularly oriented and arranged in clusters. As with normal neuronal cells, the neoplastic neuronal cells in spinal cord gangliogliomas demonstrate immunopositivity for synaptophysin. Other immunohistochemical stains (neurofilament protein, neuron-specific enolase, and chromogranin A) are also frequently positive. Nonspecific histologic features (Rosenthal fibers, eosinophilic granular bodies) are common (51). Accordingly, these tumors are classified as grade I or II lesions in the WHO system. Calcification and small cysts are common (55). Malignant transformation in CNS gangliogliomas has been reported in the literature (about 10% of cases) and may be related to prior irradiation (54). There are no histologic markers that enable the prediction of biologic behavior (51). It is speculated by some that spinal gangliogliomas have been underdiagnosed in the past, being labeled as astrocytomas or other tumors (52). However, not all investigators share this opinion (56).
Top
Abstract
LEARNING OBJECTIVES FOR TEST...
