DOI: 10.1148/rg.234025176
(Radiographics. 2003;23:995-1009.)
© RSNA, 2003
Comprehensive Review of Intracranial Chordoma1
Eren Erdem, MD,
Edgardo C. Angtuaco, MD,
Rudy Van Hemert, MD,
Jong S. Park, MD and
Ossama Al-Mefty, MD
1 From the Departments of Radiology (E.E., E.C.A., R.V.H., J.S.P.) and Neurosurgery (O.A.M.), University of Arkansas for Medical Sciences, 4501 W Markham St, Little Rock, AR 72205. Presented as an education exhibit at the 2001 RSNA scientific assembly. Received December 18, 2002; revision requested February 20, 2003 and received March 26; accepted March 31. Address correspondence to E.E. (e-mail: erenmri@yahoo.com).
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Abstract
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Intracranial chordoma is a locally aggressive and relatively rare tumor of the skull base that is thought to originate from embryonic remnants of the primitive notochord. Both computed tomography (CT) and magnetic resonance (MR) imaging are usually required for evaluation of intracranial chordomas due to bone involvement and the proximity of these tumors to many critical soft-tissue structures. At CT, intracranial chordoma typically appears as a centrally located, well-circumscribed, expansile soft-tissue mass that arises from the clivus with associated extensive lytic bone destruction. However, MR imaging is the single best imaging modality for both pre- and posttreatment evaluation of intracranial chordoma. On T1-weighted MR images, intracranial chordomas demonstrate intermediate to low signal intensity and are easily recognized within the high-signal-intensity fat of the clivus. On T2-weighted MR images, they characteristically demonstrate very high signal intensity, a finding that likely reflects the high fluid content of vacuolated cellular components. Moderate to marked enhancement is common and often heterogeneous on contrast material–enhanced images. Combination treatment with radical surgical resection and proton beam radiation therapy achieves the best results.
© RSNA, 2003
Index Terms: Chordoma, 12.327 • Skull, CT, 12.1211 • Skull, MR, 12.1214 • Skull, primary neoplasms, 12.327
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LEARNING OBJECTIVES FOR TEST 6
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After reading this article and taking the test, the reader will be able to:
- Recognize the important CT and MR imaging features of intracranial chordomas.
- Identify the common locations and areas of extension of intracranial chordomas.
- Describe the embryonic origin, clinical manifestations, and histopathologic features of intracranial chordomas.
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Introduction
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Chordomas are relatively rare malignant tumors that arise from embryonic remnants of the primitive notochord, a primitive cell line around which the skull base and the vertebral column develop. Remnants of the notochord usually remain in or close to the midline, entrapped within bone. Chordomas are considered locally invasive, but they rarely metastasize (1–3). Chordomas account for 1% of intracranial tumors and 4% of all primary bone tumors (4). They may occur at any age but are usually seen in adults, with a peak prevalence in the 4th decade of life. Chordomas have a 2:1 male predilection and affect whites more than blacks (1,2,5,6). Intracranial chordomas constitute one-third of all chordomas and usually occur in the vicinity of the clivus (spheno-occipital bones). Although intracranial chordomas are generally slow growing, their intimate relation to critical structures and extremely high local recurrence rate have often resulted in high mortality rates in the past. However, recent advances in skull base surgery and radiation therapy now provide the opportunity for cure (7,8). The excellent imaging capabilities of magnetic resonance (MR) imaging and computed tomography (CT) allow precise delineation of the tumors with respect to volume and relation to adjacent neural structures, thereby helping achieve this cure (9). Therefore, familiarity with the radiologic features of intracranial chordomas is crucial.
In this article, we review the clinical features, location, histopathologic features, imaging characteristics, patterns of spread, treatment, recurrence and metastasis, and differential diagnosis of intracranial chordoma.
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Clinical Features
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Generally, chordomas grow slowly and produce symptoms insidiously. Symptoms of intracranial chordomas vary with lesion location and proximity to critical structures, reflecting the specific sites of extension from the clivus (ie, the sellar, parasellar, and retroclival areas and, occasionally, the sphenoid sinus). The most common initial complaint is diplopia related to cranial nerve palsy and headache. Among cranial nerves, the abducent nerve is the most commonly affected. Headache is usually reported in an occipital or retro-orbital location (5,10–13).
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Location
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Chordomas may occur at any site along the course of the embryonic notochord. In a recent review of 400 patients with chordoma, McMaster et al (2) found that the chordomas were relatively evenly distributed along the cranial (32%), spinal (32.8%), and sacral (29.2%) portions of the axial skeleton. Intracranial chordomas most often originate from the spheno-occipital synchondrosis of the clivus. The site of origin may be along the upper clivus (basisphenoid) or along the caudal margin of the clivus (basiocciput) (Fig 1). Occasionally, intracranial chordomas may arise unilaterally from the petrous apex, a finding that was seen in up to 15% of cases in one series (14). This finding is most likely the result of multiplying cells of the notochord penetrating the skull base from different directions during the early embryonic stage. Remnants of these notochordal branches that have penetrated the developing petrous bone presumably provide the seed from which a subsequent petrous chordoma may grow (14,15). Other sites of origin include the sellar area, sphenoid sinus, and, rarely, the nasopharynx (16), maxilla (17), paranasal sinuses, or intradural region (18).
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Figure 1a. (a) Three-dimensional CT scan demonstrates the sites of origin of intracranial chordomas: the upper (yellow), middle (red), and lower (green) clivus. (b-d) Sagittal T1-weighted MR images demonstrate involvement of the upper (b), middle (c), and lower (d) clivus.
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Figure 1b. (a) Three-dimensional CT scan demonstrates the sites of origin of intracranial chordomas: the upper (yellow), middle (red), and lower (green) clivus. (b-d) Sagittal T1-weighted MR images demonstrate involvement of the upper (b), middle (c), and lower (d) clivus.
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Figure 1c. (a) Three-dimensional CT scan demonstrates the sites of origin of intracranial chordomas: the upper (yellow), middle (red), and lower (green) clivus. (b-d) Sagittal T1-weighted MR images demonstrate involvement of the upper (b), middle (c), and lower (d) clivus.
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Figure 1d. (a) Three-dimensional CT scan demonstrates the sites of origin of intracranial chordomas: the upper (yellow), middle (red), and lower (green) clivus. (b-d) Sagittal T1-weighted MR images demonstrate involvement of the upper (b), middle (c), and lower (d) clivus.
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Histopathologic Features
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At gross examination, chordomas appear as gelatinous, multilobulated, semitranslucent grayish tumors. The majority of lesions are 2–5 cm in size (19). Chordomas have been divided into two histopathologic subtypes: typical chordomas and chondroid chordomas. In typical chordomas, the cells tend to be arranged in cords set in a pale matrix of mucopolysaccharide with a characteristic physaliphorous appearance (Fig 2) (10). In addition, typical chordomas contain areas of necrosis, recent and old hemorrhage, and entrapped bone trabeculae. Mitoses are infrequent, even in specimens from recurrent or metastasized chordomas (1). In chondroid chordomas, the stroma resembles hyaline cartilage with neoplastic cells in lacunae. This variant is more commonly seen in the skull base, constituting up to one-third of cases in that region, and usually has a better prognosis (1,20). Chondroid chordomas may resemble low-grade chondrosarcomas. With the help of immunohistochemical studies, these tumors can be identified on the basis of elements (epithelial markers) that indicate their relation to notochordal mesenchyma (5).
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Figure 2. Photomicrograph (original magnification, x400; hematoxylin-eosin stain) shows vacuolated cells with intracytoplasmic mucus droplets (physaliphorous appearance) (arrows), a finding that is typical of chordoma.
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Imaging Characteristics
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Radiologic evaluation of intracranial chordomas has improved with the advent of CT and MR imaging. Diagnostic characteristics are now better defined, and tumor extension in the skull base can be demonstrated with precision. These capabilities are crucial for both the surgeon, who is planning radical resection of the tumor, and the radiation oncologist, who demarcates the tumor margins, neighboring cranial nerves, and vital vascular structures for further therapy. Both CT and MR imaging are usually required for pretreatment evaluation.
High-Resolution CT
High-resolution CT with a bone and soft-tissue algorithm has proved to be sensitive for detecting lesions of the skull base. Thin-section axial and coronal unenhanced and contrast material–enhanced images are usually obtained for assessment. CT is very accurate in the depiction of bone abnormalities; however, due to beam-hardening artifacts, it is somewhat limited in its capacity to show soft-tissue structures in the posterior fossa (21).
The classic appearance of intracranial chordoma at high-resolution CT is that of a centrally located, well-circumscribed, expansile soft-tissue mass that arises from the clivus with associated extensive lytic bone destruction. The bulk of the tumor is usually hyperattenuating relative to the adjacent neural axis. Intratumoral calcifications appear irregular at CT and are usually thought to represent sequestra from bone destruction rather than dystrophic calcifications in the tumor itself (Fig 3). The chondroid variant is more likely to demonstrate real intratumoral calcifications (Fig 4). There is moderate to marked enhancement following administration of iodinated contrast material. Solitary or multiple low-attenuation areas are sometimes seen within the soft-tissue mass and probably represent the myxoid and gelatinous material seen at gross examination (21,22).
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Figure 3a. (a) Sagittal reformatted CT scan reveals bone sequestra at the distal end of a lytic clival lesion (arrows). (b) Axial CT scan of the skull base demonstrates the lesion with a clival origin and extension to the prepontine cistern with typical trabecular entrapment (arrow). Dystrophic calcification is also seen (arrowhead).
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Figure 3b. (a) Sagittal reformatted CT scan reveals bone sequestra at the distal end of a lytic clival lesion (arrows). (b) Axial CT scan of the skull base demonstrates the lesion with a clival origin and extension to the prepontine cistern with typical trabecular entrapment (arrow). Dystrophic calcification is also seen (arrowhead).
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MR Imaging
MR imaging is the single best modality for radiologic evaluation of intracranial chordomas (23). MR imaging is the equal of CT in detecting intracranial chordomas. However, it is considerably superior to CT in the delineation of lesion extent because it provides excellent tissue contrast and exquisite anatomic detail (24). The multiplanar capability of MR imaging is also helpful in this regard. Sagittal images are generally the most valuable in defining the posterior margin of the tumor, showing the relation between the tumor and brainstem, and depicting nasopharyngeal extension of the tumor. Sagittal imaging is also useful in disclosing transdural transgression by a tumor, an important factor in surgical planning. Coronal images, on the other hand, are helpful in detecting tumor extension into the cavernous sinus and depicting the position of the optic chiasm and tract (9,25).
MR imaging is deficient only in the evaluation of calcification and cortical bone (23). Because it has a paucity of mobile protons, cortical bone manifests as an area of low signal intensity with all sequences. Osseous destruction is implied by replacement of the signal void of cortical bone with the soft-tissue signal intensity of tumor. There can still be problems in making this determination in the skull base. The definition of fine cortical structures such as the carotid canal wall is limited. In addition, soft tissues adjacent to a thin bone can demonstrate enough signal intensity that a signal void is not present, resulting in an erroneous picture of cortical involvement. Use of contrast-enhanced imaging can solve this problem if the tissue on the opposite side of the bone (eg, dura mater) shows abnormal enhancement, which confirms bone involvement even though the cortex is not actually visualized.
On conventional spin-echo T1-weighted MR images, intracranial chordoma has intermediate to low signal intensity and is easily recognized within the high signal intensity of the fat of the clivus (Fig 5). Small foci of hyperintensity can sometimes be visualized in the tumor on T1-weighted images, a finding that represents intratumoral hemorrhage or a mucus pool (Fig 6) (26). The presence of hemorrhagic foci can be confirmed with gradient-echo imaging that is susceptible to blood, at which the foci appear as dark areas. Classic intracranial chordoma has high signal intensity on T2-weighted images (Fig 7), a finding that likely reflects the high fluid content of vacuolated cellular components. The intratumoral areas of calcification, hemorrhage, and a highly proteinaceous mucus pool usually demonstrate heterogeneous hypointensity at T2-weighted imaging (Fig 8). Low-signal-intensity septations that separate high-signal-intensity lobules are commonly seen (Fig 9), corresponding to the multilobulated gross morphologic features of the tumor. Also, T2-weighted imaging is excellent for differentiating tumor from adjacent neural structures (9).
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Figure 5a. (a) Axial T1-weighted MR image shows a small, hypointense mass in the right side of the clivus (arrow). (b) Sagittal T1-weighted MR image obtained in a different patient shows a large, hypointense soft-tissue mass that arises from the distal clivus with anterior extension into the nasopharynx (arrows) and extradural extension into the posterior fossa (arrowhead).
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Figure 5b. (a) Axial T1-weighted MR image shows a small, hypointense mass in the right side of the clivus (arrow). (b) Sagittal T1-weighted MR image obtained in a different patient shows a large, hypointense soft-tissue mass that arises from the distal clivus with anterior extension into the nasopharynx (arrows) and extradural extension into the posterior fossa (arrowhead).
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Figure 6. Sagittal T1-weighted MR image shows a retroclival mass (arrows) that has a hyperintense rim and projects posteriorly, a finding that represents highly proteinaceous material or blood products.
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Figure 8. Axial T2-weighted MR image demonstrates a multiseptate, hyperintense mass with extension into the sellar area and left cavernous sinus. The mass also exhibits areas of hypointensity, possibly secondary to calcification, hemorrhage, or a mucus collection.
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The majority of intracranial chordomas demonstrate moderate to marked enhancement following contrast material injection (Fig 10). Occasionally, the enhancement is slight or even absent (Fig 11). Such a finding likely represents necrosis and a large amount of mucinous material in the tumor. The enhancement pattern of the tumor sometimes has a "honeycomb" appearance created by intratumoral areas of low signal intensity (Fig 12) (27). Fat suppression is useful for differentiating enhanced tumor margins from adjacent bright fatty bone marrow. In addition, small intraclival chordomas can be better demarcated with this technique.
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Figure 10a. (a) Axial unenhanced T1-weighted MR image shows an isointense mass along the right side of the clivus and petrous apex. (b) Axial contrast-enhanced T1-weighted MR image shows the mass with marked enhancement.
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Figure 10b. (a) Axial unenhanced T1-weighted MR image shows an isointense mass along the right side of the clivus and petrous apex. (b) Axial contrast-enhanced T1-weighted MR image shows the mass with marked enhancement.
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Figure 11a. (a) Sagittal unenhanced T1-weighted MR image shows a large, isointense soft-tissue mass in the distal clivus (arrows). (b) On a sagittal contrast-enhanced T1-weighted MR image, the mass exhibits little or no enhancement (arrows). Note the normal enhancement of the nasal, nasopharyngeal, and palatal mucosa.
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Figure 11b. (a) Sagittal unenhanced T1-weighted MR image shows a large, isointense soft-tissue mass in the distal clivus (arrows). (b) On a sagittal contrast-enhanced T1-weighted MR image, the mass exhibits little or no enhancement (arrows). Note the normal enhancement of the nasal, nasopharyngeal, and palatal mucosa.
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Figure 12. Axial contrast-enhanced T1-weighted MR image shows a large midclival mass with variable enhancement (honeycomb appearance) and extension to the sellar area and adjacent cavernous sinuses. Note the lateral displacement of the right cavernous internal carotid artery (arrow).
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Sze et al (25) reported that because a watery, gelatinous matrix is replaced by cartilaginous foci, chondroid chordomas have shorter T1 and T2 values than do typical chordomas. Therefore, chondroid chordomas may not be as bright as typical chordomas on T2-weighted MR images. This finding is an important prognostic factor due to the significantly better survival rate of patients with chondroid chordoma.
MR Angiography and Conventional Angiography
A clear advantage of MR imaging is its capacity to demonstrate patent major vessels as flow voids. The internal carotid and basilar arteries and their anatomic relationship to tumors are well visualized in most intracranial chordomas. Tumoral displacement or partial encasement of intracranial arteries is common, being visualized in up to 79% of intracranial chordomas (Fig 13) (26). Despite the high frequency of intracranial arterial involvement, arterial narrowing is rare in intracranial chordomas (Fig 14), a finding that reflects the fact that these tumors are generally soft and easily dissected from adjacent vessels. Therefore, MR angiography allows better evaluation of vascular encasement and obviates cerebral angiography, which does not allow detection of encasement without luminal narrowing or occlusion (28). Venous involvement or occlusion is also readily visualized at MR venography.
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Figure 13a. (a) Sagittal T1-weighted MR image demonstrates posterior and superior elevation of the right cavernous internal carotid artery (arrows). (b) Composite MR angiogram obtained in a different patient shows posterior displacement of the right posterior cerebral artery (arrowhead) and lateral displacement of the right cavernous carotid artery (arrow). (c) Coronal T1-weighted MR image obtained in a third patient shows a tumor with extension to the right cavernous sinus and concomitant displacement and partial encasement of the right cavernous internal carotid artery (arrow).
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Figure 13b. (a) Sagittal T1-weighted MR image demonstrates posterior and superior elevation of the right cavernous internal carotid artery (arrows). (b) Composite MR angiogram obtained in a different patient shows posterior displacement of the right posterior cerebral artery (arrowhead) and lateral displacement of the right cavernous carotid artery (arrow). (c) Coronal T1-weighted MR image obtained in a third patient shows a tumor with extension to the right cavernous sinus and concomitant displacement and partial encasement of the right cavernous internal carotid artery (arrow).
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Figure 13c. (a) Sagittal T1-weighted MR image demonstrates posterior and superior elevation of the right cavernous internal carotid artery (arrows). (b) Composite MR angiogram obtained in a different patient shows posterior displacement of the right posterior cerebral artery (arrowhead) and lateral displacement of the right cavernous carotid artery (arrow). (c) Coronal T1-weighted MR image obtained in a third patient shows a tumor with extension to the right cavernous sinus and concomitant displacement and partial encasement of the right cavernous internal carotid artery (arrow).
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Figure 14a. (a) Sagittal contrast-enhanced T1-weighted MR image shows a large, irregularly enhancing mass (arrow) with retroclival extension that encases the left internal carotid artery (arrowhead). (b) Left carotid arteriogram shows narrowing of the distal left internal carotid artery (arrow) and upward displacement of the left middle cerebral artery (arrowhead).
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Figure 14b. (a) Sagittal contrast-enhanced T1-weighted MR image shows a large, irregularly enhancing mass (arrow) with retroclival extension that encases the left internal carotid artery (arrowhead). (b) Left carotid arteriogram shows narrowing of the distal left internal carotid artery (arrow) and upward displacement of the left middle cerebral artery (arrowhead).
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Angiographic evaluation of intracranial chordomas is nonspecific. Abnormal tumor vascularity or staining is rare (Fig 15) (29,30). Angiographic evaluation is reserved for cases in which there is significant displacement, encasement, or narrowing of the internal carotid or vertebral artery at MR angiography. Cerebral angiography can better demonstrate the degree of luminal narrowing or occlusion and the extent of collateral circulation. Temporary balloon occlusion of the internal carotid artery is frequently used to determine whether patients are at risk for neurologic injury during surgery due to permanent vessel occlusion (26).
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Figure 15a. (a) Sagittal T1-weighted MR image shows a mass that involves the posterior fossa (arrows) with extracranial soft-tissue extension to the face. (b) Left external carotid arteriogram demonstrates recurrent tumor with vasculature from the branches of the posterior auricular artery (arrow). Note the occlusion of the internal carotid artery (arrowhead).
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Figure 15b. (a) Sagittal T1-weighted MR image shows a mass that involves the posterior fossa (arrows) with extracranial soft-tissue extension to the face. (b) Left external carotid arteriogram demonstrates recurrent tumor with vasculature from the branches of the posterior auricular artery (arrow). Note the occlusion of the internal carotid artery (arrowhead).
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Tumor Spread
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The classic midline clival chordoma can spread anteriorly (Fig 16), laterally (Fig 17), posteriorly (Fig 18), inferiorly (Fig 19), and superiorly (Fig 20), thereby affecting the sellar area, petrous apex–middle cranial fossa, prepontine cistern, foramen magnum–nasopharynx, and chiasm–third ventricle, respectively. Usually more than one of these areas is involved. Anterior tumor extension can involve the sphenoid sinus and, less commonly, the posterior ethmoid sinus. Anteroinferior extension can affect the nasopharynx and parapharyngeal space. Posteroinferior extension leads to involvement of the jugular fossa and foramen magnum, with erosion of the atlas and other cervical vertebrae. Intracranial chordomas may arise in the sellar and parasellar areas. Lateral extension of these tumors can invade the middle cranial fossa, whereas posterior extension can affect the petrous apex. Intracranial chordomas can grow into the basal cisterns with compression of the brainstem. In addition, intracranial chordomas commonly encroach on the anterior visual pathway and on the cranial nerves in the prepontine cistern and cavernous sinus, resulting in visual and cranial nerve abnormalities.
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Figure 16a. Anterior extension. (a) Sagittal T1-weighted MR image shows a lesion that involves the sphenoid sinus (arrows). (b) Coronal T1-weighted MR image shows orbital involvement by the lesion, with greater involvement on the left side (arrow) than on the right (arrowhead).
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Figure 16b. Anterior extension. (a) Sagittal T1-weighted MR image shows a lesion that involves the sphenoid sinus (arrows). (b) Coronal T1-weighted MR image shows orbital involvement by the lesion, with greater involvement on the left side (arrow) than on the right (arrowhead).
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Figure 17a. Lateral extension. (a) Coronal contrast-enhanced T1-weighted MR image demonstrates bilateral involvement of the cavernous sinuses (arrows), with more involvement on the left side than on the right. (b) Axial contrast-enhanced T1-weighted MR image demonstrates involvement of the middle cranial fossa (arrows).
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Figure 17b. Lateral extension. (a) Coronal contrast-enhanced T1-weighted MR image demonstrates bilateral involvement of the cavernous sinuses (arrows), with more involvement on the left side than on the right. (b) Axial contrast-enhanced T1-weighted MR image demonstrates involvement of the middle cranial fossa (arrows).
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Treatment
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Surgical removal is a very effective treatment for intracranial chordomas. Longer survival rates have been associated with more extensive tumor removal (8). With advances in imaging technology, presurgical evaluation can now provide more detailed knowledge of the lesion and suggest the best surgical approach. In addition, new, aggressive techniques of skull base surgery allow radical total resection with sparing of vital structures in an increasing number of cases.
Extension through the skull base, which is a distinguishing feature of skull base chordomas, is still the main limiting factor in their complete surgical removal and the cause for frequent multiple surgical approaches, although complete surgical removal is still achievable with acceptably low morbidity and mortality rates. A cranio-orbitozygomatic approach is the most versatile method for lesions that are centered in the upper clivus and extend laterally (Fig 21). A transcondylar approach is used to reach intracranial chordomas located at the inferior clivus, and a transmaxillary approach is used for lesions that extend from the clivus into the nasopharynx (Fig 22) or craniocervical junction (8,11). With these techniques, radical or subtotal removal of intracranial chordomas can be achieved in nearly 90% of cases (8).
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Figure 21a. (a) Presurgical axial contrast-enhanced T1-weighted MR image shows a tumor that involves the posterior fossa (arrow). (b) Axial contrast-enhanced T1-weighted MR image obtained after surgery (cranio-orbitozygomatic approach) shows complete resection of the tumor (arrows).
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Figure 21b. (a) Presurgical axial contrast-enhanced T1-weighted MR image shows a tumor that involves the posterior fossa (arrow). (b) Axial contrast-enhanced T1-weighted MR image obtained after surgery (cranio-orbitozygomatic approach) shows complete resection of the tumor (arrows).
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Figure 22a. (a) Preoperative sagittal T1-weighted MR image demonstrates a tumor with clival and intradural extension (arrows). (b) Sagittal T1-weighted MR image obtained after surgery performed through the midline (transmaxillary approach) reveals complete resection of the tumor (arrow).
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Figure 22b. (a) Preoperative sagittal T1-weighted MR image demonstrates a tumor with clival and intradural extension (arrows). (b) Sagittal T1-weighted MR image obtained after surgery performed through the midline (transmaxillary approach) reveals complete resection of the tumor (arrow).
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Residual tumors can be successfully treated with radiation therapy (7,31,32). Pre- and postoperative CT and MR imaging findings and surgical findings form the basis for accurate treatment and delivery of radiation. The use of fractionated proton beam radiation therapy permits delivery of tumor doses 15%–35% higher than those associated with standard x-ray therapy, allowing improved local control and higher survival rates (31). The recurrence-free 5-year survival rate for patients with skull base chordoma who undergo combined treatment with surgery and radiation therapy is 60%–70%. Surgery plus radiation therapy remains the most effective treatment (32,33).
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Recurrence and Metastasis
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Local recurrence of intracranial chordomas is still common regardless of the mode of therapy (31). MR imaging is the modality of choice for postsurgical follow-up and detection of recurrence. Parenchymal signal intensity changes are frequently observed at MR imaging performed after surgery or radiation therapy, especially in the temporal lobe and visual pathways. Local recurrence is more common following subtotal or partial tumor resection. Striking hyperintensity at T2-weighted MR imaging is helpful in suggesting tumor recurrence rather than postoperative changes. Contrast-enhanced images are also valuable in making this distinction and in delineating recurrent tumor margins. Tumor recurrence can occur along the surgical pathway but is uncommon; it was described in only 5% of cases in one large series (Fig 23) (34). Distant metastasis is rare (Fig 24), although in one study it was observed in 7%–14% of intracranial chordomas as pulmonary, liver, bone, or lymph node involvement (1).
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Figure 23a. (a) Presurgical axial CT scan shows a mass primarily in the sellar area (arrow). A transmaxillary surgical approach was used to resect the tumor. (b) Axial contrast-enhanced T1-weighted MR image obtained 1 year after surgery shows recurrent tumor at the surgical site in the nasal region (arrows). (c) Postsurgical sagittal CT scan shows recurrent tumor in the clival area (arrow).
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Figure 23b. (a) Presurgical axial CT scan shows a mass primarily in the sellar area (arrow). A transmaxillary surgical approach was used to resect the tumor. (b) Axial contrast-enhanced T1-weighted MR image obtained 1 year after surgery shows recurrent tumor at the surgical site in the nasal region (arrows). (c) Postsurgical sagittal CT scan shows recurrent tumor in the clival area (arrow).
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Figure 23c. (a) Presurgical axial CT scan shows a mass primarily in the sellar area (arrow). A transmaxillary surgical approach was used to resect the tumor. (b) Axial contrast-enhanced T1-weighted MR image obtained 1 year after surgery shows recurrent tumor at the surgical site in the nasal region (arrows). (c) Postsurgical sagittal CT scan shows recurrent tumor in the clival area (arrow).
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Figure 24a. (a) Postsurgical axial CT scan shows a soft-tissue mass in the left infratemporal fossa (arrow). (b) Axial CT scan of the thoracic spine shows a destructive metastatic lesion in the left pedicle with adjacent soft-tissue extension (arrows). This finding represents distant metastatic spread of chordoma.
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Figure 24b. (a) Postsurgical axial CT scan shows a soft-tissue mass in the left infratemporal fossa (arrow). (b) Axial CT scan of the thoracic spine shows a destructive metastatic lesion in the left pedicle with adjacent soft-tissue extension (arrows). This finding represents distant metastatic spread of chordoma.
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Differential Diagnosis
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Chondrosarcomas are the lesions most often confused with intracranial chordomas (35). Unlike intracranial chordomas, which have a midline skull base location, the majority of chondrosarcomas arise along the petro-occipital fissure. However, chondrosarcomas can sometimes have a midline location, making differentiation between a chondrosarcoma and an intracranial chordoma difficult. Also, the two tumors have similar signal intensity on T1- and T2-weighted MR images. Therefore, linear, globular, or arclike calcifications when present in chondrosarcomas can help distinguish them from intracranial chordomas (19).
Clival meningiomas have a dural attachment and do not have the appearance of a destructive bone lesion. Instead, they cause bone sclerosis and demonstrate homogeneous enhancement (27). They also have a characteristic angiographic appearance.
Nasopharyngeal malignancies usually extend more anteriorly and have associated head and neck lymphadenopathy. Plasmocytoma and lymphoma occasionally involve the skull base and cause lytic bone destruction. If centrally located, these tumors can mimic intracranial chordomas. Craniopharyngiomas, besides demonstrating a relatively characteristic signal intensity, are located more anteriorly and superiorly in midline than are intracranial chordomas. Because skull base metastases are relatively infrequent in the absence of a primary neoplasm, they should be viewed as an unlikely differential diagnosis. Additionally, the extraosseous tumor component of metastases is usually small relative to the intracranial chordoma.
Rhabdomyosarcoma should be considered in pediatric patients. This malignancy usually originates from the nasopharynx and manifests as a large, bulky intra- and extracranial tumor with associated lytic bone destruction (19).
Other differential diagnoses, although rare, include aggressive pituitary adenoma, histiocytosis X, dermoid and epidermoid cysts, trigeminal neuroma, and fibrous dysplasia (27).
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Summary
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Intracranial chordomas are rare midline tumors of clival origin. MR imaging and CT are the imaging modalities of choice for diagnosis, treatment, and follow-up. Intracranial chordomas are often visualized as soft-tissue masses that originate from the clivus with extensive lytic bone destruction. They commonly displace or partially encase intracranial arteries, but arterial narrowing is rare. Classic findings in intracranial chordomas include intermediate to low signal intensity on T1-weighted MR images and very high signal intensity on T2-weighted images. Enhance
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Abstract
LEARNING OBJECTIVES FOR TEST...
