Intracranial chordomas are rare, slow-growing tumors that arise from remnants of the embryonic notochord in the skull base. They typically present as soft tissue masses originating in the clivus with associated bone destruction. MR imaging and CT are effective in diagnosing and monitoring these tumors. Treatment involves surgical resection followed by radiation therapy, which provides the best outcomes for patients with intracranial chordomas.

1. INTRACRANIAL CHORDOMA
Duc Tuan Tran Vo

2. Overview
• Chordomas are relatively rare (0.51 cs/106) 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 lie in bone
(extradural)
• Chordomas are considered to be low-grade neoplasms, locally
invasive, but they rarely metastasize
• Chordomas account for 1% of intracranial tumors and 4% of all
primary bone tumors

3. Epidemics
• Chordomas were relatively evenly distributed along the cranial (32%),
spinal (32.8%), and sacral (29.2%) portions of the axial skeleton
• 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.
• Intracranial chordomas constitute one-third of all chordomas and
usually occur in the vicinity of the clivus (spheno-occipital bones),
may arise unilaterally from the petrous apex.

4. Three-dimensional CT scan demonstrates the sites of origin of
intracranial chordomas: the upper (yellow), middle (red), and lower
(green) clivus

5. Sagittal T1-weighted MR images
demonstrate involvement of the
upper, middle, and lower clivus.

6. Clinical features
• 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

7. Characteristics
• 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.
• 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.

8. • Thin-section axial and coronal unenhanced and contrast material–
enhanced images are usually obtained for assessment.
• The classic appearance of intracranial chordoma at high-resolution CT
is that of a centrally located, well-circumscribed, expansive 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.

9. • Sagittal reformatted CT scan reveals bone sequestra at the distal
end of a lytic clival lesion (arrows).

10. • Axial CT scan of the skull base
demonstrates the lesion with a clival
origin and extension to the
prepontine cistern with typical
trabecular entrapment

11. • 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.

12. MR Imaging
• MR imaging is the single best modality for radiologic evaluation of
intracranial chordomas.
• MR is considerably superior to CT in the delineation of lesion extent
because it provides excellent tissue contrast and exquisite anatomic detail
• 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

13. • MR imaging is deficient only in the evaluation of calcification and
cortical bone. Osseous destruction is implied by replacement of the
signal void of cortical bone with the soft-tissue signal intensity of
tumor.
• Use of contrast-enhanced imaging can solve this problem

14. T1W
• 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.
• 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. The presence of hemorrhagic foci can
be confirmed with gradient-echo imaging that is susceptible to blood.

15. (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)

16. 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.

17. T2W
• Classic intracranial chordoma has high signal intensity on T2-weighted
images, 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.
• Low-signal-intensity septations that separate high-signal-intensity
lobules are commonly seen corresponding to the multilobulated gross
morphologic features of the tumor.
• Also, T2-weighted imaging is excellent for differentiating tumor from
adjacent neural structures

18. • The majority of intracranial chordomas demonstrate moderate to
marked enhancement following contrast material injection.
Occasionally, the enhancement is slight or even absent. 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.
• 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.

19. • Sze et al 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

21. 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. Despite the high frequency of intracranial arterial
involvement, arterial narrowing is rare in intracranial chordomas, 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. Venous involvement or occlusion is also readily visualized at
MR venography.

22. • Angiographic evaluation of intracranial chordomas is nonspecific.
Abnormal tumor vascularity or staining is rare. 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.

23. Tumor Spread
• The classic midline clival chordoma can spread anteriorly, laterally, posteriorly, inferiorly, and
superiorly, 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.

24. Treatment
• Surgical removal is a very effective treatment for intracranial
chordomas. Longer survival rates have been associated with more
extensive tumor removal
• Residual tumors can be successfully treated with radiation therapy
• 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

25. Recurrence and Metastasis
• Local recurrence of intracranial chordomas is still common regardless of
the mode of therapy
• 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. Striking
hyperintensity at T2-weighted MR imaging is helpful in suggesting tumor
recurrence rather than postoperative changes. Local recurrence is more
common following subtotal or partial tumor resection.
• Tumor recurrence can occur along the surgical pathway but is uncommon;
it was described in only 5% of cases in one large series. Distant metastasis
is rare, although in one study it was observed in 7%–14% of intracranial
chordomas as pulmonary, liver, bone, or lymph node involvement.

26. Differential Diagnosis
• Chondrosarcomas are the lesions most often confused with
intracranial chordomas. 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 chordoma.

27. • 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. They also
have a characteristic angiographic appearance.

28. • 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.

29. • Other differential diagnoses, although rare, include aggressive
pituitary adenoma, histiocytosis X, dermoid and epidermoid cysts,
trigeminal neuroma, and fibrous dysplasia

30. Summary
• 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. Enhancement is marked and often heterogeneous.
• Treatment that consists of radical surgical resection followed by proton
beam radiation therapy achieves the best results.