79Chordomas are rare primary bone tumor
thought to arise from transformed notochord
remnants with an estimated incidence rate of
0.08–0.09 per 100,000. It occurs most commonly
in males with a peak incidence in their fourth to
fifth decades of life and rarely affects children
and adolescents. Skull base chordomas are essen-
tially midline lesions that occur at the vicinity of
the clivus (spheno-occipital bones) and represent
only 0.15% of all intracranial tumors [ 8 ]. They
are considered a low-malignancy neoplasm with
slow-growing pattern that rarely metastasizes.
However, chordomas have a local aggressive
behavior and high recurrence rates [ 11 – 13 ].
The slow-growing nature of most skull base
chordomas and chondrosarcomas often leads to
variable presentation of clinical signs and symp-
toms based on the location of the tumor.
Treatment goals should involve complete surgi-
cal resection that should be tempered with a judi-
cious effort to avoid neurological compromise.
The extent of surgical resection correlates directly
with recurrence rates. Among all chordoma
patients, median survival is 6.29 years with 5-,
10-, and 20-year survival rates precipitously
dropping to 67.6%, 39.9%, and 13.1% across all
races and genders underscoring the dismal prog-
nosis of this disease. Nonsurgical management or
observation may be reserved for some patients
who are high-risk surgical candidates.
Chondrosarcomas tend to have a slightly better
prognosis and are regarded to be less aggressive
with higher recurrence-free survival rates when
compared to chordoma. In one study, recurrence-
free survival at 5 years was as high as 90%.
Surgical and postoperative management goals of
chordomas and chondrosarcomas are often very
similar, and case series often report results for
both these pathologies together because of the
rarity of the diseases.
While aggressive gross total resection may be
achieved through a variety of skull base
approaches including EEA (Fig. 6.4), en bloc
resection may not be feasible in the skull base as
has been described in the spine due to involve-
ment of critical neurovascular structures, with
surgeons most often resorting to piecemeal
removal of the tumor. Based on available clinical
case series from experienced skull base surgeons,
aggressive surgical resection is only possible
48–61% of the time underscoring the technical
challenge that surgeons have with treatment of
tumors in this location. As a result, radiation
treatment has played an important role in the
postoperative management of these patients.Preoperative Radiological Assessment
Radiologic investigation and preoperative plan-
ning for skull base approaches of chordomas and
chondrosarcomas have greatly improved because
of rapidly evolving imaging methods. Computed
tomography (CT) and magnetic resonance imag-
ing (MRI) should always be performed in cases
of suspected skull base bone lesion for bone and
soft tissue assessment, respectively. The combi-
nation of these two radiologic modalities permits
the definition of important diagnostic and thera-
peutic characteristics of skull base tumors: radio-
logic appearance, location, extension, and
relation to critical neurovascular structures.
Chordomas and chondrosarcomas have an
overall similar appearance on MRI, and some-
times it is impossible to differentiate them with-
out histopathology. In general, chordomas
typically present as midline extradural masses
originating within bone and tend to expand poste-
riorly and laterally. They usually present as well-
delineated soft tissue masses that may displace
and compress adjacent structures. More advanced
tumors show local invasiveness and characteristic
bone destruction.
The CT scans demonstrate best bone erosion,
osteolysis, and intratumoral calcifications.
There is typically no surrounding sclerosis.
Moderate to marked heterogeneous enhance-
ment following administration of iodinated con-
trast material can also be depicted. Most
chordomas are hypointense or isointense on
T1-weighted images. High signal correlates
with hemorrhage or mucinous collection.
T2-weighted images characteristically demon-
strate a high signal. Gadolinium enhancement is
mostly heterogeneous and often presents a
“honeycomb” appearance [ 14 ].
Chondroid chordomas represent 5–15% of all
chordomas and are characterized by the partial6 Endoscopic Endonasal Approach for Posterior Fossa Tumors