Abstract
Chordomas and chondrosarcomas are different histopathological entities with markedly different natural history and clinical outcomes. Sharing a similar clinical and radiological presentation, their definite identification is confirmed only by immunohistological stain (cytokeratin, EMA, and brachyury). One common prognostic feature is the radicality achieved with surgical resection. Due to their large or giant size at presentation or their extension to multiple anatomical compartments, radical resection of these tumors often requires more than one approach or one surgical procedure, and staged surgery becomes necessary. The pursuit of gross total removal improves the disease-free survival in chordoma, knowing that a high-dose radiation therapy will be given in addition, whereas in chondrosarcoma, achieving total removal would eliminate the need for radiation. Multiple and staged surgery requires thorough planning that takes into consideration the recovery time, reconstruction, donor site of autologous tissue, and the potential complications of the approach, particularly of cerebrospinal fluid leak. As a rule, the surgical treatment of chordomas and chondrosarcomas should aim to achieve total and radical removal. This will require mastering and utilizing various skull base approaches and employing all the technical advancements available in our armamentarium and the availability of intraoperative imaging and navigation.
Keywords
Chondrosarcoma, Chordoma, Clivus, Skull base tumors, Surgical approaches, Tumor excision
Outline
Introduction 231
Preoperative Planning 234
Surgical Strategies 235
Anterior Approaches for Midline Tumors 235
Endoscopic-Assisted Techniques 236
Transsphenoidal and Extended Transsphenoidal Approach 236
Transmaxillary Approach 237
Lateral Approaches for Paramedian Tumors 237
Staged Approaches for Tumors With Extracranial Extension 238
Illustrative Cases 238
Conclusions 238
References 239
© 2018 Elsevier Inc. All rights reserved. Please note that the copyright for the original figures submitted by the contributors is owned by Contributors.
Introduction
Chordomas and chondrosarcomas are rare skull base tumors, with an incidence of less than 0.03 per 100,000 persons. Although they have similar sites of origin, histologies (definitely distinguished only by immunohistochemical stain ), clinical presentations, and radiological features, they differ in natural history and clinical outcome. Surgical resection, with the aim of radical tumor removal, is recommended for most patients with skull base chordomas and chondrosarcomas. Although both tumors arise in the bone and infiltrate paths of least bony resistance until rupturing through the cortex and forming a mass in the soft tissue, chordomas originate in the midline and grow laterally in both directions, whereas chondrosarcomas arise laterally, from the petroclival syncohondrosis, and grow predominantly ipsilaterally. Because of this difference, surgical strategies differ. Chordomas commonly require multiple surgical exposures for radical resection [as depicted in illustrative cases 1 and 2 ( Figs. 20.3 and 20.4 )], as they frequently involve multiple anatomical areas inaccessible via only one approach. In contrast, chondrosarcomas, despite their frequent large size at the presentation, can be usually be removed by one operation ( Figs. 20.1 and 20.2 ). The surgeon who treats both types of tumor must master multiple skull base approaches. Also, each approach must be tailored to maximize exposure and facilitate dissection of tumor wherever it extends. The following anatomical classification based on the pattern of extension aids in the selection of surgical approach :
Type I: small, isolated (symptomatic or asymptomatic)—radical removal with bone margin in one surgical approach.
Type II: relatively large size in continuous areas—radical removal with only one surgical approach.
Type III: extending through the skull base—two or more skull base approaches to achieve radical removal.
Dural invasion is another important consideration in the choice of operative approach. Direct dural invasion is a common pattern of extension, particularly of chordomas, and cavernous sinus invasion frequently arises from spread of the tumor along the sixth cranial nerve. All approaches first encounter the extradural tumor; any transdural extension is followed through the resulting dural defect to the intradural tumor. Primarily intradural cranial approaches should be avoided as the chordoma can be spread by the dispersion of cells in the cerebrospinal fluid (CSF). Tumor can also be seeded along the operative route and at donor sites for reconstruction ( Fig. 20.6 ). To minimize the former, before the tumor capsule is disrupted, the operative corridor wall is lined with cottonoids or other barrier material, contact of instrument with normal tissue is avoided, and the tips of the instruments are not touched by the surgical team. To avoid the last of these three, the fat or fascial graft is harvested from a totally separate, sterile field with clean instruments and a newly dressed surgical team. The instruments used in the main operation are considered to be tumor contaminated, as are the surgical drapes, towels, and gloves.
For almost all chordomas requiring multiple approaches, the anterior approach is performed first. Lateral extension often requires one or more lateral approaches, and inferolateral extension to the condyle may require a stabilizing occipitocervical fusion, which is often deferred to the final stage.
Recurrent cases present quite a challenge, particularly in reconstruction, in preventing CSF leakage (see Chapter 37 ). The challenge and risk increase markedly following radiation therapy, which promotes angiopathy that increases the risk of vascular injury. Extensive scarring from previous surgery and radiation may warrant the choice of an alternative approach. In this chapter, surgical strategies that include two or more approaches to achieve safe radical tumor removal will be discussed.
Preoperative Planning
The anatomical localization and extension of these lesions warrant comprehensive clinical, ophthalmological, and endocrinological evaluations. Any symptoms, signs, or radiographic concern for lower cranial nerve dysfunction or involvement (cranial nerves IX, X, XI, and XII), such as swallowing difficulty or voice change, warrant formal assessment. Neuroimaging studies must include thin cuts of multiplanar magnetic resonance (MR) sequences with and without contrast and thin high-resolution computed tomographic (CT) scans with multiplanar axial, coronal, and sagittal reconstruction. Bone window CT is essential to understanding the destruction of surrounding bony structures and extension into the suprasellar, parasellar, and cavernous sinus regions, as well as the anterior, middle, and posterior fossae; the infratemporal fossa; petrous apex; foramen magnum; occipital condyle; air sinuses; and parapharyngeal spaces. Vascular imaging including both arterial and venous phases is obtained in all cases; vascular supply to the tumor and large vessel encasement or displacement should be noted in planning the surgical approach. Dynamic CT simultaneously depicts bony structure and cerebral vasculature. Cerebral angiograms an balloon test occlusion are rarely necessary, except in cases with high risk of carotid injury, such as a recurrent tumor extending into the cavernous sinus in a previously irradiated field ( Fig. 20.5 ).
Stereotactic navigation, fixed or floating head, is used for intraoperative localization and to assess the extent of resection; segmentation aids depiction of the neurovascular structures displaced or encased by the tumor ( Fig. 20.7 ). The endoscope is routinely used, sometimes simultaneously and frequently alternating with the operating microscope, to visualize and remove tumor outside the view of the microscope ( Fig. 20.8 ). Intraoperative Doppler microultrasonography helps identify arteries and verify their permeability after manipulation. Intraoperative imaging with CT or MR may also be valuable ( Fig. 20.9 ). If they are not available, then immediate postoperative imaging should be performed to determine the extent of removal and the need for additional surgery.
Intraoperative neurophysiological monitoring of electroencephalographic patterns, somatosensory evoked potentials, auditory brainstem evoked potentials, and electromyography of cranial nerves III, IV, V, VI, VII, X, XI, and XII, as required by tumor extension, is essential and improves the surgical results. Anticipation of manipulation of the pituitary gland, which is often required, warrants administration of 100 mg of hydrocortisone at the beginning of surgery and subsequent tapering to any maintenance dose required postoperatively.
Surgical Strategies
Harvey Cushing, in 1909 via a transsphenoidal route, was the first surgeon to successfully resect a chordoma; reoperation was performed a few months later for additional resection. The diagnosis of chordoma was made retrospectively by Bailey and Bagdasar in 1929. Subsequently, the routes for chordoma removal have expanded to include almost all skull base approaches (see Chapter 10 ). These can be grouped into two main categories: anterior and lateral. A combination of anterior and lateral approaches is recommended for type III tumors.
Anterior Approaches for Midline Tumors
The anterior approaches provide the most direct trajectory to the clivus, thus allowing the surgeon to reach the tumor in a short time, with minimal bony and soft tissue dissection and limited manipulation or dissection of neural structures. Anterior approaches work along the most common direction (anterioposterior) of tumor growth and permit tumor removal with limited displacement and disruption of surrounding structures. Anterior approaches may be used in combination to expose clival lesions and include the following: transoral, transsphenoidal, transmaxillary, transfacial, and transbasal. Endoscopic techniques have fostered the trend toward less facial dissection.
Endoscopic-Assisted Techniques
Endoscopic surgery has flourished recently with applications beyond pituitary tumors as both the sole and a complementary visualization tool. The endoscope allows visualization of anatomy that would not be seen by the microscope without additional disruptive dissection. Its maneuverability, proximity to the field, and angled lenses can provide close-up, panoramic, although two-dimensional, views that include anatomy deep to structures that obscure the direct line of sight of the microscope. This better visualization can facilitate safer, more complete tumor resection. For instance, in removing the intradural component of a clival chordoma, 30 and/or 70 degree angled endoscopes permit visualization and removal of tumor peripheral to the dural opening.
Transsphenoidal and Extended Transsphenoidal Approach
The classic transsphenoidal approach is useful for some clival chordomas limited to the upper clivus, including those invading the medial wall of the cavernous sinus. This approach does not allow radical removal of a more extensive mass, for which a wider exposure can be achieved with the transsphenooethmoidal approach. For tumors limited to the upper clivus, sella, or the medial cavernous sinus, we use a variant of this approach, called the extended transsphenoidal approach. For tumors extending lower in the clivus and with more lateral extension with or without involving the cavernous sinus, an additional osteotomy of the frontal process of the maxilla contralateral to the lesion is incorporated into the surgical approach to allow a more lateral, wider exposure of the area. Anteriorly, the limit of the exposure is still the cribriform plate. If necessary, part of the superior aspect of the hard palate can be shaved to gain visibility of the more inferior clivus. After the anterior wall of the sphenoid is widely exposed and the anterior aspect of the clivus is dissected to gain maximal caudal exposure, if necessary to expose the dorsum sella and posterior clinoid, the pituitary fossa is removed and the sella dura and the gland are carefully displaced upward. This provides full exposure of the clivus from the dorsum sella to the foramen magnum. The clivus can be drilled away, and a wide corridor of access extending from the planum sphenoidale to the anterior lip of foramen magnum can be safely achieved. However, significant restrictions remain laterally. In the upper clivus, these include the optic canals, the cavernous and petrous segments of the internal carotid arteries, and the petrous apex. In the midclivus, the surgical window widens but is still restricted between the points of entry of the sixth nerves into the Dorello canal. In the lower clivus, lateral limits are the hypoglossal canals and the twelve cranial nerves.
The endoscope, with lenses angled at 0, 30, 45, and 70 degree, helps expand the view through this narrow corridor during all stages of the procedure—opening of the surgical aperture, tumor removal, securing hemostasis and creating a watertight closure. In one series, the endoscopic view was found valuable in almost 50% of the cases. In closing this approach, the dural opening is closed with an inlay of fascia lata, wider than the defect and secured to the dural edges with small staples. The fascia graft is reinforced on the outside by fat and sealed with fibrin glue. Fat also fills the bone defect. The maxillotomy is repaired with low-profile microplating.
Adding uni- or bilateral anterior wall maxillotomies to the traditional sublabial transsphenoidal approach achieve wider exposure for the introduction and manipulation of instruments such as a drill and ultrasonic aspirator, without visual obstruction. Nasal and pharyngeal mucosa are displaced but preserved and returned to the normal position in closure. This provides vascularized tissue to the packed clivus and obviates reconstruction with a septal flap. This wide corridor can be coated to limit dissection and prevent tumor seeding without causing obstruction. It facilitates optimal and even simultaneous use of both the microscope and endoscope and thus realization of the full advantages of both.
Transmaxillary Approach
The transmaxillary approach is indicated for midline clival lesions extending into the nasopharynx or craniocervical junction, inferior to the anterior cranial fossa, superior to the C2-C3 interspace, and medial to the pterygoid plate. It is also appropriate for lesions that extend to the internal carotid artery at the level of the foramen lacerum, the cavernous sinus, the hypoglossal canal, and the jugular foramen. It has several variations: (1) the Le Fort I osteotomy, with or without midline splitting of the hard and soft palates and (2) the unilateral maxillotomy, with paramedian splitting of the hard and soft palates. The unilateral paramedian maxillotomy with preservation of the soft palate provides an excellent collateral blood supply to the swing maxilla and maintains the contralateral maxillary bone intact, such that its vascularization and skeletal fixation are unaffected. The limitations of the transmaxillary approach are (1) rostrocaudally, the base of the anterior cranial fossa and the C2-C3 interspace and (2) laterally, the medial pterygoid plate, the internal carotid artery (ICA) at the level of the foramen lacerum and cavernous sinus, the hypoglossal canal, and the jugular foramen. Tumors that invade the cavernous sinus can be removed when the tumor is medial to the intracavernous ICA. Lateral extensions in the cavernous sinus are safely removed by a transcranial approach. The potential complications of the transmaxillary approach are directly related to the surgical variant used. The risk of aseptic bone necrosis is increased with multisegment osteotomies and intraoperative hypotension. Major hemorrhage and accidental fractures of the pterygoid plate using the osteotome are uncommon complications of this approach.
Lateral Approaches for Paramedian Tumors
Lateral approaches are necessary for the safe resection of type III chordomas and chondrosarcomas with significant lateral extension. These include expansions of the traditional frontotemporal, subtemporal, and suboccipital craniotomies, such as the cranioorbital zygomatic (COZ), the extended middle fossa, and the transcondylar approaches, respectively. These approaches employ extensive bone removal to increase the working space and to reduce the depth of the surgical corridor so as to allow more precise microdissection from multiple operative angles.
Cranioorbital Zygomatic Approach (see Chapter 14 )
Removal of the orbital rim and detachment of the zygomatic arch in combination with a frontotemporal craniotomy gives wide surgical access to extradural tumors extending into the orbit, sellar, and parasellar regions and the anterior and middle cranial fossae. It also exposes tumors of the infratemporal and pterygopalatine fossae. Detachment of the zygomatic arch also provides better views of intradural lesions of the interpeduncular fossa.
The COZ is a versatile approach that provides access to chordomas and chondrosarcomas originating in the upper clival area and extending laterally to the middle cranial fossa, petrous apex, and infratemporal fossa. It is particularly useful in tumors that extend intradurally, as do up to 48% of chordomas.
Several advantages of the COZ approach have been described: (1) it provides increased surgical access to the inferior surfaces of frontal and temporal lobes thus minimizing the necessity of brain retraction; (2) it shortens the distance between the cranial surface and the targeted lesion at the skull base; (3) it provides skull base surgical access via multiple operative angles (subfrontal, transsylvian, and subtemporal); (4) it provides vascularized tissue, pericranium, and temporalis muscle and/or fascia to repair skull defects along the floors of the anterior and middle cranial fossae; and (5) it potentially minimizes intraoperative blood loss by enabling early tumor devascularization along the sphenoid ridge. Furthermore, the COZ provides (1) visualization of the ICA from its cavernous segment to its bifurcation; (2) visualization of the upper basilar artery, its bifurcation, and the posterior communicating and posterior cerebral arteries; (3) visualization of the optic apparatus; (4) access to the tentorial notch; (5) visualization of cranial nerves I through VIII; and (7) access to the petrous apex.
Extended Middle Fossa Approach (see Chapter 15 )
The middle fossa approach creates an extradural surgical corridor that potentially extends from the petrous apex to the jugular foramen via a subtemporal craniotomy. Removal of the petrous apex provides access to the anterolateral cerebellum-pontine angle. The extended middle fossa approach also provides access to lesions located in the pterygopalatine, temporal, and infratemporal fossae; orbit; cavernous sinus; and pharyngeal region. The sphenoid sinus may also be exposed via the anteromedial or anterolateral middle fossa triangles. Sectioning of the mandibular division of the trigeminal nerve provides access to the lower clivus. Additional dissection of the temporal bone and infratemporal fossa increases exposure and allows skull base reconstruction with vascularized tissue.
Transcondylar Approach (see Chapter 19 )
Lateral extension of the suboccipital approach below the jugular foramen in a far lateral approach provides access to the anterior aspect of the craniovertebral junction including the lower clivus. The occipital condyle can be partially or completely removed; variants have been termed retrocondylar, supracondylar, paracondylar, or transcondylar approaches.
Chordomas and chondrosarcomas extending into the lower clival region present significant challenge to complete resection. In fact, a combination of approaches, usually endoscopic endonasal and lateral, was required for most tumors involving the craniocervical junction according to two studies of a total of 95 patients with skull base chordomas and chondrosarcomas. The multiple variations of the far-lateral approach may be also combined with other open transcranial approaches, such as transtemporal and infratemporal approaches, to increase surgical access to multiple regions of the skull base.
The far-lateral approach is the best option for extradural tumors in the inferior clivus with lateral extradural or medial intradural extension to the craniocervical junction or upper cervical area. It opens views of the region ventral to the medulla and cervical spinal cord, with minimal neural manipulation and good control of the ipsilateral vertebral artery, and its angle of approach facilities safe dissection of the tumor from the brainstem, cranial nerves, and blood vessels through a relatively wide and short surgical field. Limitations include the jugular bulb superiorly and the condyle anteriorly. Excessive drilling of the condyle destabilizes the occiput–C1 articulation, necessitating occipitocervical stabilization (see Chapter 23 ).
Staged Approaches for Tumors With Extracranial Extension
Staged approaches may be also recommended for skull base tumors extending extracranially. In a recent series of 35 skull base chondrosarcomas, tumors extending into the parapharyngeal space and upper cervical spine region were more likely to require a staged operation for tumor resection. Transoral and transcervical approaches may be required in these situations.
Illustrative Cases
Case 1
A 30-year-old man with a skull base chordoma presented with 1 year of diplopia and increasing facial numbness. The tumor involved the clivus, left infratemporal fossa, and both cavernous sinuses ( Fig. 20.3A–D ). Three procedures were performed: an initial transsphenoidal approach for resection of the midline component of the tumor, followed by a left transzygomatic approach for infratemporal and left cavernous sinus tumor removal ( Fig. 20.3E ), and then a similar contralateral approach resection of right cavernous sinus tumor ( Fig. 20.3F ). The patient recovered completely and underwent adjuvant postoperative proton beam radiation. Seven years later, the tumor recurred as a sarcoma.
Case 2
A 12-year-old boy presented with headaches, left-sided weakness, and gait ataxia. Radiological evaluation showed a large clival chordoma extending into the occipital condyles and severely compressing the brainstem ( Fig. 20.4A–D ). The midline component of the tumor was removed by a first-stage anterior sublabial transmaxillary approach. Then a second-stage transcondylar approach removed the tumor remaining at the craniocervical junction ( Fig. 20.4D–F ). Extensive condylar involvement warranted occipitocervical fusion, performed the following day. The patient recovered completely and remains disease free after 18 years of follow-up.
Related posts:
Pathology of Chordoma and Chondrosarcoma of the Axial Skeleton
Midline Subfrontal Approaches: The Transbasal Approach and Extended Modifications to Access the Clivus
Chordomas and Chondrosarcomas of the Skull Base: Transpetrosal Approaches
Surgical Management of Chordomas and Chondrosarcomas of the Cervical Spine
Stereotactic Radiosurgery for Skull Base Chordomas and Chondrosarcomas
Recurrent Skull Base Chordomas: Role of Surgery
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