18.1 Introduction

This chapter focuses on the surgical treatment of clival tumors. Because clival chordoma is the archetypal tumor in this location, specific comments regarding this tumor type will be made. Irrespective of the pathology, the bone of the clivus may be infiltrated by tumor and require resection beyond the grossly visible tumor margin. The majority of tumors in this location are large at diagnosis and extend to the anterior cranial fossa or parasellar region; ventrally into the nasal cavity, paranasal sinuses, or nasopharynx; or to the middle fossa.

18.2 Surgical Anatomy

The clivus is formed from the part of the basilar occipital bone that extends anteriorly and superiorly from the foramen magnum and from the body of the sphenoid bone. These two bones articulate at the spheno-occipital synchondrosis. The clivus thus extends from the dorsum sella and the posterior clinoid processes to the foramen magnum. At its superior aspect the clivus is bordered laterally by the petroclival fissure synchondrosis) and the petrous temporal bone. The petroclival fissure terminates in the jugular foramen posterolaterally. The pharyngeal tubercle located on the anterior and inferior surface of the clivus is the site of attachment of the pharyngeal raphe and the anterior longitudinal ligament. Laterally, the supracondylar groove marks the location of the underlying hypoglossal canal. A rich venous plexus exists between the periosteal and meningeal layers of the clival dura. The inferior petrosal sinus runs along the petroclival fissure and connects the clival venous plexus and the posterior cavernous sinus to the jugular bulb. The abducens nerve penetrates the inferior petrosal sinus at Dorello’s canal, at the lateral limits of the midclivus, and courses superiorly medial to the petrous apex to enter the posterior cavernous sinus. The foramen lacerum and the internal carotid artery are at the level of the floor of the sphenoid sinus and are identified surgically by following the vidian canal superiorly and laterally. Mobilization of the Eustachian tube allows access to the inferoventral clivus and petroclival fissure to the jugular foramen. The medulla, pons, and midbrain and the vertebrobasilar arterial tree lie directly behind the clivus. The posterolateral aspects of the basiocciput form the occipital condyles and transmit the hypoglossal nerves.1 ^,​ 12 ^,​ 13 ^,​ 18

18.3 Diagnostic Imaging, Regional Pathology, and Differential Diagnosis

High-resolution CT scanning allows the accurate assessment of bony destruction by the tumor, which is universally present in chordomas (Fig. 18.1).40 Integrity of the optic and carotid canals can be best assessed in this way. Tumoral calcification is well seen if present. If there is a question of occipitocervical instability, plain X-ray films of the cervical spine, both in flexion and extension, are performed.

Multiplanar MRI with and without contrast enhancement best demonstrates the extent of the tumor and best identifies important adjacent neurovascular structures, such as brainstem, optic nerves and chiasm, and internal carotid and basilar arteries. Fat-suppression techniques highlight tumoral contrast enhancement within or adjacent to fatty areas such as the orbits and bone marrow.39 ^,​ 40

CT angiography is very valuable in the assessment and surgical management of clival tumors. It accurately visualizes the relationships of the internal carotid artery (ICA) to the tumor and the tumor-infiltrated bone of the clivus. Along with preoperative volumetric MRI, it is typically coregistered and imported into intraoperative navigational devices so as to aid anatomic navigation of the central skull base.

Cerebral angiography is not typically necessary for the diagnosis of clival tumors; it is used when a detailed view of the head and neck and intracranial vasculature is desired. Important anatomic variations are noted, such as the pattern of venous drainage or the integrity of the circle of Willis. Vascular distortion and narrowing are well identified. Preoperative temporary balloon occlusion testing of the ICA may be performed if ICA occlusion or sacrifice is planned or if risk of arterial injury is deemed high. One or more complementary investigations of cerebrovascular reserve, such as transcranial Doppler, cerebral blood flow, or single-photon emission CT, may be used in conjunction with the temporary balloon occlusion test.

The differential diagnosis of an invasive clival mass includes chordoma, chondrosarcoma (although these tumors are usually found in a paramedian location), pituitary adenoma, metastasis, meningioma, nasopharyngeal carcinoma, plasmacytoma, and primary sphenoid sinus malignancy.

On conventional spin echo T1-weighted MRI, chordoma produces an intermediate to low signal intensity and is easily recognized amid the high signal intensity of the fat within the marrow of the clivus. Occasionally small foci of hyperintensity may be seen within the tumor on T1-weighted sequences. This finding may represent either intratumoral hemorrhage or mucin production by the tumor. T2-weighted MRI usually demonstrates high signal as a result of the high fluid content of the vacuolated cellular components. Areas within the tumor containing calcium, hemorrhage, or densely proteinaceous mucus will most often produce T2 hypointensity. Interlaced low-intensity septations separating high-signal intensity lobules are commonly visualized and correspond to the multilobular gross morphology of the tumor. Contrast enhancement is seen in the majority of chordomas and ranges from moderate to marked. The enhancement pattern of the tumor is often described as a “honeycomb” appearance that is created by intratumoral areas of low signal intensity (Fig. 18.2). Fat-suppressed images are useful for differentiating enhanced tumor margins from adjacent bright fatty bone marrow.39 ^,​ 40

As opposed to intracranial chordomas, which have a predilection for the midline of the skull base, the majority of chondrosarcomas are located more laterally along the petroclival fissure. Chondrosarcomas may, however, have a midline origin that makes preoperative differentiation from chordoma more challenging, as both have similar signal intensity on T1- and T2-weighted MR images (Fig. 18.3). Chondrosarcoma can sometimes be distinguished by the presence of linear, globular, or arclike matrix calcifications best identified on CT imaging.

Clival meningiomas represent another small subset of the pathologies encountered in this area. On MRI they appear as a well-circumscribed avidly and homogeneously contrast-enhancing mass with a dural attachment. They do not have the bony destruction associated with chordomas but may be associated with hyperostosis.

Nasopharyngeal cancers, including nasopharyngeal carcinoma, lymphoma and plasmacytomas, must always be considered in the differential for clival chordoma. They usually extend more anteriorly and may be associated with head and neck lymphadenopathy. These masses may produce lytic destruction of the skull base as well, which when centrally located may produce imaging that exactly mimics clival chordoma. Most of these tumors tend to be of low to intermediate signal intensity on T2-weighted imaging.

Pituitary macroadenomas may at times appear to involve and/or originate from the clivus. The inability to identify the pituitary gland in the presence of a large clival mass should raise the possibility of pituitary macroadenoma. A markedly elevated serum prolactin level may obviate the need for biopsy or resection.

Rhabdomyosarcoma represents another pathology that in children may develop in the clival region. This lesion takes origin in the nasopharynx and manifests as a large, bulky intra- and extracranial tumor with associated lytic osseous destruction of the skull base.

18.4 Clinical Assessment

All patients have a complete history and physical examination, including a neuro-ophthalmologic evaluation, which assesses visual acuity and fields, pupillary function, and ocular motility. Less than a third of these patients have a normal neuro-ophthalmological exam. Patients who have upper clival tumors undergo a complete endocrinologic assessment to identify evidence of pituitary or hypothalamic dysfunction. Patients who have mid- to lower clival tumors are assessed by an otolaryngologist with specific attention to hearing and lower cranial nerve (CN) function. An audiogram and direct laryngoscopy are usually performed.

The symptoms resulting from clival tumors depend on the specific sites of their extension (Table 18.1). The most common manifestation is a headache in the occipital or occipitocervical area, which may be aggravated by changes in neck position. Diplopia, the initial symptom experienced by most patients, is almost always the result of abducens neuropathy. Larger tumors may produce additional CN palsies manifesting as decreased visual acuity, facial weakness or numbness, hearing loss, dysphagia, and dysphonia. When tumors enlarge and produce brainstem or cerebellar compression, patients may develop ataxia, dysmetria, and motor weakness. When tumor extends into the retropharyngeal space or the nasal cavity, symptoms such as nasal obstruction, epistaxis, and throat fullness may develop.

18.5 Surgical Management

Numerous surgical approaches have been used to access the clivus. The choice of one approach over another should factor in the parameters of tumor location, size, and extension; unique patient anatomy and functional requirements; and the experience, expertise, and preferences of the surgical team. Small, midline upper clival tumors without lateral extension, for example, are probably best removed through an endoscopic transsphenoidal approach, whereas large tumors having lateral and intradural extensions may require both an endoscopic and an intracranial approach for adequate tumor removal. The advent of high-resolution cameras and the development of appropriate endoscopic microsurgical tools has supplanted the need for many of the open approaches traditionally used to access the central skull base. We no longer perform transfacial approaches and craniofacial translocations simply for tumor access but rather do so only when tumor resection requires the removal of tissues along these corridors. Table 18.2 lists the various surgical approaches traditionally used for clival tumor resection as well as the approaches currently used by our surgical team. The endonasal endoscopic approach to the clivus, and the transcondylar approaches, will be dealt with in detail.

18.6 Transsphenoidal (Microscopic) Approach

The transsphenoidal approach works well for smaller tumors located in the upper and middle clivus. Excellent exposure of the sphenoid sinus, sella turcica, and upper and middle clivus is possible.37 It has the disadvantages of limited inferior and lateral exposure, although the lateral exposure can be improved by entry into the medial maxillary sinus and removal of the pterygoid plate. The surgical field is typically deep and narrow, so there is little room available for aggressive bone resection.35 This approach has essentially been replaced by the endoscopic endonasal transsphenoidal approach, which offers greatly improved visualization, ease of expansion, and freedom of surgical movement.

18.7 Transsphenoethmoidal Approach

To expand the exposure offered by the microscopic transsphenoidal approach, an external ethmoidectomy with or without a medial maxillectomy was employed. Lalwani et al found this approach to be “adequate for the majority of tumors and disease processes present in the sphenoid sinus and clivus.”33 Addition of medial maxillectomy in instances of a narrow ethmoid sinus or inferiorly extending tumor allows improved access. Disadvantages include the necessity for facial incision and the limited exposure. The inferior limits can be extended by a medial maxillectomy as already described, but lateral reach is limited to approximately 2 cm from the midline.

18.8 Transoral–Transpalatal

After placement of an appropriate oral retractor system, the posterior pharyngeal wall and soft palate are divided to expose the clivus and upper cervical spine. Relatively limited exposure is obtained using this approach, which is most commonly employed for odontoidectomy.15 It is adequate for tumor biopsy or in the case of small lower clival tumors, but repair of intraoperative cerebrospinal fluid (CSF) leakage is problematic. Although fat and/or fascial tissue can be placed posterior to the pharyngeal wall, the pharyngeal wall rarely approximates well, and gaps are common, thus increasing the risk of CSF leakage. The transoral–transpalatal approach should not be the primary approach to intradural lesions at the foramen magnum unless other approaches prove ineffective.38

18.9 Transmaxillary Approaches

The transmaxillary approaches may prove useful for clival tumors that extend into the nasopharynx or craniocervical junction with minimal lateral extension. Numerous variations of this approach have been described. Most are based on a Le Fort I osteotomy with or without midline splitting of the hard and soft palates or a unilateral maxillotomy with median or paramedian splitting of the hard and soft palates.5 ^,​ 11 ^,​ 27 ^,​ 50 In the past, we preferred to avoid displacing or sectioning the palate and alveolar arch.13 ^,​ 14 ^,​ 41 ^,​ 42 Access to the maxilla was obtained via a facial degloving approach or through a lateral rhinotomy with lip split.13 ^,​ 49 Lateral exposure is limited by the pterygoid plates, the ICA at the level of the foramen lacerum and cavernous sinus, the hypoglossal canal, and the jugular foramen. Removal of the pterygoid plates allows access to the infratemporal fossa (ITF).17 ^,​ 43

Disadvantages of the transmaxillary approaches include the risk of ischemic osteonecrosis with multisegment osteotomies. This risk can be minimized by subtotally splitting the soft palate if palatal osteotomies are necessary and by leaving wide soft tissue attachments to freed maxillary compartments during swing procedures, or it can be avoided entirely by using transantral approaches. The principal disadvantage of the transmaxillary approach, however, is the inability to reliably stop CSF leakage. Direct repair of the dura is rarely possible and must rely on packing with fat, fascia, and fibrin glue without firm tissue available as a support to hold the repair in place. Elevation and use of vascularized mucosal flaps (septal, nasal, or turbinate) helps with healing and reduces CSF leak rate. Currently our only indication for this approach is the need to surgically resect the maxillary sinus in the presence of malignancy.

18.10 Transmandibular, Circumglossal, Retropharyngeal, Transpalatal Approach to Clivus and Upper Cervical Spine

Initially described by Biller et al and popularized by Krespi, and later by Ammirati, the transmandibular approach to the skull base provides simultaneous exposure of the middle and lateral compartments of the skull base, allows excellent vascular control and access to CNs IX to XII, and by straightforward expansion allows exposure that extends from the ipsilateral ITF to the contralateral medial pterygoid plate, from the anterior cranial fossa to the lower clivus and the anterior cervical spine down to C7 (Fig. 18.4).2 ^,​ 3 ^,​ 6 ^,​ 16 ^,​ 30 ^,​ 31 ^,​ 32 The main indications for this approach are large tumors involving both the middle and lateral compartments and tumors of the craniocervical junction and upper cervical spine, where wide resection of soft tissue and bone is required.

A good deal of anatomic dissection is required for this approach, which results in predictable morbidity. A temporary tracheostomy is required. Conductive hearing loss and serous otitis media result from section of the Eustachian tube. Temporary swallowing difficulties induced by the circumglossal and palatal incisions, the extensive retropharyngeal dissection, and the section of the tensor and levator pallatini muscles occasionally necessitate the insertion of a gastrostomy. Preoperative consultation with dentistry should be obtained to fashion a palatal stent with which to support the palatal mucosa after closure. This stent allows for improved apposition of the mucosa against the residual hard palate, helping prevent acute mucosal loss.

Because of this inherent morbidity, long and careful consideration should be given to the use of this approach, which should be reserved for instances in which surgical cure or significant palliation are likely.16 As noted, this approach is no longer used as a means of access to the clivus: the endoscopic approaches, at times in combination with posterolateral approaches, have obviated the need for this extensive operation (Fig. 18.5).

18.11 Extended Transbasal Approach

Developed by Tessier and Derome, the transbasal approach to the clivus was subsequently modified to incorporate orbital osteotomies in an effort to reduce frontal lobe retraction and to allow exposure of more posteriorly and laterally related structures such as the medial walls of the cavernous sinus and the hypoglossal canals.5 ^,​ 19 ^,​ 20 ^,​ 21 ^,​ 28 ^,​ 44 ^,​ 48 The approach consists of bifrontal craniotomy, bilateral orbital osteotomy (removal of supraorbital bar), ethmoidectomy, sphenoidectomy, and the extradural resection of the clivus. The limits of exposure are the foramen magnum inferiorly and the hypoglossal canals inferolaterally; the intracavernous carotid arteries form the superolateral limits. The posterior clinoids, dorsum sella, and the region behind and above the pituitary gland are obscured by the gland, making this a blind area when using the extended transbasal approach. The endoscopic approaches to the clivus have eliminated the use of this approach by offering improved visualization and access to the entire clivus without the need to manipulate the frontal lobes of the brain.

18.12 Transpetrous Approaches

In the presence of clival tumors with lateral extensions beyond the ICA or jugular foramen, adequate access for tumor resection may necessitate the use of a variety of transpetrous approaches. The amount of petrous bone resection is tailored to the location of the tumor. Anterior, posterior, or, rarely, total petrosectomy may be necessary.

An anterior petrosectomy will access tumor extensions in and around the petroclival synchondrosis, the posterior cavernous sinus, and the prepontine and cerebellopontine cisterns. The limits of bone removal include the carotid canal laterally, the superior petrosal sinus medially, the inferior petrosal sinus inferiorly, and the internal auditory canal and cochlea posteriorly.29 Sacrifice of the mandibular nerve and anterolateral displacement of the ICA allows further inferior exposure of the clivus.26 ^,​ 47 Although a few appropriately located small tumors can be resected through this surgical corridor, an anterior-based approach is typically required as a second stage for tumor extensions superolateral to the internal carotid artery.

Of the posterior transpetrous approaches, the petrosal or subtemporal–retrolabyrinthine approach is best suited for large posterolateral intradural tumor extensions, whereas the ITF approach can be used for both extra and intradural tumor extensions (Fig. 18.6).7 ^,​ 35 In the latter approach the structures of the jugular foramen can be identified and skeletonized using a high-speed drill. The extradural removal of tumors from around the exiting lower CNs can result in neurological improvement. The approach can be extended inferiorly by the posterior mobilization of the vertebral artery from the foramina transversaria of C1 and C2. In this way, the region of the odontoid process and arch of C1 can be exposed.10 ^,​ 23 ^,​ 24 ^,​ s. Literatur Craniospinal fixation may be necessary.

Total petrosectomy allows access from the sphenoid sinus to the foramen magnum and from the upper cervical spine to the intradural structures of the middle and posterior fossae. Destruction of the inner ear and complete mobilization of the facial nerve, with their attendant morbidities, are consequences of this approach. The problem of limited midline access remains.

18.13 Endonasal Endoscopic Transclival/Transpterygoid Approach

Taking advantage of the nasopharynx as a corridor, the endoscopic endonasal approaches provide direct access to the clivus with the theoretical benefit of reductions to both neurovascular manipulation and soft tissue morbidity. Particularly for clival malignancies, such as chordomas, the endoscopic transclival approach is now the preferred initial strategy of choice (Fig. 18.7). From the endoscopic standpoint, the clivus is divided into thirds in the craniocaudal direction, with clear anatomic considerations associated with each third. The lateral limits of the endoscopic transclival approach for each third of the clivus are the CNs of the cavernous sinus (upper third), the paraclival carotid arteries (middle third), and the Eustachian tubes (lower third). Within the subarachnoid space of the posterior fossa, the transclival approach provides the ability to manage disease along the ventral brainstem and vertebrobasilar system using standard microsurgical techniques; however, disease extension lateral to the abducens nerve is a clear limit of this approach. In this section, we will cover strategies for maximizing the endoscopic transclival approach for each third of the clivus to access disease within not only the clivus but also adjacent bony and soft tissue compartments.

18.13.2 Sinonasal Dissection

The first step of sinonasal dissection is the harvesting of a nasoseptal flap pedicled on the sphenopalatine artery. To ensure adequate coverage of not only the anticipated defect but also the exposed internal carotid arteries and bony skull base, the flap length and width are maximized by extending relevant incisions anteriorly toward the columella and laterally along the nasal floor toward the inferior turbinate, respectively. The flap is typically stored within the maxillary sinus. If an extremely large holoclival defect is anticipated, then bilateral nasoseptal flaps are harvested.

The paranasal sinuses are then opened selectively to provide sufficient access. At the very least, this consists of performing bilateral posterior ethmoidectomies and a wide sphenoidotomy with a view to identifying landmarks such as the orbital apex, opticocarotid recesses, and paraclival carotid arteries. For midclival access, to ensure sufficient lateral access to the internal carotid arteries, bilateral maxillary antrostomies may be performed along and the sphenopalatine foramina and the medial aspect of the pterygopalatine fossae opened. With subsequent transposition of the nasoseptal flap–sphenopalatine artery–pterygopalatine fossa complex, the vidian neurovascular bundle can be identified and sectioned. This maneuver can enhance the transpterygoid approach by avoiding the sacrifice of any intranasal flaps. To access the lower clival region, a U-shaped incision is made in the mucosa of the posterior nasopharynx. The underlying longus capitis muscle is dissected (or resected if there is tumor invasion) and reflected separately. After this initial approach, the sphenoid sinus floor is resected to the clivus and laterally to the vidian canals.

Related posts:

17 Nasopharyngeal Carcinoma 22 The Evaluation and Management of Sellar Tumors 28 Tumors of the Orbit 27 Tumors of the Craniovertebral Junction 23 Tumors of the Cavernous Sinus and Parasellar Space 24 Tumors of the Petrous Apex

Stay updated, free articles. Join our Telegram channel

Join