Chondrosarcomas of the skull base are rare, locally invasive tumors that typically arise in the petroclival region, from degenerated chondroid cells located within the synchondrosis. Given their usually slow growth rate, they are capable of reaching sizable dimensions, promoting bone erosion and significant displacement of neurovascular structures before causing symptomatology that will eventually lead to diagnosis; cranial neuropathies and headaches are common complaints. This article discusses the pertinent surgical anatomy, patient selection criteria, technical nuances and complication management of the endonasal resection of skull base chondrosarcomas.
Key points
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Skull base chondrosarcomas are locally aggressive and arise from the petroclival synchondrosis to involve multiple surrounding regions.
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Despite local aggressiveness, they often “respect” the dura, displacing rather than transgressing it like other skull base malignancies.
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Although the dura is often intact at the end of tumor resection, elevating a vascularized nasoseptal flap is still a key portion of the procedure to protect the exposed internal carotid artery (ICA).
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A standard wide transsphenoidal approach is coupled with other modules of the expanded endoscopic endonasal approaches, according to tumor characteristics.
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From its main component in the petroclival synchondrosis, the tumor may be “followed” into the cavernous sinus, Meckel’s cave, the middle and posterior cranial fossae, and the craniovertebral junction.
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Removal of the posterior wall of the maxillary sinus grants access to the pterygopalatine fossa; locating the vidian nerve within it and tracing its path posteriorly will lead to the foramen lacerum and the transition between the petrous and paraclival portions of the ICA.
Introduction
Chondrosarcomas of the skull base are rare, locally invasive tumors that typically arise in the petroclival region, from degenerated chondroid cells located within the synchondrosis. Given their usually slow growth rate, they are capable of reaching sizable dimensions, promoting bone erosion and significant displacement of neurovascular structures before causing symptomatology that will eventually lead to diagnosis; cranial neuropathies and headaches are common complaints. From the petroclival region, they may invade the upper clivus and cavernous sinus superiorly, Meckel’s cave and the medial middle cranial fossa laterally, the posterior cranial fossa medially and posteriorly, and the craniovertebral junction inferiorly. Moreover, chondrosarcomas have been shown to spill into the infratemporal fossa and the high cervical region, infiltrating the jugular foramen and even the jugular vein. Despite this local aggressiveness, these lesions often spare the dura, compressing and displacing rather than transgressing it. This behavior, coupled with their ability to affect multiple cranial compartments simultaneously, renders the ventral transnasal corridor particularly appealing for their surgical management. Due to their ventral trajectory, potential advantages of endoscopic endonasal approaches (EEAs) include the possibility of accessing multiple skull base compartments, even bilaterally, in a single procedure while avoiding retraction or manipulation of neurovascular structures; this is exceptionally displayed during endonasal resection of chondrosarcomas.
Hence, herein the authors describe their indications, contraindications, surgical technique and anatomy, complication management, and perioperative care for the endoscopic endonasal resection of skull base chondrosarcomas. Nevertheless, one must be aware that this is a heterogeneous group that may present in a wide variety of scenarios; thus, we will focus on describing the rationale behind surgically addressing those lesions located mainly in the petroclival region with involvement of neighboring compartments.
Introduction
Chondrosarcomas of the skull base are rare, locally invasive tumors that typically arise in the petroclival region, from degenerated chondroid cells located within the synchondrosis. Given their usually slow growth rate, they are capable of reaching sizable dimensions, promoting bone erosion and significant displacement of neurovascular structures before causing symptomatology that will eventually lead to diagnosis; cranial neuropathies and headaches are common complaints. From the petroclival region, they may invade the upper clivus and cavernous sinus superiorly, Meckel’s cave and the medial middle cranial fossa laterally, the posterior cranial fossa medially and posteriorly, and the craniovertebral junction inferiorly. Moreover, chondrosarcomas have been shown to spill into the infratemporal fossa and the high cervical region, infiltrating the jugular foramen and even the jugular vein. Despite this local aggressiveness, these lesions often spare the dura, compressing and displacing rather than transgressing it. This behavior, coupled with their ability to affect multiple cranial compartments simultaneously, renders the ventral transnasal corridor particularly appealing for their surgical management. Due to their ventral trajectory, potential advantages of endoscopic endonasal approaches (EEAs) include the possibility of accessing multiple skull base compartments, even bilaterally, in a single procedure while avoiding retraction or manipulation of neurovascular structures; this is exceptionally displayed during endonasal resection of chondrosarcomas.
Hence, herein the authors describe their indications, contraindications, surgical technique and anatomy, complication management, and perioperative care for the endoscopic endonasal resection of skull base chondrosarcomas. Nevertheless, one must be aware that this is a heterogeneous group that may present in a wide variety of scenarios; thus, we will focus on describing the rationale behind surgically addressing those lesions located mainly in the petroclival region with involvement of neighboring compartments.
Indications/Contraindications
For indications and contraindications please refer to Table 1 .
| Indications | Contraindications | |
|---|---|---|
| Relative | Absolute | |
|
|
|
a Treat for 3 weeks (if bacterial) or 6 weeks (if fungal) before proceeding with endonasal surgery.
Surgical anatomy
The surgical anatomy of the petroclival region and its surroundings, as well as of the related endonasal approaches, has been described. The key landmarks and structures from a ventral perspective are illustrated in Fig. 1 .
Surgical technique
Preoperative Planning
All patients undergoing endonasal resection of a petroclival chondrosarcoma are submitted to the following:
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Anesthesia evaluation with nasal swab and culture; all patients are treated on the morning of surgery with a single nasal application of a povidone-iodine solution at 5% (3M, St. Paul, MN); if positive for methicillin-resistant Staphylococcus aureus (MRSA), the patients also receive vancomycin during induction.
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Magnetic resonance imaging (MRI) of the brain and computed axial tomography (CT) scan, both thinly sliced (<3 mm) and fused for intraoperative navigation. Special attention is given to the relation of the tumor to the different segments of the internal carotid artery (ICA); this characteristic will ultimately dictate which EEA modules must be performed during tumor resection.
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Otolaryngology evaluation, to detect sinonasal abnormalities, especially signs of infection.
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Evaluation by the speech therapy/swallowing disorders team in case of jugular foramen involvement.
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Audiometry in case of involvement of the cerebellopontine angle, internal acoustic canal and/or cranial nerve VII/VIII complex.
Preparation and Patient Positioning
Preparation
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General anesthesia with orotracheal intubation.
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Prophylactic antibiotics: cefepime if MRSA negative, cefepime and vancomycin if positive.
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Urinary catheter placement.
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Copious nasal irrigation with oxymetazoline hydrochloride solution and facial/nasal decontamination with iodine solution; the abdomen and the right thigh are also prepped in case fat or muscle grafts are necessary, respectively.
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Insertion of intraoperative monitoring needles according to tumor characteristics (cavernous sinus/cerebellopontine angle/jugular foramen involvement).
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The navigation tower and at least 2 monitors are positioned according to the otolaryngologist’s hand dominance ( Fig. 2 ).
Fig. 2
Patient and room positioning. ( A , B ) The patient’s head is secured on a Mayfield 3-pin headholder and turned to the right with slight neck extension; the body is secured with tape and protected with foam. Note the intraoperative monitoring needles; the abdomen and thigh are also prepped for possible grafts. ( C ) Room setup for a right-handed otolaryngologist; a monitor is positioned at the head of the patient and a second one at the feet, allowing both surgeons to stand to the right side of the patient. ( D ) Room setup for a left-handed otolaryngologist; 2 monitors are positioned at the head of the patient with the navigation tower between, allowing the surgeons to stand opposite each other on both sides of the patient.
Positioning
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Supine position, with the head fixed on the Mayfield 3-pin headholder. The neck is slightly extended and the head turned to the right, with the whole body tilted to the left (see Fig. 2 ). The right thigh is slightly flexed and rotated inward. The body is secured and protected with foam and tape; the navigation transmitter is attached to the headholder.
Surgical Approach
The surgical approach is composed of the following sequential steps ( Fig. 3 ):
- 1.
Right middle turbinectomy, performed with strong sinus scissors; extreme care is taken to avoid avulsing the turbinate from its insertion in the anterior cranial base and causing an early cerebrospinal fluid (CSF) leak.
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Bilateral posterior ethmoidectomies, performed with microdebriders.
- 3.
Elevation of the nasoseptal flap on the contralateral side of the lesion (a transpterygoid approach will ultimately dictate sacrificing the flap’s blood supply). The flap is usually stored on the ipsilateral maxillary sinus to allow ample maneuvering within the lower clivus/craniovertebral junction regions.
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Posterior septectomy.
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Incision and rotation of the now-exposed contralateral septal mucosa to cover the denuded septum.
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Drilling of the sphenoid floor until flush with the clivus.
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Removal of the posterior wall of the maxillary sinus on the tumor side, thus accessing the pterygopalatine fossa.
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Identification of the pterygopalatine ganglion, infraorbital, and vidian nerves.
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Progressive drilling of the vidian canal from anterior to posterior; depending on the amount of tumor lateral extension and the degree of pneumatization of the lateral sphenoid recess, the nerve may be spared or sacrificed during this step.
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The vidian nerve will ultimately lead the surgeon to the transition between the horizontal/petrous and vertical/paraclival segments of the ICA, at the foramen lacerum.
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Drilling of the clivus (clival removal is dictated by the amount of tumor in the posterior fossa); during this step, the team must be prepared to encounter massive venous bleeding from invasion of the basilar plexus, which can be managed with direct infusion of various clot-inducing products.
- 12.
Drilling of the petrous apex and skeletonization of the ICA.
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Endoscopic Endonasal Repair of Spontaneous and Traumatic Cerebrospinal Fluid Rhinorrhea
Surgical Techniques for Sinonasal Malignancies
Endoscopic Endonasal Approach to Ventral Posterior Fossa Meningiomas
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