Endoscopic Craniofacial Resection




Abstract


An endoscopic craniofacial resection (CFR) can be considered in the management of benign and malignant tumors of the paranasal sinuses involving the skull base and may avoid the morbidity associated with an open CFR. A standard CFR combines a transfacial approach via a lateral rhinotomy or midface degloving to remove the sinus tumor components with a transcranial approach to remove the skull base and intracranial portions of the tumor. An endoscopic approach allows for a magnified view and increased illumination compared to a standard approach, especially in deep areas such as the pterygoid palatine fossa and the sphenoid sinus. The rate of postoperative CSF leak in endoscopic CFR is usually below 10%, and studies have found no difference in survival, metastatic, or complication rates between the two approaches.




Keywords

endoscopic craniofacial resection, endoscopic sinus surgery, esthesioneuroblastoma, sinonasal tumor, skull base surgery, skull base tumor

 




Introduction





  • Endoscopic craniofacial resection (CFR) has emerged as an alternative to the traditional CFR originally credited to Ketcham in 1963.



  • The standard craniofacial approach for tumor resection combines a transfacial approach via a lateral rhinotomy or midface degloving to gain access for removal of the sinus component of the tumor with a transcranial approach to remove the skull base and intracranial portion of the tumor. The most common indications for CFR are tumors arising from the nasal cavity, frontal sinuses, or ethmoid sinuses extending to or through the anterior skull base.



  • The major reason for selecting endoscopic CFR is to avoid the morbidity associated with open CFR.



  • The rates of complication associated with open CFR as reported in the literature vary considerably.




    • In the largest study to date evaluating open CFRs, Ganly et al. reported an overall complication rate of 36.3% and a mortality rate of 4.7%.



    • The rate of CSF fistula after major CFR may be as high as 20%.



    • The rate of meningitis after CFR is reported in the literature to be 5% to 7.7%.




  • Despite the wide exposure afforded by the open CFR, the close proximity of the orbit, brain, and other critical neurovascular structures often prevents surgeons from taking large margins without causing significant morbidity. In fact, one multicenter study looking at outcomes of open CFRs reported a 30% incidence of positive margins.



  • It has been suggested that the magnified view provided by the endoscope can also make tumor mapping more precise, especially in deep areas such as the pterygopalatine fossa and sphenoid sinus, where visualization and illumination can be difficult in an open procedure. Furthermore, for some tumors, unilateral endoscopic resection is possible, thus preserving smell on the contralateral side.



  • A major criticism of endoscopic CFR is that the tumors are removed piecemeal. Traditional teaching is that tumors should be removed en bloc to ensure maximal survival. This principle is founded on the concept that surgical violation of the tumor predisposes to spread of the cancer through lymphatic or vascular channels, thereby increasing the risk of local, regional, and distant tumor spread. Furthermore, there is concern that tumor removal is more likely to be incomplete with a piecemeal as opposed to an en bloc resection. However, data from transoral laser microsurgery and transoral robotic surgery, as well as more recent data from endoscopic CFRs, show that this is not the case. The most important surgical variable affecting survival, regardless of the method used, is achieving complete tumor resection with negative margins.



  • A study comparing endoscopic versus open craniofacial resection found no significant differences in survival, metastatic rates, or complication rates between the two groups. The endoscopic group had shorter hospital stays and the added benefit of a better cosmetic outcome. However, comparison of oncologic outcomes between the groups was limited by discrepancy in histologic grade and clinical stage between the two retrospective, nonrandomized groups.





Anatomy





  • Surgery of the skull base is complex because of its proximity to the dura, brain, and orbit. Tumors will be adjacent to or involve one or more of these structures during endoscopic CFR.



  • Sphenoid sinus anatomy deserves special mention. The optic nerve and cavernous sinus are located along the lateral wall, whereas the sella turcica is located posteriorly and centrally.



  • Refer to the appropriate chapters in this text for more detailed anatomic descriptions of the sphenoid sinus, ethmoid roof, and frontal sinus.





Preoperative Considerations





  • Endoscopic CFR may be considered in the management of benign and malignant tumors of the paranasal sinuses involving the skull base.



  • This chapter focuses on the treatment of esthesioneuroblastoma, which is one of the more common tumors approached by this method. However, this technique can be applied to the majority of benign and malignant tumors involving the anterior skull base.



  • Preoperative images should be thoroughly analyzed; the findings will ultimately determine tumor resectability and critical anatomic constraints.



  • A multidisciplinary approach—including, when pertinent, specialists in neurosurgery, ophthalmology, medical oncology, and radiation oncology—is critical.



  • A definitive tissue biopsy is necessary preoperatively, especially when critical anatomic structures such as the orbit, dura, or neurovascular regions are involved.



  • Indications include any benign or malignant tumor of the nasal cavity and/or paranasal sinuses that involves the anterior skull base.



  • Contraindications include poor surgical candidacy because of comorbidities, involvement of skin or brain parenchyma, and bilateral orbital involvement.



  • Relative contraindications include extension into the cavernous sinus, orbit, and lacrimal system, as well as massive tumors with unfavorable histologic features. Another contraindication to the approach is the inability to reconstruct the skull base due to factors such as previous surgery, radiation exposure, or defect size.



Workup and Staging





  • Esthesioneuroblastoma, first described by Berger and Luc in 1924, arises from the olfactory epithelium and accounts for approximately 3% to 6% of malignancies of the nasal cavity and paranasal sinus.



  • Tumor staging is an important guide for prognosis and therapy. The most common staging systems are the Kadish staging system ( Table 25.1 ), the University of California at Los Angeles–Dulguerov and Calcaterra staging system ( Table 25.2 ), and the Hyams histopathologic grading system ( Table 25.3 ). In a 1993 study by Morita et al. examining prognostic factors, Hyams histopathologic grade was found to be the most significant prognostic factor, with a 5-year survival rate of 80% for 32 patients with low-grade tumors and 40% for 15 patients with high-grade tumors.



    TABLE 25.1

    Kadish Staging System
















    Stage Characteristics
    A Disease confined to nasal cavity
    B Disease in nasal cavity and one or more paranasal sinuses
    C Disease extending beyond the nasal cavity and paranasal sinuses


    TABLE 25.2

    UCLA–Dulguerov and Calcaterra TNM Staging































    Stage Characteristics
    T1 Tumor involving the nasal cavity and/or paranasal sinuses (excluding sphenoid), sparing the most superior ethmoid cells
    T2 Tumor involving the nasal cavity and/or paranasal sinuses (including the sphenoid) with extension to or erosion of the cribriform plate
    T3 Tumor extending into the orbit or protruding into the anterior cranial fossa, without dural invasion
    T4 Tumor involving the brain
    N0 No cervical lymph node metastasis
    N1 Any form of cervical lymph node metastasis
    M0 No metastases
    M1 Distant metastasis

    TNM, Tumor, node, metastases; UCLA, University of California at Los Angeles.


    TABLE 25.3

    Hyams Histopathologic Grading












































    Grade Lobular Architecture Preservation Mitotic Index Nuclear Polymorphism Fibrillary Matrix Rosettes Necrosis
    I + None None Prominent HW rosettes None
    II + Low Moderate Present HW rosettes None
    III +/− Moderate Prominent Low FW rosettes Rare
    IV +/− High Marked Absent None Frequent

    FW, Flexner-Wintersteiner; HW, Homer Wright.



Radiographic Considerations





  • Before endoscopic CFR, the primary tumor site must be examined using magnetic resonance imaging (MRI) and computed tomography (CT). The scans should be analyzed closely for involvement of the eye, dura, brain, and neurovascular structures ( Fig. 25.1 ). As with any oncologic surgery, the goal of endoscopic CFR is to achieve clear margins. If this goal cannot be achieved, then other approaches should be used. For advanced-stage sinonasal malignancies, a workup for metastasis should include examination of the neck and lungs. Consideration can be given to performing positron emission tomography instead of neck and chest CT.




    Fig. 25.1


    Tumor extent is the main determinant of the feasibility of performing an endoscopic craniofacial resection (CFR) with successful complete tumor resection. (A) Coronal T1-weighted contrast-enhanced magnetic resonance image (MRI) of a sinonasal mass with massive intracranial extension (single asterisks) and periorbital involvement (double asterisks). This tumor, with its wide dural involvement, would be better treated using an open craniotomy approach. (B) Coronal MRI of a different paranasal mass. Note that this mass also invades the periorbita as well as the dura but still may be amenable to endoscopic CFR.

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Feb 1, 2019 | Posted by in OTOLARYNGOLOGY | Comments Off on Endoscopic Craniofacial Resection
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