Combined anterior cranial base resection is the mainstay of therapy for skull base malignancies. Improvements in surgical techniques and reconstruction have led to a reduction in morbidity and overall better survival rates. Meticulous attention to dural and skull base reconstruction is essential for reducing the major complications, including cerebrospinal fluid leak and pneumocephalus. Complications can be devastating, but timely effective management can limit the severity.
Key points
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Combined craniofacial resection remains the most effective approach for skull base malignancies, despite the evolution of endonasal endoscopic techniques.
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Meticulous dural reconstruction and skull base repair limit the major complications associated with craniofacial resections.
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Effective management of complications, such as CSF leak and pneumocephalus, limit the morbidity from these operations.
Introduction
The application of the combined craniofacial approach for skull base malignancies was first described by Ketcham, and colleagues in 1963. Techniques have evolved significantly since the original description, but the basic premise of gross total resection with negative margins remains the goal of therapy. Technical advances in resection and reconstruction, improvements in intensive care management, and triple antibiotic therapy have reduced complications and allowed for the safe removal of anterior cranial base malignancies that involve not only the anterior skull base, but also the orbit, brain, and infratemporal fossa. The evolution of anterior cranial base surgery integrated with advanced imaging and adjuvant radiation and chemotherapy have shown improved outcomes over the last 2 decades. Gil and colleagues reported a significant improvement in overall survival and disease-specific survival in patients who have undergone surgery since 1996 compared with those who underwent resection from 1973–1996. Of 106 patients operated on before 1996, the 5-year overall survival and disease-specific survival rates were 55% and 57%, respectively, whereas they improved to 66% and 70%, respectively, for the 176 patients in their series who were treated from 1996–2008. Despite advances in surgery, poor prognostic indicators include positive surgical margins, unfavorable tumor histologies (eg, squamous cell carcinoma, melanoma, high-grade sarcoma), intracranial or orbital invasion, and prior radiation therapy.
Despite the evolution of purely endonasal endoscopic techniques, the combined craniofacial techniques continue to be the gold standard and principle strategy in treatment of anterior and anterolateral skull base malignancies. The obvious benefits of purely endoscopic techniques include less soft-tissue dissection and avoidance of the morbidity associated with a craniotomy and brain retraction ; however, these benefits may be more relevant for benign skull base tumors than for extensive skull base malignancies. Malignant tumors often present significant anatomic constraints to effective endoscopic resection because of involvement of neurovascular structures, optic nerves, and infiltration into the brain, orbit, or infratemporal fossa. Additionally, endoscopic resection obviates not only the ability to achieve en bloc resection for negative margins, but also necessitates dissecting through tumor to identify normal structures. Conversely, the craniofacial approach allows the identification of normal structures first rather than intralesionally dissecting through tumor to identify critical anatomy and normal tissue planes. The ability to separate the nasal cavity from the intradural compartment is limited via an endoscopic approach because of the frequent need to use a nasoseptal flap for reconstruction. The nasal septum often is resected in the treatment of malignancies because of tumor involvement or to achieve negative margins. Finally, clinical series showing improved local control with endoscopic techniques are not comparable with regard to prognostic categories based on tumor histologies. In a report from Eloy and colleagues, local recurrence rates were 5.6% in the endoscopic group compared with 29.2% for the craniofacial cohort, which approached significance ( P = .051). However, a lack of equipoise was demonstrated, as most patients in the endoscopic group had favorable prognostic histologies (eg, esthesioneuroblastoma, small cell carcinoma) compared with the craniofacial groups with poor prognostic histologies (eg, squamous cell carcinoma, high-grade sarcomas). Soler and Smith reviewed published data on endoscopic compared with craniofacial techniques for esthesioneuroblastoma. Short-term control rates seem to be equivalent, but endoscopic techniques are typically reserved for lower-stage tumors.
It is critical that surgeons treating skull base malignancies continue to understand the techniques and reconstructive strategies of combined anterior craniofacial approaches. The integration of endoscopic endonasal dissection is becoming more prevalent but has not currently replaced the need for a combined anterior cranial base approach. This article reviews the nuances of anterior and anterolateral resection of skull base malignancies and complication avoidance and management.
Introduction
The application of the combined craniofacial approach for skull base malignancies was first described by Ketcham, and colleagues in 1963. Techniques have evolved significantly since the original description, but the basic premise of gross total resection with negative margins remains the goal of therapy. Technical advances in resection and reconstruction, improvements in intensive care management, and triple antibiotic therapy have reduced complications and allowed for the safe removal of anterior cranial base malignancies that involve not only the anterior skull base, but also the orbit, brain, and infratemporal fossa. The evolution of anterior cranial base surgery integrated with advanced imaging and adjuvant radiation and chemotherapy have shown improved outcomes over the last 2 decades. Gil and colleagues reported a significant improvement in overall survival and disease-specific survival in patients who have undergone surgery since 1996 compared with those who underwent resection from 1973–1996. Of 106 patients operated on before 1996, the 5-year overall survival and disease-specific survival rates were 55% and 57%, respectively, whereas they improved to 66% and 70%, respectively, for the 176 patients in their series who were treated from 1996–2008. Despite advances in surgery, poor prognostic indicators include positive surgical margins, unfavorable tumor histologies (eg, squamous cell carcinoma, melanoma, high-grade sarcoma), intracranial or orbital invasion, and prior radiation therapy.
Despite the evolution of purely endonasal endoscopic techniques, the combined craniofacial techniques continue to be the gold standard and principle strategy in treatment of anterior and anterolateral skull base malignancies. The obvious benefits of purely endoscopic techniques include less soft-tissue dissection and avoidance of the morbidity associated with a craniotomy and brain retraction ; however, these benefits may be more relevant for benign skull base tumors than for extensive skull base malignancies. Malignant tumors often present significant anatomic constraints to effective endoscopic resection because of involvement of neurovascular structures, optic nerves, and infiltration into the brain, orbit, or infratemporal fossa. Additionally, endoscopic resection obviates not only the ability to achieve en bloc resection for negative margins, but also necessitates dissecting through tumor to identify normal structures. Conversely, the craniofacial approach allows the identification of normal structures first rather than intralesionally dissecting through tumor to identify critical anatomy and normal tissue planes. The ability to separate the nasal cavity from the intradural compartment is limited via an endoscopic approach because of the frequent need to use a nasoseptal flap for reconstruction. The nasal septum often is resected in the treatment of malignancies because of tumor involvement or to achieve negative margins. Finally, clinical series showing improved local control with endoscopic techniques are not comparable with regard to prognostic categories based on tumor histologies. In a report from Eloy and colleagues, local recurrence rates were 5.6% in the endoscopic group compared with 29.2% for the craniofacial cohort, which approached significance ( P = .051). However, a lack of equipoise was demonstrated, as most patients in the endoscopic group had favorable prognostic histologies (eg, esthesioneuroblastoma, small cell carcinoma) compared with the craniofacial groups with poor prognostic histologies (eg, squamous cell carcinoma, high-grade sarcomas). Soler and Smith reviewed published data on endoscopic compared with craniofacial techniques for esthesioneuroblastoma. Short-term control rates seem to be equivalent, but endoscopic techniques are typically reserved for lower-stage tumors.
It is critical that surgeons treating skull base malignancies continue to understand the techniques and reconstructive strategies of combined anterior craniofacial approaches. The integration of endoscopic endonasal dissection is becoming more prevalent but has not currently replaced the need for a combined anterior cranial base approach. This article reviews the nuances of anterior and anterolateral resection of skull base malignancies and complication avoidance and management.
Combined anterior craniofacial resection
Imaging
Both magnetic resonance (MR) imaging and computed tomography (CT) scans are helpful in preoperative planning to define the extent of tumor and type of resection required. CT scans are useful for defining the myriad of anatomic variability in bone anatomy, including the size of the frontal sinus and crista galli, location of bony septae, length of the planum sphenoidale, and degree of bone erosion. The MR is important for tumor identification and the relationship to critical structures. The extent of resection and type of reconstruction is determined principally based on MR imaging. Contraindications to surgical resection can be evaluated, including extensive cavernous sinus involvement and involvement of the only sighted eye. However, even high-resolution MR may not provide enough detail to make preoperative decisions regarding periorbital invasion, which may require orbital exenteration or penetration of the skull base dura. Decisions regarding these issues may still require highly skilled intraoperative judgment and extensive informed consent. The propensity for some tumors to present with regional or distant metastases also plays a major role in determining treatment. A screening body scan, such as positron emission tomography or CT, is important for staging before treatment.
Preoperative Biopsy
Definitive preoperative pathologic diagnosis of anterior skull base malignancies is critical to decisions regarding treatment. Most biopsies can be done endoscopically by head and neck surgeons in the office, but occasionally deep lesions undergo biopsy in the operating room. Tumor management is highly dependent on whether the pathology results are benign or malignant and the relative responsiveness to radiation or chemotherapy. Malignant tumors such as lymphoma and rhabdomyosarcoma are treated with chemotherapy either as definitive therapy or as neoadjuvant treatment. Other tumors, such as squamous cell carcinoma, adenoid cystic carcinoma, sarcoma and melanoma are best treated with resection.
Surgery
Preparation
After induction of general anesthesia, the endotracheal tube should be positioned opposite the site of the lateral rhinotomy or the epicenter of the tumor. The eyelids are sutured, but the suture should be placed so that the pupils can be readily examined at surgery. A spinal drain is placed for intermittent drainage throughout the procedure to facilitate brain relaxation and for use in the postoperative period to ensure a water-tight closure. Triple antibiotic therapy (metronidazole ceftazidime, vancomycin) is initiated at the induction of anesthesia. The preparation should take into account all possible facial incisions and the need for a free flap.
Surgical technique
Craniotomy and Galeal Pericranial Graft: Smaller and Longer, Respectively
The head is positioned on a foam donut. A bicoronal incision is fashioned between the zygomas over the vertex of the skull starting 1.5 cm anterior the ear after injection of the skin with 1% lidocaine with epinephrine. The skin is incised with a 10 blade taking care to preserve the pericranium, which initially remains attached to the scalp. A hemostat is used to define the plane between the galea and pericranium. The superficial temporary arteries are preserved for possible free flap anastomosis at the end of the operation. A subgaleal dissection of the posterior skin flap is accomplished extending to the posterior parietal bone. The posterior pericranium is incised at this point with the Bovie cautery, and a subperiosteal dissection with a broad periosteal elevator is accomplished to the level of the supraorbital rims and nasion. The galea is then dissected from the anterior scalp flap beginning 1 cm anterior to the incision to facilitate subsequent galeal closure. The galeal-pericranial graft is harvested with a 15 blade, creating a long vascularized graft for skull base reconstruction. This flap is wrapped in bacitracin-soaked gauze and retracted with blunt hooks ( Fig. 1 ).
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