Faculty Bibliography

Objective When the use of the nasoseptal flap for endoscopic skull base reconstruction has been precluded, the posterior pedicle inferior turbinate flap is a viable option for small midclival defects. Limitations of the inferior turbinate flap include its small surface area and limited arc of rotation. We describe a novel extended inferior turbinate flap that expands the reconstructive applications of this flap. Design Cadaveric anatomical study. Participants Cadaveric specimens. Main Outcome Measures Flap size, arc of rotation, and reconstructive applications were assessed. Results The average width of the flap was 5.46 ± 0.58 cm (7.32 ± 0.59 cm with septal mucosa). The average length of the flap was 5.01 ± 0.58 cm (5.28 ± 0.37 cm with septal mucosa). The average surface area of the flap was ∼ 27.26 ± 3.65 cm(2) (40.53 ± 6.45 cm(2) with septal mucosa). The extended inferior turbinate flap was sufficient to cover clival defects extending between the paraclival internal carotid arteries. The use of the flap in 22 cadavers and 5 clinical patients is described. Conclusion The extended inferior turbinate flap presents an additional option for reconstruction of skull base defects when the nasoseptal flap is unavailable.

OBJECTIVES/HYPOTHESIS/OBJECTIVE:The eustachian tube (ET) is an important landmark in skull base surgery, which has a close relationship with the petrous segment of the internal carotid artery (ICA). The goal of the current study was to establish the detailed anatomic relationship of the ET and petrous segment of the ICA. STUDY DESIGN/METHODS:Anatomical study. METHODS:Six silicon-injected adult cadaveric heads (12 sides) were dissected using a lateral infratemporal fossa approach (type C) and endoscopic endonasal approach. The ET and ICA were exposed; their detailed relationships were demonstrated. High-quality pictures were obtained. RESULTS:In the anterior genu/foramen lacerum segment of the ICA, the vidian nerve was an important landmark. The cartilaginous ET was divided into four segments, from anterior to posterior: nasopharyngeal, pterygoid, lacerum, and petrosal segment. The anterior and inferior wall of the carotid canal was consistently between the horizontal ICA and petrous segment of the cartilaginous ET. In the posterior genu of the ICA, the bony part of the ET, and the tendon of the tensor tympani muscle were paramount landmarks. The posterior genu of the ICA was imbedded in the carotid canal. The landmarks of the junction of the cartilaginous ET and bony ET were the sphenoid spine and foramen spinosum. CONCLUSIONS:The anatomical segmentation of the ET provides the basis for safe and effective transection of the ET in skull base surgery. An understanding of the complex relationships of the ET and petrous segment of the ICA is paramount for surgically dealing with disease located within the region of the ET and petrous segment of the ICA. LEVEL OF EVIDENCE/METHODS:NA

Objectives To present and validate a chicken wing model for endoscopic endonasal microsurgical skill development. Setting A surgical environment was constructed using a Styrofoam box and measurements from radiological studies. Endoscopic visualization and instrumentation were utilized in a manner to mimic operative setting. Design Five participants were instructed to complete four sequential tasks: (1) opening the skin, (2) exposing the main artery in its neurovascular sheath, (3) opening the neurovascular sheath, and (4) separating the nerve from the artery. Time to completion of each task was recorded. Participants Three junior attendings, one senior resident, and one medical student were recruited internally. Main Outcome Measures Time to perform the surgical tasks measured in seconds. Results The average time of the first training session was 48.8 minutes; by the 10th training session, the average time was 22.4 minutes. The range of improvement was 25.7 minutes to 72.4 minutes. All five participants exhibited statistically significant decrease in time after 10 trials. Kaplan-Meier analysis revealed that an improvement of 50% was achieved by an average of five attempts at the 95% confidence interval. Conclusions The ex vivo chicken wing model is an inexpensive and relatively realistic model to train endoscopic dissection using microsurgical techniques.

The nasoseptal flap had an important role in the development of endoscopic endonasal surgery of the cranial base. The flap is pedicled upon the posterior septal artery, which is a terminal branch of the sphenopalatine artery. The reliable vascular supply promotes rapid healing and the flap is an effective barrier for the prevention of CSF leaks. For large skull base defects, it has dramatically decreased the risk of a postoperative CSF leak to less than 5%. The nasoseptal flap is a versatile flap with a wide arc of rotation that allows the flap to reach defects from the frontal sinus to the lower clivus. This chapter provides a comprehensive review of the nasoseptal flap. The harvesting and reconstruction techniques, modifications of the flap and complications are described.

Objective Reconstruction of large clival defects after an endoscopic endonasal procedure is challenging. The objective is to analyze the morphology, indications, and limitations of the extended nasoseptal flap, which adds the nasal floor and inferior meatus mucosa, compared with the standard nasoseptal flap, for clival reconstruction. Design Twenty-seven sides of formalin-fixed anatomical specimens and 13 computed tomography (CT) scans were used. Under 0-degree endoscopic visualization, a standard flap on one side and an extended flap on the other side were performed, as well as exposure of the sella, cavernous sinus, and clival dura mater. Coverage of both flaps was assessed, and they were incised and extracted for measurements. Results The extended flap has two parts: septal and inferior meatal. The extended flaps are 20 mm longer and add 774 mm(2) of mucosal area. They cover a clival defect from tuberculum to foramen magnum in 66.6% cases and from below the sella in 91.6%. They cover both parasellar and paraclival segments of the internal carotid arteries. The lateral inferior limits are the medial aspect of the hypoglossal canals and Eustachian tubes. CT scans can predict the need or limitation of an extended nasoseptal flap. Conclusions The nasal floor and inferior meatus mucosa adds a significant area for reconstruction of the clivus. A defect laterally beyond the hypoglossal canals is not likely covered with this variation of the flap. Preoperative CT scans are useful to guide the reconstruction techniques.

BACKGROUND:The posterior pedicle nasoseptal flap has been the workhorse for endoscopic reconstruction of medium to large cranial base defects, with excellent outcomes and minimal flap failures. The authors present the anatomical foundations for the use of the nasoseptal flap for reconstruction of soft palate and pharyngeal defects and for surgical treatment of velopharyngeal insufficiency in a cadaveric model. METHODS:Posterior pedicle nasoseptal flaps were endoscopically harvested and transposed to the naso/oropharynx in seven cadavers. The reach and relationships of the flap with nasopharyngeal and oropharyngeal structures were documented. RESULTS:A total of nine nasoseptal flaps (bilateral in two specimens) were transposed into the nasopharynx and oropharynx. The most anterior aspect of the flap was visualized transorally several millimeters inferior to the soft palate in all specimens. Six flaps were sutured transorally to the posterior pharyngeal wall and three were sutured to defects of the soft palate. The width of a fully harvested flap (entire septal mucosa) was more than twice the width of the posterior nasopharyngeal/oropharyngeal wall in all specimens. Nasoseptal flaps were easily tailored endoscopically and transorally with standard instrumentation to fit the defects. CONCLUSIONS:In a cadaveric model, the nasoseptal flap can be transposed into the nasopharynx and upper oropharynx and is a potential alternative for pharyngeal reconstruction and surgical treatment of velopharyngeal insufficiency in patients in whom traditional flaps are not available. The application of this technique for reconstruction of pharyngeal and velar defects is novel, and further studies evaluating clinical outcomes are needed.

Objectives Infraorbital nerve (ION) decompression, excision to remove intrinsic tumors, and resection with oncological margins in malignancies with perineural invasion or dissemination are usually accomplished with an open approach. The objective is to describe the surgical anatomy, technique, and indications of the endonasal endoscopic approach (EEA) to the ION with nasolacrimal duct preservation. Design Eleven sides of formalin-fixed specimens were dissected. An anterior maxillary antrostomy was performed. The length of the ION prominence within the sinus and anatomic features of the covering bone were studied. A 45-degree endoscope visualized the infraorbital prominence endonasally. An angled dissector and dural blade allowed for dissection and resection of the ION ipsilaterally and contralaterally. Results The bone features of the ION prominence allowed for ipsilateral dissection in 10 out of 11 sides. In one case with the ION surrounded by thick cortical bone, the dissection could only be started by drilling contralaterally. The 45-degree endoscope visualized 92.2% and 100% of the length of the nerve using the ipsilateral and contralateral nostrils, respectively. Ipsilaterally, 83% of its length was resected, and 96.3% was resected contralaterally. Conclusion The ION can be approached using an ipsilateral EEA with nasolacrimal duct preservation in most cases. The contralateral approach provides a wider angle to access the ION. This technique is primarily indicated in cases where the EEA can be used for tumor resection and oncological margins within the ION.

Introduction Complete or partial removal of the pterygoid process provides lateral extension of the endonasal corridor necessary to approach the Meckel cave, infrapetrous skull base, and medial infratemporal fossa. This paper provides the anatomical foundations for the endoscopic endonasal transpterygoid approach with preservation of all neurovascular structures inside the pterygopalatine fossa. Methods Eight endoscopic transpterygoid approaches were performed in fresh cadaveric specimens. In all dissections the vidian nerve and the periosteal sac enclosing the pterygopalatine fossa were preserved. Results We reliably transposed the pterygopalatine fossa to approach the Meckel cave, infrapetrous skull base, and medial infratemporal region, preserving the neurovascular structures inside the pterygopalatine fossa in all specimens. Conclusions The transposition of the pterygopalatine fossa neurovascular structures for endoscopic endonasal approaches to the skull base is an alternative technique that is both feasible and desirable. The transposition requires no additional technical skills but requires comprehensive knowledge of its anatomy. The anatomical preservation of the neurovascular structures is potentially beneficial to the quality of life of patients. Clinical studies are necessary to prove the real benefits of this technique.

OBJECTIVES/HYPOTHESIS/OBJECTIVE:To evaluate the transoral anatomy of the tonsillar fossa and lateral pharyngeal wall and to correlate these findings with radiographic measurements and transoral robotic surgery (TORS) of patients with early tonsillar tumor. STUDY DESIGN/METHODS:Preclinical cadaveric study and patient cohort. METHODS:Six complete cadaveric dissections were performed to identify key anatomic landmarks, and these landmarks were validated in two consecutive patients with T1 human papillomavirus-positive squamous cell carcinoma of the tonsil treated by TORS. For radiographic landmark analysis, 25 patients who underwent contrast-enhanced computed tomography (CT) of the neck for a variety of endoscopic skull base procedures were selected. Measurements were taken from the lateral pharyngeal wall at C2-C3 interspace and greater horn of hyoid (C6) to the external carotid artery (ECA). RESULTS:The glossopharyngeal (IX) nerve was consistently identified deep to the superior constrictor musculature and at the intersection of the posterior tonsillar pillar with the base of tongue. The styloglossus muscle forms the deep plane medial to the ECA. The mean measurements for left C2-C3 interspace to the ECA and right C2-C3 interspace to ECA were 17.6 ± 0.8 mm and 18.4 ± 0.8 mm, respectively. Similarly, the mean measurements for left hyoid to ECA and right hyoid to ECA were 3.4 ± 0.8 mm and 4.3 ± 0.6 mm, respectively. CONCLUSIONS:A systematic approach to dissect the tonsillar fossa and lateral pharyngeal wall can be performed using key anatomic landmarks. CT measurements taken at the C2-C3 interspace and greater horn of hyoid bone (C6 level) to the ECA are consistently and reliably achieved.