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Introduction: Cerebrospinal fluid (CSF) leak occurs in 1-11% of endoscopic Draf III, or endoscopic modified Lothrop, procedures. CSF leak can occur during surgery during a superior nasal septectomy. This study investigated whether the posterior edge of the nasofrontal beak (NFB) at the level of the internal frontal ostium is a safe landmark to use to avoid skull base injury when beginning the superior septectomy. Methods: Preoperative computed tomography maxillofacial scans were reviewed from 100 patients from the University of Pennsylvania sinus surgery data base. The narrowest anteroposterior distance between the posterior edge of the NFB and the anterior aspect of the olfactory fossa (OF) at the level of the internal frontal ostium was measured in each patient. Measurements were taken in the midline and to the left and right of midline. Six fresh cadaver heads were also dissected to evaluate these relationships. Results: On computed tomography analysis, the NFB was anterior to the OF on the left and right of the midline in 100% of the patients, with mean distances of 6.04 and 6.41 mm, respectively. The NFB was anterior to the OF in the midline in 98% of patients, with a mean distance of 9.02 mm. In all six cadavers, the posterior edge of the NFB was anterior to the OF in the midline and to the left and right of midline at the level of the internal frontal ostia. Conclusions: During Draf III, the posterior edge of the NFB was a reliable landmark for avoiding iatrogenic CSF leak during the superior septectomy. [ABSTRACT FROM AUTHOR]

Background Meningiomas of the anterior skull base are attractive tumors for resection via an endoscopic endonasal route. The use of the vascularized Hadad-Bassagasteguy nasoseptal flap has dramatically reduced the cerebrospinal fluid (CSF) leak rate—the veritable Achilles heel of this surgical approach. Benign meningiomas, however, can erode through the nasal mucosa—the very same mucosa that is used to reconstruct the anterior cranial fossa floor. The goal of this study was to describe the presence of meningioma invasion into the mucosa in patients who underwent endoscopic endonasal resection of ventral skull base meningiomas. The implications of this finding are discussed with respect to resection, reconstruction, and recurrence. Patients, Materials, and Methods This is a retrospective review of three patients who underwent endoscopic endonasal complete resection of ventral skull base meningiomas. Surgically excised tissues were processed for routine histopathological analysis. Results A complete resection of the bone, dura, and tumor was performed in all three cases. Both patients with visual deficits improved. The first patient to undergo endoscopic surgical resection developed a CSF leak, but the later two patients with larger tumors did not. Histopathological analysis demonstrated mucosal invasion by World Health Organization (WHO) grade I meningioma in two of the three cases. Conclusion Ventral anterior skull base meningiomas can invade through bone into the mucosa. Because the endoscopic endonasal resection of these meningiomas often requires the use of a vascularized nasoseptal flap to minimize CSF leak complications, it is possible that the nasoseptal flap itself may be compromised by tumor tissue. The creation of the nasoseptal flap should take the findings of this study into consideration to minimize late recurrence. [ABSTRACT FROM AUTHOR]