The Nasofrontal Beak: A Consistent Landmark for Superior Septectomy during Draf III Drill Out

Abstract

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.