• Erik C Brown, Brandon Lucke-Wold, Justin S Cetas, Aclan Dogan, Sachin Gupta, Timothy E Hullar, Timothy L Smith, and Jeremy N Ciporen.
• Department of Neurological Surgery, Oregon Health & Science University, Portland, Oregon, USA.
• World Neurosurg. 2019 Feb 1; 122: e121-e129.

BackgroundCerebrospinal fluid rhinorrhea from a lateral skull base defect refractory to spontaneous healing and/or conservative management is most commonly managed via open surgery. Approach for repair is dictated by location of the defect, which may require surgical exploration. The final common pathway is the eustachian tube (ET). Endoscopic ET obliteration via endonasal and lateral approaches is under development. Whereas ET anatomy has been studied, surgical landmarks have not been previously described or quantified. We aimed to define surgical parameters of specific utility to endoscopic ET obliteration.MethodsA literature review was performed of known ET anatomic parameters. Next, using a combination of endoscopic and open techniques in cadavers, we cannulated the intact ET and dissected its posterior component to define the major curvature position of the ET, defined as the genu, and quantified the relative distances through the ET lumen. The genu was targeted as a major obstacle encountered when cannulating the ET from the nasopharynx.ResultsAmong 10 ETs, we found an average distance of 23 ± 5 mm from the nasopharynx to the ET genu, distance of 24 ± 3 mm from the genu to the anterior aspect of the tympanic membrane and total ET length of 47 ± 4 mm.ConclusionsAlthough membranous and petrous components of the ET are important to its function, the genu may be a more useful surgical landmark. Basic surgical parameters for endoscopic ET obliteration are defined.Copyright © 2018 Elsevier Inc. All rights reserved.

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