Meet the Sac: Endoscopists’ Road Map

Abstract

Objectives: Ideal mucosal incision followed by adequate osteotomy is the key to successful endonasal endoscopic dacryocystorhinostomy. Hence anatomical correlation of intranasal lateral nasal wall landmarks to lacrimal sac and duct was done with secondary computed tomography (CT) correlation. Methods: A descriptive study of 10 adult cadaver head sections fixed with 10% formaldehyde solution was done in the anatomy and radiology departments of a tertiary hospital from 2010 to 2011. Following CT scan, these were sagittally sectioned to 10 right and left specimens. Measurement of anatomical landmarks in CT and dissection were taken by metric ruler and digital calipers respectively. With application of paired t test, mean was calculated. Results: Maxillary line was clearly identified in 75% of cadavers, the majority overlapping the lacrimal sac. In all cadavers superior end of lacrimal sac was above the axilla, distance between them being 8.88 mm. Length of lacrimal sac was 11.72 mm. These showed positive correlation with CT scan. Distance between anterior edge of lacrimal sac and axilla was 10.58 mm. Genu was at or posterior to nasolacrimal duct in the majority, the length of duct being 10.27 mm. This showed positive correlation with CT. Conclusions: Important endonasal landmarks are of middle turbinate—axilla and genu (bony), and maxillary line (mucosal). Mucosal Incision, 9 to 10 mm above axilla, anterior to maxillary line and genu, 10 to 11mm long to just above level of genu, is sufficient to expose lacrimal sac up to its inferior limit. Preoperative CT scan can be reserved for revision or post-traumatic nasolacrimal sac pathology.