Anatomical consideration for dacryocystorhinostomy.

To understand better the regional anatomy of the bony nasal window in dacryocystorhinostomy (DCR), anatomical dissections were performed on 28 cadaver specimens with an average age of 80.1 years. The distance between the point which is located 10 mm posterior to the medial canthus and the anterior cranial fossa floor was measured. The distance ranged from 1 to 30 mm with an average of 8.3 mm. There was no difference between males and females. Six cadavers out of 28 (21.4%) showed 3 mm or less in the distance. When a chisel was inserted through the medial canthus, the tip appeared near the anterior cranial fossa floor in cases with a short distance and a small frontal sinus but not in cases with a long distance and a large frontal sinus. It is obvious that, if a posterior nasal window is enlarged more than 3 mm above the medial palpebral tendon, a bony opening will be formed in the anterior cranial fossa floor in these 6 cases, resulting in cerebrospinal fluid leakage. In conclusion DCR should be done without severing the medial palpebral tendon to make a bony nasal window under the tendon.