Positional relationship between lacrimal sac and skull base: implication of risk of cerebrospinal fluid leakage during dacryocystorhinostomy.

Cerebrospinal fluid (CSF) leakage is a rare but severe complication during dacryocystorhinostomy (DCR). Understanding the details of the anatomy of the lacrimal drainage system and skull base is essential to avoid this complication. We examined the positional relationship between the lacrimal sac and skull base using 16 cadavers (22 sides) and using computed tomographic images taken in 81 patients (81 sides). Consequently, the frontal sinus intervened between the lacrimal sac and skull base in 81.8-90.1% of cases. The lacrimal sac fundus and posterior lacrimal crest were far from the skull base/cribriform plate, and the skull base above the lacrimal sac was considerably thick. These results indicate that the risk of skull base injury and consequent CSF leakage during DCR is extremely low. However, surgeons should be cautious of this complication by indirect injury due to a twisting movement of a bone rongeur applied to the maxillary bone during creation of a bony window in patients with no interposition of the frontal and ethmoid sinuses between the lacrimal sac and skull base.