Anatomy of anterior ethmoidal foramen, medial canthal tendon, and lacrimal fossa for transcutaneous anterior ethmoidal nerve block in Japanese individuals.

Purpose: To examine the anatomical relationships of the anterior ethmoidal foramen (AEF), medial canthal tendon (MCT), and lacrimal fossa (LF) in Japanese individuals.

Methods: Thirty-eight orbits from 19 Japanese cadavers (7 men and 12 women; average age at death, 89.3 years) were used in this experimental anatomical study. The AEF, MCT, and superior border of the LF were exposed. The following distances were then measured: 1) from the point at the medial orbital rim directly anterior to the AEF to the superior border of the MCT (AEF-MCT), and 2) from the superior border of the LF to the superior border of the MCT (LF-MCT).

Results: (AEF-MCT) and (LF-MCT) distances were 9.40±1.92 (mean±standard deviation) and 4.21±1.18 mm, respectively. No values of (LF-MCT) exceeded the mean (AEF-MCT) (9.40 mm).

Conclusions: The transcutaneous anterior ethmoidal nerve block can be reliably performed without injury to the lacrimal sac by inserting a needle approximately 9 mm superior to the superior border of the MCT.