Surgical anatomy of the singular nerve.

The course of the posterior ampullary (singular) nerve has been studied in 30 preserved human temporal bones. In 17 dissections (57%), the nerve was readily accessible in the floor of the round window niche without undue risk to the round window membrane or the ampulla of the posterior semicircular canal. In 5 bones (16%), the nerve was closely related to the round window membrane and could not have been approached without significant risk of damage to the membrane. In 8 (27%), the nerve ran more or less directly medially to the internal auditory meatus without entering the round window niche. The ampulla of the posterior semicircular canal would therefore have been at risk if the nerve were approached surgically.