Anomalously coursing facial nerves above and below the oval window: three case reports.

Anomalous coursing of a dehiscent horizontal segment of the facial nerve, overlying or running below the oval window, is a rare phenomenon exclusively associated with conductive deafness caused by developmental abnormalities of the stapes and occasionally coincident with additional types of congenital auricular and nonauricular abnormalities. This article describes three new cases of this entity, including one previously unreported coincidence of an abnormally contracted tympanic ring, which should serve to alert the surgeon to the danger of surgical damage to a dehiscent, displaced facial nerve.