Figure 1. Transverse multi-detector row CT scan of a normal left temporal bone. Tympanic membrane (1) runs laterally to the chorda tympani (2). Anterior (3) and posterior (4) crura of the stapes are shown. Canal of the accessory nerve of the posterior ampullary nerve (5) emerges from the posterior wall of the internal auditory canal laterally and leads to the canal of the posterior ampullary nerve (6). Within a distance of approximately 7 mm, both canals merge to one canal (7) leading directly to the posterior ampulla.