Facial nerve: vascular-related anatomy at the stylomastoid foramen.

We dissected 30 facial nerves in fresh cadavers after arterial casting with red latex to provide specific information about the arterial-related anatomy of the trunk of the facial nerve from the stylomastoid foramen to its bifurcation. We found that a wide anatomic variability does exist. The trunk of the facial nerve was in proximity to the stylomastoid artery, which originated from the posterior auricular artery in 70% of the specimens (21/30), from the occipital artery in 20% (6/30), and directly from the external carotid artery in 10% (3/30). The stylomastoid artery passed medially to the trunk of the facial nerve in 63 of the specimens (19/30) and laterally in 37% (11/30). Among these 11 specimens, 8 were large-caliber stylomastoid arteries. During parotid surgery, the main trunk of the facial nerve may be difficult to identify, because a large-caliber stylomastoid artery can mask it. Therefore, it is important to dissect this artery with caution.