The relationship of the facial nerve and first branchial cleft anomalies--embryologic considerations.

A Type II first cleft anomaly may lie superficial to, deep to, or between the branches of the facial nerve. The embryologic basis of this finding depends on the variable relationship between the migrating facial musculature, as it passes forward from the second branchial arch to the face, and the epithelial elements which persist in the region of fusion between the inferior portions of the mandibular and hyoid arches.