Relations of Facial Nerve With Retromandibular Vein in Human Fetuses

The relationship of facial nerve (FN) and its branches with the retromandibular vein (RMV) has been described in adults, whereas there is no data in the literature regarding this relationship in fetuses. The study was conducted to evaluate the anatomic relationships of these structures on 61 hemi-faces of fetuses with a mean age of 26.5 ± 4.9 weeks with no visible facial abnormalities. The FN trunk was identified at its emergence at the stylomastoid foramen. It was traced till its ramification within the parotid gland. In 46 sides, FN trunk ramified before crossing RMV and ran lateral to it, while in 8 sides FN trunk ramified on the lateral aspect of the RMV. In 3 sides, FN trunk ramified after crossing the RMV at its medial aspect. In only 1 side, FN trunk trifurcated as superior, middle, and inferior divisions and RMV lied anterior to FN trunk, lateral to superior division, medial to middle and inferior divisions. In 2 sides, FN trunk bifurcated as superior and inferior divisions. Retromandibular vein was located anterior to FN trunk, medial to superior division, lateral to inferior division in both of them. In 1 side, RMV ran medial to almost all branches, except the cervical branch of FN. Variability in the relationship of FN and RMV in fetuses as presented in this study is thought to be crucial in surgical procedures particularly in early childhood.