Morphometry and morphology of extracranial part of facial nerve - A cadaveric study

Identification of the extracranial part of facial nerve with respect to bony landmarks is important to avoid injury to it. Purpose: To measure the length of the facial nerve trunk and its divisions and to measure the distance of the nerve trunk with the mastoid process and atlas. The variations in the divisions and branches were also noted. Methods: Twenty hemi-faces were dissected. The facial nerve was identified at the stylomastoid foramen and dissected meticulously through the parotid gland. The divisions and branches were identified and traced. The trunk was measured from the stylomastoid foramen to its point of bifurcation. The length of the two divisions were measured up to their branching. The distance from the nerve trunk to the mastoid process and atlas were measured. Results: Mean length of facial nerve trunk in centimetres was 1.380±0.082, length of upper division was 0.820±0.108 and length of lower division was 0.890±0.090. The mean distance in centimetres between the facial nerve trunk and mastoid process tip was 1.300±0.089 and the distance between facial nerve trunk and transverse process of atlas was 1.645±0.108. Conclusion: The above data may help in minimising injury to the facial nerve.