An anatomical study on the distribution of the temporal branch of the facial nerve.

In an attempt to define the distribution of the temporal branch of the facial nerve, 30 facial halves of 15 Japanese cadavers were dissected. The tissue plane in which the temporal branch ran was investigated and the relationship between this nerve and the surrounding tissues observed. To quantify the distribution, the distance from the bony lateral canthus (LC) to the points where the temporal branches crossed two standard lines, (L1 and L2) were measured. These latter were determined according to the skeletal landmarks. The temporal branch consistently lay along the undersurface of the temporoparietal fascia. But its depth below the skin was not constant because the amount of overlying adipose tissue varied and it was localized within a limited area. The temporal branch generally branched into 3 or 4 rami and its trajectory was either straight or curved, depending on the relationship between the middle and the posterior ramus. The distances from LC to each point were relatively constant and there was no difference between the right and the left side. It is important for surgeons to know the quantified course of the temporal branches based on the skeletal landmarks. As a consequence of the quantification, it was possible to establish new guidelines for protection of the entire temporal branch from surgical injury.