Transverse facial artery: Its role in blindness after cosmetic filler and botulinum toxin injections.

Masseter injections for cosmetic or pathological reasons are increasingly common, as are filler injections using dual or multiplane techniques in the lateral facial regions or for jawline contouring. The occurrence of blindness following these procedures often remains unexplained. This study aimed to determine the anatomical explanation for this debilitating complication by investigating the transverse facial artery and its relation to the masseter. For this purpose, we dissected 35 cheek specimens with latex injections and 10 specimens without latex. The external carotid artery was dissected up to its bifurcation into the maxillary and superficial temporal arteries. Results showed that the transverse facial artery arose from the superficial temporal or external carotid artery that runs between the zygomatic arch and the parotid duct. Three types of transverse facial arteries were observed: type I: a short artery that did not extend beyond the masseter muscle; type II: a transverse artery that ran to the nasolabial fold and anastomosed to the facial artery; and type III: a sizable transverse artery that substituted the hypoplastic facial artery, continued as the angular artery, and then anastomosed to the dorsal nasal artery. Knowledge of these three types of transverse facial arteries is a prerequisite to study the vascular territory. Type III provides an explanation for the occurrence of blindness after lateral face injections. We consequently define a line that runs from the tragus to the outer quarter of the upper lip as the risk area, while the safe zone is located on either side of this line.