Course patterns of the marginal mandibular branch of the facial nerve
A segment-based model of a surgically vulnerable facial-nerve branch: its vertical position changes relative to the facial artery, its course may dip below the mandibular border, and its branching and communicating network make a fixed-distance “safe rule” unreliable.
Posterior to the facial artery is the variable—and vulnerable—segment.
One or more branches may descend below the inferior border of the mandible posterior to the facial artery, whereas anterior to the artery the nerve is almost always above the border. Safer access therefore depends on combined bony, vascular, fascial, and positional landmarks.
The position changes along the course
The review emphasises a segment-dependent rather than fixed-distance model of marginal mandibular anatomy.
Posterior segment
Older and pooled studies show that one or more branches may descend below the mandibular border posterior to the facial artery.
Anterior segment
Anterior to the facial artery, the nerve is almost always located above the inferior mandibular border.
Vessel crossing
The MMB usually crosses the facial artery and vein superficially, although deep and looping relations occur.
Three general trajectories
Select a pathway to see how the nerve behaves relative to the inferior mandibular border.
No single landmark is enough
The review argues against a universal 2 cm safe rule and favours a multimodal anatomical strategy.
Facial artery crossing
A practical landmark for locating the MMB at the mandibular border.
Inferior mandibular border
Useful, but not protective when used alone because low branches are common.
Fascial plane
Posterior subplatysmal dissection leaves a protective tissue bridge; anteriorly the nerve is more exposed in the platysma–SMAS plane.
Neck position
Extension may displace the nerve inferiorly and alter operative relationships.
The nerve is more connected than the classical model suggests
High-magnification studies reveal buccal–MMB and MMB–cervical communications far more frequently than standard dissection, helping explain partial deficits and spontaneous recovery.