Mouth-eye linkage is a sequela of facial palsy, and its clinical manifestations include eye-mouth linkage (the affected side closes its eyes with the ipsilateral corner of the mouth upward and facial spasm) and mouth-eye linkage (involuntary eye closing movement on the affected side when smiling or chewing), which leads to strange facial expressions and often causes great pain to patients. The reason for the mouth-eye linkage is that there are often overlapping areas between various branches of the facial nerve, especially between the zygomatic and buccal branches of the facial nerve. When the facial nerve is severely injured, the growth direction of the regenerated nerve fibers deviates, and the number of fibers traveling to the main functional area decreases, while the nerve function in the overlapping area is enhanced, resulting in a linked nerve. Mouth-eye linkage treatment targets the linked nerve and includes both nerve paralysis treatment and nerve separation treatment. Nerve paralysis treatment: Botulinum toxin is injected locally to paralyze the linked nerve. The advantages are that it is minimally invasive, has no significant side effects, can be repeated, and the effect is immediate. The disadvantage is that the effect is not long-lasting and the recurrence rate is high. Nerve-splitting treatment: This is a surgical procedure to find and cut the linked nerve. The advantage is that the effect is long-lasting and the facial dynamics can be rebuilt at the same time. The disadvantage is that it requires a combination of trans-facial nerve grafting and is often performed in two stages.