Facial Reanmiation

dynamic Facial reanimation

Facial reanimation is the reconstruction of a dynamic smile. The goal is to create a mimetic, natural smile initiated by emotion.

In unilateral facial palsy we use the signals created by the opposite, functioning facial nerve to initiate movement. The electrical signal is carried across the face by a nerve graft to the paralysed side to power a new muscle in the cheek. In effect, when the ‘good’ side smiles, the paralysed side moves as well. This can create a smile in response to emotion. In cases when there is a loss of adequate eye closure it is also possible to transfer a muscle to the eye to re-create a natural blink. This requires an additional nerve graft to carry the signals from around the functional eye and transfer of the very thin platymsa muscle from the neck.

In bilateral facial palsy there is no facial nerve available to power the muscles and we have to rely on an alternative nerve to make the new muscles move. Most often this is a ‘biting’ nerve and the patient has to learn how to use the chewing action to create movement. This means that the smile in response to emotion is difficult to create and is only seen when the reconstruction is performed in young children whose brain is able to re-learn.

unilateral reanimation

The gold standard of unilateral facial reanimation is the two-stage reconstruction.

In stage one a nerve graft is harvested from the lower leg (sural nerve) through a series of small incisions along the lateral ankle and up the lower leg. This nerve normally provides sensation to the lateral aspect of the foot and removing it will leave a small area that has reduced sensation thereafter. Then the skin of the normal non-paralysed cheek is raised in a similar fashion to an aesthetic facelift, although the incision is carried down onto the neck. This provides access to the normal facial nerve branches where they innervate the muscles of the face. Nerve stimulation is used to select a branch that causes a smile in the mid-face and this is sutured to one end of the nerve graft. The nerve graft is tunnelled across the face and the ‘free’ end left under the skin, next to the ear on the paralysed side. The muscles of the face are innervated by lots of branches of the facial nerve and using one to power the graft does not cause any loss of smile on the normal side.

The nerve then grows along the nerve graft. This is a slow process and takes 6-9 months to reach the other side at which point the patient can move to stage two: the muscle transfer. This involves a similar incision on the paralysed side of the face. The facial artery and vein are identified and these will be used to keep the muscle alive. There are several choices of muscle that have been described, typically the pectoralis minor from the armpit, or the gracilis from the inner thigh. Mr Woollard prefers the pectoralis minor. This is a thin, pliable, fan-shaped muscle that is the best replacement for the lost muscles of the cheek. It is a more difficult muscle to harvest, which is why most centres offer the gracilis. However, the gracilis is a tube-shaped muscle and this is much more bulky in the cheek afterwards and tends to create a ‘bridling’ effect as it contracts. The incision for the pectoralis minor is well hidden in the fold of the armpit and there is no loss of function once it is removed since the larger pectoralis major more than compensates.

After the surgery there is a delay as the nerve reinnervates the muscle which can take 6-12 months. Initially the muscle starts with uncoordinated twitching, but with intensive physiotherapy and rehabilitation exercises this becomes more controlled and natural. There is a degree of uncertainty in the extent of reinnervation (this depends on the quality and number of nerve fibres in the donor nerve, how well they grow along the graft and how effectively they make new connections in the muscle) but 4 out of every 5 get some movement, and one of those 4 will get an excellent result. In one case out of five the muscle does not contract. In these cases the muscle will act as a static sling supporting the face even if it does not contribute to a dynamic smile.

In a case of congenital facial palsy stage one would ideally be performed at 4 years of age, and stage two before the age of 8. In cases of Bell’s palsy we would wait for up to 18 months to ensure all spontaneous recovery has ceased before assessing whether or not a reanimation procedure would be of benefit. In cases of traumatic or surgical injury it is often better to intervene sooner.

In some cases of adult paralysis it is possible to perform a functional muscle transfer in a single stage using a latissimus dorsi muscle from the back. In adults the nerve to this muscle is long enough to reach across the midface. The incision on the paralysed side, and in the armpit is very similar to the two-stage, however it requires an incision in the groove in the middle of the face (the nasolabial fold) on the non-paralysed side to access the functioning facial nerve.

bilateral reanimation

Bilateral paralysis is fortunately quite rare. Most reanimation procedures in bilateral or Moebius cases are performed when the patient is still a child, usually around the age of 8. Each case is unique, since many will have involvement of other cranial nerves or areas of the body and this can alter the available muscles and nerves to us in the reconstruction. The most common approach is to harvest a part of the latissimus dorsi muscle from the armpit on both sides and insert these muscles into the cheeks through facelift type incisions as described above. The facial arteries and veins are used to keep the muscles alive, in a similar fashion to a unilateral transfer, but the nerves are connected to ‘chewing’ nerves in the deeper muscles of the face.

Again, there is a delay as the nerves grow into the muscles and reinnervate them, followed by a period of uncoordinated activity that requires physiotherapy to develop control. The smiling action is not as natural as in a unilateral reanimation because it requires a bite to activate the muscle, however, since it is a bilateral movement it benefits from symmetry.

dynamic reanimation of the eye: blink

In cases where there is a loss of blink the surface of the eye can be at risk of injury or ulceration. This results in the cornea becoming cloudy and reduces visual acuity. There are a number of procedures for addressing issues with the eye (weights added to the upper lid to aid closure, tightening procedures to the lower lid to hold it in a better position, etc) but it is also possible to restore blink. This is a similar two-stage process as described above using an additonal nerve graft and muscle transfer. In this case the nerve selected on the non-paralysed side is one that innervates the orbicularis occuli. Often the additonal nerve graft is added at the same surgery as the primary first stage for reanimation of the midface. At the second stage the platymsa muscle is harvested from the neck on the non-paralysed side (by re-opening the incision used at the first stage) and inset into the upper and lower lid on the paralysed side. The blood supply is from the superficial temporal vessels which run in front of the ear, and the nerve graft from the opposite, functioning eye is used to innervate the muscle.