Facial Paralysis and Facial Nerve Palsy

Muscle Transplant

Tendon Transfer

Facial Reanimation

The most common cause of facial paralysis is trauma to the facial nerve (cranial nerve VII), both accidental and surgical.  Facial nerve paralysis can also be congenital or as a result of Bell's palsy, i.e. idiopathic facial paralysis.  In some cases of congenital paralysis, a trauma at birth can be the cause.  

Facial paralysis can be partial or complete with the history of injury and anatomy dictating the choice of treatment.  The surgical treatment of facial nerve injury can be divided into the following groups

• Facial nerve repair

• Facial nerve repair with nerve grafting

• Hypoglossal nerve transfer

• Local (regional) muscle transfer

  • Temporalis tendon transfer

  • Masseter Muscle Transfer

• Microvascular functional muscle transplantation 

The goal of  reanimation surgery for facial paralysis is to restore spontaneous animation and a balanced natural smile in patients with cranial nerve VII paralysis.  

Anatomy

The complex arrangement, balance and motion of the facial muscles produces human expression.  The muscles work to move the forehead, eyes, face, upper lip, mouth and lower lip.  The illustration below divides the face in half and shows some muscles on the right and others on the left to reduce the crowding that would be seen if all muscles were superimposed.  The facial nerve is pictured on one side, showing four major branches that are not labelled - the temporal, zygomatic, buccal and marginal mandibular from top to bottom.  Pictured also are the temporalis and mandible muscles, which strictly speaking are not muscles of facial expression, but muscles of mastication.  These are not supplied by the facial nerve, but by the trigeminal nerve.   Both the masseter and temporalis have been used for reconstruction in facial reanimation procedures as outlined later.  

Preoperative Assessment

A thorough history and physical examination are performed to determine:

• Duration of paralysis.

• Location of lesion. 

• Cause of Paralysis.  

• Degree of Paralysis.  

The patient with a facial paralysis is evaluated by observation in both the resting and active phases of facial expression, with attention paid to movement during speech, smiling, laughing and sometimes with ingesting food.  Facial muscle functions can be variably affected depending on the extent of facial nerve paralysis.  Paralysis of the facial nerve can affect the brow, eye, nose, mouth, lower lip - depending on the branches of the facial nerve affected (see illustration above).  The eyelids and eye closure as well as the blink reflex are examined.  If the patient is able to move the lips in a downward direction, depressor muscle function and platysma muscle function are present.  If hearing or taste  are affected or decreased tear production is present in the ipsilateral eye,  then facial nerve is injured in the intratemporal course where it give off branches involved in hearing and taste.

Surgical reconstruction depends on both the extent of the injury and the level of the injury.  Lesions involving transection of the facial nerve in the extratemporal course are repaired primarily if adequate nerve is present proximally and distally.  If proximal and distal nerve ends cannot be repaired,  but are present, then nerve grafting is performed.  If a proximal nerve stump is not present, then a nerve transfer from the hypoglossal nerve or a cross facial nerve graft can be considered.  If the time after injury is great, and the facial muscles have been dennervated for a long time, then local muslce transfers or a functional muscle transplantation can be an option.  Local muscle transfers (temporalis tendon transfer, masseter muscle transfer) are outlined on another page.  In functional muscle transplantation a branch of the opposite facial nerve is used together with a cross facial nerve graft to supply a motor to a muscle transplant on the affected side.  The gracillis muscle is typically utilized, although the serratus muscle can be used as well.  The procedure and the stages are explained in the gracillis transfer page.

The figure below shows the facial features at rest of a patient with facial paralysis.  The affected nasolabial fold can have less definition in a long standing case.  The eyes appear unaffected at rest.  During smiling, the face becomes assymetrical and no motor function is detected on the injured side in a complete injury.  The ability to pucker the lips and depress the lips when showing the lower teeth can be affected.