|RALPH T. MANKTELOW, BA, MD, FRCSC|
|DIVISION OF PLASTIC SURGERY|
|TORONTO GENERAL HOSPITAL|
|PROFESSOR OF SURGERY, UNIVERSITY OF TORONTO|
|RONALD M. ZUKER MD, FRCSC, FACS, FAAP|
|DIVSION OF PLASTIC SURGERY|
|THE HOSPITAL FOR SICK CHILDREN|
|PROFESSOR OF SURGERY, UNIVERSITY OF TORONTO|
Unilateral facial paralysis can have major functional as well as aesthetic effects. It may be congenital or acquired later in life. Frequently it is caused by Bell's Palsy, acoustic neuroma and other tumors and may occur in all ages. With the lack of 7th nerve function the muscles of facial expression are weakened or paralysed and do not provide appropriate support and movement for the vital structures of the face. Consequently, there can be lack of eye closure with exposure of the cornea resulting in an uncomfortable eye and possible corneal ulceration. Lack of nasal support may result in obstructive breathing. Lack of support around the mouth affects speech and may result in drooling. When the person's face is at rest, the paralysed side droops and the mouth and nose are crooked. With smiling the paralysed side is pulled toward the normal side resulting in an increased deformity. The function most often missed is the ability to communicate with a pleasant smile.
There are many surgical procedures available to reconstruct the paralysed face. The selection and execution of the most appropriate procedures for an individual is important in attaining a good result. Surgery for the eyelids to provide adequate support and movement involves many different procedures. Thus, each patient must be evaluated individually and a specific plan for eyelid protection and movement created. The commonest procedures are static slings for the lower eyelid and gold weights for the upper lids. However, these procedures will not be effective in some situations and muscle transfer or other procedures may be required.
Normally the smile is controlled through the 7th nerve. In a unilateral paralysis of the 7th nerve, we can bring facial nerve function from the normal side across to the paralysed side by a nerve graft. This cross facial nerve graft is the first stage in the reconstruction. The cross facial nerve graft procedure utilizes a nerve from the leg which is not of any functional concern and leaves only a small area of numbness on the foot. It is connected to the normal facial nerve and then brought across through the upper lip to the weak or paralysed side. Very careful nerve repairs are done under high power magnification in order to ensure adequate innervation of this nerve graft. After about six months nerve fibres grow inside the graft which can be used to innervate the transplanted muscle.
Muscle transplantation is the second stage of the reconstruction. A section of the gracilis muscle from the thigh is transplanted to the face. The muscle is taken with its blood supply and its nerve supply. It is positioned in the face so as to provide support to the lower lip. This support improves symmetry at rest. When the muscle contracts it will elevate the lower lip and corner of the mouth, thus improving speech, especially sounds that require the lips to be placed together. Lastly, and perhaps most important, when the muscle contracts it will elevate the corner of the mouth and upper lip and create the appearance of a smile.
The beauty of utilizing the cross face nerve graft and the 7th nerve on the normal side is that the contraction of the muscle will be spontaneous with smiling. Control of the muscle movement comes from the 7th nerve nucleus in the brain on the normal side. Thus, the muscle when innervated will contract and elevate the corner of the mouth and upper lip, making a smile. It will not be normal but it certainly will improve the overall static and active appearance of the lips and cheeks.
The muscle transplant procedure is quite complex and there is no room for error. The muscle must be appropriately positioned and oriented in order to perform the function that is wanted. It must also be securely fixed to the tissues in the lips so that it will not drift. The muscle must have a blood supply and this is where the microvascular anastomoses come in. Very small blood vessels of 1-1.5 mm in diameter must be joined together under the operating microscope in a perfect fashion. One artery and one vein must be repaired so that a circulation will be established into the muscle. Re-establishing the circulation for the muscle is essential for its survival. Next, a very careful nerve repair must be carried out which will innervate the new muscle. The muscle's nerve is attached to the previously placed cross facial nerve graft which brings in 7th nerve function from the uninvolved side.
This combination of procedures, cross facial nerve graft followed by muscle transplantation, is the most effective way of dealing with a unilateral facial paralysis in an individual who is prepared to go through these two complex procedures and has the potential for innervating the muscle effectively. The nerve graft procedure is done through a facial incision on the normal side just in front of the ear. This incision heals extremely well, much like a 'face-lift' incision. There are small transverse incisions in the calf for the harvest of the nerve which are also quite well hidden. After a suitable time for the nerve to grow across the face, usually 6-9 months, the muscle transplant procedure is done. The facial incision in this procedure is also just in front of the ear, but on the paralysed side, with an extension below the jaw line and heals well. The incision in the thigh, where the muscle is accessed, however, usually becomes widened and thickened. However, as the incision is in the upper inner thigh is not readily apparent and covered with normal shorts. There is no loss of thigh function associated with removing a segment of this thigh muscle. We consider this to be the ideal reconstruction to provide facial animation for individuals with unilateral facial paralysis.
Following the muscle transplant procedure it takes 5-10 months for the muscle to begin functioning. Gradual strengthening and improvement in movement can be expected over the next year.
Appended to this website is a list of articles published by the surgeons that explain the procedure in detail and can be easily accessed for further information.