Facial Paralysis

These are the other main causes of facial nerve paralysis. Acoustic neuroma is the most common type of brain tumour involved. It is a benign (non-cancerous) growth that occurs on the eight cranial nerve which lies adjacent to the facial nerve. The eight nerve carries hearing information and balance signals from the ear to the brain. Symptoms of an acoustic neuroma include hearing loss, tinnitus (perception of noise ringing in the ear) and vertigo (spinning sensation). A hearing test and MRI can establish the diagnosis and the tumour may require removal by a neurosurgeon. 

The facial nerve divides into branches as it passes through the parotid salivary gland which lies just in front of the ear. Some or all of the facial nerve branches can be involved by malignant (cancerous) tumours of the parotid gland and may need to be removed together to ensure tumour clearance. 

The treatment approach to facial paralysis in tumour cases depends on the findings during the operation. A conservative approach is prudent if the surgeon who performs the tumour removal feels that the nerve was saved during the operation. Patients will require eye care and sometimes temporary surgical procedures on a case-by-case basis. If the nerve was cut during the operation or if the facial palsy does not resolve, then a more active approach must be taken. 

If one or more facial nerve segments need to be removed, they can be reconstructed using nerve grafts  harvested from other areas of the body. This can be done either in the immediate setting (at the same time as the removal of the tumour) or as early as possible (within 3-6 months is preferable). 

The nerve grafts can be connected to the same side facial nerve, or if this is not available, to the healthy side facial nerve or to the nerve to the masseter muscle (one of the muscles for chewing). As nerves regenerate at a speed of 1mm/day, between 6-12 months may be required before the nerve reaches the muscle and is able to activate it again. Radiation therapy may slow the speed of nerve regeneration and affect the final muscle strength achieved. In addition, fibrosis of the surrounding tissues will result in a tightness and contracture.

If more than 18 months has elapsed from the time of onset of facial nerve paralysis, the facial muscles would usually have atrophied and spontaneous recovery cannot be expected. Replacement of muscle function using functional muscle transfer is the ideal solution to allow the patient to smile again.

A strip of fascia lata can be harvested from the thigh via a small incision. The fascia lata is a layer that covers the thigh muscles and is relatively strong. A piece of it can be used as a hammock to suspend the lip and angle of the mouth to more stable structures in the temple or upper cheek area. Although it is simple procedure that can be performed even under local anaesthesia injections, the position of the lip is fixed is a slightly elevated position. In other words, patients do not have a dynamic smile. In addition, the fascia lata stretches with time and recurrence of lip drooping can be expected. Tightening of the fascia lata can be repeated in a second operation.

Other techniques such as face lift cannot reanimate a smile. as they do not affect the facial muscles.  However they can be important adjuncts to improve the soft tissue drooping that also occurs in facial palsy. 

 The temporalis muscle is one of the muscles responsible for jaw movement. One can locate it by feeling the temple area while biting down. This muscle can be diverted for smiling, by stitching its end to the smiling muscles around the mouth. A smile can be produced immediately post-operation by biting down. However after going thru a post-operative rehabilitation program, a smile can be produced without conscious thought as early as few months after operation. Functional MRI has shown that the brain adapts by the process of cortical plasticity such that it recognises the temporalis muscle as a “smiling muscle” instead of one for chewing.

When the facial muscles are in an atrophied state or are absent, muscle can be transferred from other parts of the body such as the back (Latissimus dorsi muscle) and thigh (Gracilis muscle) to replace them. After harvesting the muscle, there is no loss of function in the donor site as the body is designed with more than one muscle for the same job. The muscle is taken with its blood supply (artery and veins) and connected to blood vessels in the head and neck using microsurgery. Microsurgery is the joining of blood vessels under a microscope. The muscle is also harvested with its nerve which is connected to a branch of the healthy side facial nerve. After the nerve regenerates from the healthy side over a period 4-9 months, patients can smile as per normal without need for conscious activation. 

There are 17 muscles of facial expression on each half of the face. Smiling is just one of the functions of the face. For example restoration of brow position with brow lift techniques can reduce skin hooding that obscures vision and also improve appearance. This can be accomplished either by endoscopic techniques or by direct brow lift (which will leave a hairline scar above the brow). As eye closure can be impaired leading to dry eyes and tearing, definitive eyelid reconstruction such as with levator recession or gold/platinum weight may be needed. The lower eyelid can be tightened with techniques such as limited tarsorraphy, canthopexy/canthoplasty or inferior retractor recession. Assessment by our plastic surgeon specialising in facial nerve conditions is necessary to determine which techniques are most suitable in each individual case.