Chapter 61: The surgical treatment of facial paralysis
- A somewhat rapid reading on the subject of surgical treatment of facial paralysis revealed that the aim of surgeons appears to be three-fold (1) to protect the eye from exposure keratitis and to restore the ability to close the eye if not to restore the autonomous blinking reflex (2) to restore a symmetrical face in repose and (3) to enable the patient to smile. It was doubtful, from the available literature that was studied, when this chapter was written, if the other muscles of the face barring those attached to or near the angle of the mouth from above which help to create a smile, can be reanimated as effectively. For example, the crinkling of the eyes which normally accompanies a smile is probably not restored fully by surgery. A general appraisal of the literature also revealed that expressions such as “disapproval” usually shown by turning the angle of the mouth downwards, may not be possible to be reanimated by surgical treatment.
- That drew the attention of the compiler of these short notes to the subject of facial expressions in general and the expression of emotions in particular and the logical question that followed was, are facial muscles voluntary or involuntary? After all, emotions flash across the face almost instantly following an event, allowing little time for the individual to mount an effort to show a particular response. This question
when posed to many a senior clinician almost uniformly revealed that most of them had not really addressed this question during their clinical years though there is a hint of an answer to that question in Gray’s anatomy where it is mentioned that the motor nucleus of the facial nerve receives afferent fibres from the trigeminal ganglion, the trigeminal nerve being the predominant sensory nerve of the face. A conclusion can therefore be drawn that some instant reflex actions such as blinking which involves both the relaxation of the elevator of the upper eyelid as well as the contraction of the orbicularis oculi, to ward off dust are in fact involuntary by way of this trigeminal-facial confluence. That same ever reliable Gray’s anatomy in the preamble to the section on facial musculature also addresses the question on the spontaneity of facial expressions (Susan Standring Editor in chief and also the sectional editor on the subject, Elsevier 2008). Please also see Charles Bell, “Essays on the Anatomy and Philosophy of Expression. 2nd ed. London, Murray 1824.” See Loudon BMJ Vol 285 Dec.1982, as suggested by our international editor ACH Watson (see paragraph 11).
- In the lower animals, particularly the mammals, the cranium is small and the face and the sense organs are relatively large and project forwards and the facial muscles are mainly used to close or open orifices. This situation has changed as evolution has progressed. The cranium grew, the face came to be set back and over millions of years the facial muscles in the human race seem to have developed distinctively and are probably ‘inaccurately’(?) believed to have developed as muscles of expressions because in the absence of a proper membranous fascia they come to be attached to the skin directly from their bony origin and their actions are now culturally construed as facial expressions.
- Notwithstanding the above, as discussed earlier it is beyond any doubt that the face mirrors what goes on in the mind, sometimes almost instantly after the event that comes to happen in our physical or psychological environment in a purely involuntary manner. On the other hand our face has also been cultivated(!) to express various emotions in a voluntary fashion. This is called “acting”.
In the play Henry the sixth by Shakespeare, the king (Henry) utters the following words. “why, I can smile and murder, whiles I smile and cry ‘content’! to that which grieves my heart and wet my cheeks with artificial tears and frame my face for all occasions”. This duality of spontaneous emotions as also when they are enacted by design is a trait which is evident only in the human race and is almost entirely absent in the lower animals including the mammals. The elephants are known to gather around a dying fellow creature to mourn and their expressions and movements on that occasion can be perceived to be sombre by their keeper and those expressions are natural and genuine. Dog lovers will tell you that their dogs are capable of showing a variety of emotions, mainly aggression as well as displeasure and even sorrow but they are not as precise or sophisticated as in the humans and animals can not act as we do. We on the other hand can attend a funeral as a custom and assume a grave expression without actually feeling sad. Shakespeare in fact in his play Hamlet has these words in the mouth of the villain, Claudius who has killed his own brother to usurp his kingdom “with an auspicious and a dropping eye” to indicate his mixed feelings as he proceeds to marry his late brother’s wife even before “the funeral feast has gone cold”. This Shakespearean expression in fact derives from an older Scottish proverb about a false man who “looks up with one eye and down with the other”.
- All in all, the facial nerve serves complex functions by way of its connections to the motor cortex the basal ganglia and the brain stem, one of which is its secreto-motor function (salivary glands). The plastic surgeon is rarely called upon to restore this function. In fact, as explained in the subsequent paragraphs most of the treatment expected from the plastic surgeon involves treating the pathological effects on the nerve in its infra temporal portion.
- Leaving aside the evolutionary mystery of the development of facial expressions the surgeon is faced with a formidable problem when called upon to correct the effects produced by a paralysis of the facial nerve because ideally the surgical procedure would be expected to restore the whole gamut of expressions which appears almost impossible to achieve at present. In a recent study from Glasgow as revealed on the google search engine there are a total of forty-two muscles in the face which participate in creating a variety of expressions. At least one of these is supplied by the trigeminal nerve for example the masseter used for clenching teeth but a majority of the rest are supplied by the facial nerve and to re-enervate them individually or in groups is extremely difficult and therefore the results of surgery in this field have been somewhat fruitful but leave a lot to be desired.
- Luckily the distal innervation of the muscles in the middle two thirds of the face is marked by multiple inter connections. This means any injury in the distal part of the nerve is likely to be compensated by these inter connections resulting in little or no after effects. What is even more crucial is some of these inter connections will allow some of these distal branches to be used as innervators to supply affected nerves elsewhere, mainly on the opposite side via a cable graft without affecting the function on the unaffected donor side. This is easier said than done but Surgeons have however persisted with their efforts to improve their results with this method all over the world and Gautam Biswas from Kolkata in India is one of them. Formerly a professor of plastic surgery at the post graduate institute in Chandigarh this chapter is written under his generous guidance. He has also supplied, amongst others, several illustrations for the chapter. Dr. Gautam Biswas also pertinently noted, as this chapter came to be written, that the temporal and the mandibular branches of the facial nerve, at its two ends, have fewer or no inter connections and therefore restoration of function in this area is that much more difficult.
- The effects of paralysis of the facial nerve extend from the platysma in front to the occipitalis at the back which too is supplied by the facial nerve. But the effects are more pronounced in the face proper. The ability to furrow the forehead is lost and when the condition is unilateral an observer is able to notice the difference and may relook at the person’s face, a gesture that does not escape the attention of the affected person. Because of the paralysis of the frontalis the eyebrow tends to droop, may hang down like a curtain and in the elderly will add to the existing brow ptosis, enough to obscure vision (brow ptosis). This subject has been dealt with in an earlier chapter (chapter 31). In that chapter only age related brow ptosis has been dealt with. However an analysis of the literature on brow ptosis following facial paralysis reveals that the same surgical procedures as in the cases of senile brow ptosis are used in cases following facial paralysis and the re-neurotisation procedures used for the other muscles of the face which are described in the paragraphs that follow are rarely used to restore the action of the frontalis. The reader is therefore requested to refer to the chapter on brow ptosis in this blog for guidance (chapter 31).
- The paralysis of the orbicularis oculi increases the size of the orbital fissure and though the protection of the orbital contents is also the function of the levator palpabre superioris the conjoint action of the two muscles is missing. The absence of effective blinking means the pump like action of the orbicularis which drives tears from the lateral to the medial side and which also helps to drain the lachrymal sac is missing, causing tears to accumulate and also overflow (epiphora) because the punctum on the lower lid which drains the tears via the naso-lachrymal duct might be everted due to the laxity of the orbicularis of the lower lid and it cannot collect the lachrymal fluid effectively. This abnormal and ineffective circulation of the tears results in the failure of lubrication of the surface of the cornea causing irritation leading to further lachrymation but to no avail leading to more epiphora and with the eye unable to blink or close effectively the cornea remains exposed, the sclera turns red due to irritation, may be painful and the eye is very vulnerable to corneal ulceration a very significant indication for preventive surgery. Equally significant is the vacant look in the eye devoid of any expression.
Photograph courtesy Gautam Biswas
- The changes around the mouth are also easily visible even on a cursory glance. In repose, the corresponding angle of the mouth droops, as compared to its opposite member and when the person is asked to smile the comparison between the two sides of the face is glaringly obvious. The most remarkable attribute of the human face is its ability to smile. What is seen in cases of unilateral facial palsy is a pitiable asymmetrical expression, about which the patient is usually aware and when it is coupled with a vacant looking open eye it is enough to move even a seasoned plastic surgeon. (The only other facial deformity which evokes similar pity is acid burns of the face. There too the problem is not so much the scarring but of the obliteration of all expressions). This lack of expression in cases of facial nerve paralysis is perhaps the most crippling assault on the patients self-image and this therefore has been the subject of most of the efforts undertaken by surgeons. The paralysis of the orbicularis oris also affects swallowing and the food tends to get retained in the buccal sulcus due to the failure of the action of the buccinator .The speech might be affected because the bilabial sounds such as “b” or “p” cannot be produced properly and drinking fluids becomes difficult because the lips cannot be pursed leading to spilling of fluids which is hugely embarrassing to the patient. In addition, the small muscles of the nose which control the external nasal airway when paralyzed may lead to passive obstruction and result in wheezing. As mentioned earlier the patients self-image is what bothers the patient most because he or she feels extremely self-conscious during social interactions and then seeks the help of a plastic surgeon.
- The commonest form of facial nerve paralysis goes by the name of Bell’s palsy after
Charles Bell, Scottish surgeon from Edinburgh who first described it in the year 1821. This condition is almost always unilateral, has a sudden onset, is self-limiting and disappears in a matter of weeks or months. Considered viral in origin, for lack of any other known aetiology, it has been empirically treated with Prednisolone since the discovery of that drug. The diagnosis of the condition is made by a process of elimination in which possible intra-cranial and extra-cranial causes along the route of the facial nerve are ruled out by clinical examination and x-rays including a M.R.I if required.
- The second most common cause of facial paralysis is central, that is a cerebrovascular stroke in which the muscles of the upper part of the face are spared because the part of the facial nucleus which supplies this area has both an ipsi- and contralateral supply from the motor cortex. The frontalis muscle therefore is invariably spared but the literature is not quite clear as to if the orbicularis oculi is spared as well. An enquiry with several plastic surgeons revealed that none of them were ever called upon to treat such patients surgically to prevent damage to the eye because of exposure. A random enquiry with more than one neuro-physician revealed that the closure of the eye is almost always satisfactory and therefore treatment for the eye is rarely ever required (tarsorrhaphy a possible surgical solution in the elderly is included in a case report towards the end of the chapter though it was done on a younger patient). This is somewhat corroborated indirectly by cases of congenital uni- or bilateral facial paralysis in which corneal ulceration is rarely observed. The latter condition is named after Mobius who recognized and described it (German neurophysician of the late twentieth and early twenty first century).
Photographs courtesy Nitin Mokal and Ravin Thatte
- As for the rest of the face particularly in cases of strokes in the elderly a recovery in the mild form of strokes is not uncommon and includes recovery of lower facial muscles as well. In the more severe forms of strokes or following excisions of neoplasms in the brain many of which are malignant, the agenda for rehabilitation (including radiotherapy) is too rigorous for the patient to ask and receive surgical treatment for the paralysis of the facial muscles. The one exception perhaps might be when the patient experiences excessive drooling because of an incompetent oral sphincter or when the bolus of food stagnates in buccal sulcus due to the paralysis of the buccinator. As is also well known to most clinicians the results of most surgeries that aim to restore neuro-regenerative processes have poorer results in the elderly as compared to the general population and therefore procedures for drooling are usually static in nature by way of a static sling of a strip of fascia, a subject covered in a later part of this chapter. From what is gathered from literature there appears to be no specific operation described for accumulation of food in the buccal sulcus (particularly for the elderly) following strokes and manual removal by self or through ‘health care givers’ has to be relied upon for this purpose.
- An exception would be a younger patient who is otherwise healthy and whose cerebral stroke was caused because of, for example, a vascular anomaly which has been treated effectively and the patient is expected to have a normal life there-after. In fact surgery for reanimation of the face would seem to be reserved for patients generally below fifty five to sixty years in whom facial nerve paralysis has followed trauma for example fractures at the base of the skull, tumours such as acoustic neurinomas in which the facial nerve had to be sacrificed or when the nerve is damaged in those infective conditions of the ear where the facial nerve is irretrievably damaged but the infective pathology which caused the damage is now treated and contained.
- A plastic surgeon might also be involved in the treatment of facial trauma, particularly deep lacerations in which injuries to branches of the facial nerve can be seen when magnification is used which ought to be now a routine. In such cases the cut ends of the nerves are rarely ever separated and are best repaired immediately with suitable suture material and steps are taken post-operatively to maintain the tone of the involved muscles by means of local heat, electrical stimulation and local massage. This triad is used in all cases of paralysis of the facial muscles prior to any surgical method used to reanimate them. In cases involving malignant tumours of the face for example those of the parotid in which the facial muscles are spared but a part of the facial nerve is sacrificed, sural nerve grafts can be used to bridge the sacrificed branches of the facial nerve as far back as at the stylo-mastoid foramen.
- Some branches of the facial nerve are occasionally damaged in operations such as a face lift, excision of the sub-mandibular salivary gland or open fixations of fractures of the mandible. The mandibular branch of the facial nerve runs along the lower border of the mandible or occasionally up-to one centimeter below it and is best avoided by taking care while incising the skin or when the dissection is deepened. Similarly the temporal branch runs roughly from the lobule of the ear to one and a half centimeter lateral to the lateral border of the eyebrow and is particularly prone to injury in face lifts because the skin flap here is quite thin and the nerve has a comparatively superficial course. More often than not the injuries are in the nature of neuropraxia and this subject has been touched upon in the chapter on face lift. However if the injury is diagnosed as neurotemesis by electro-physiologic investigations then exploration followed by repair is performed as early as possible.
- The anatomy of the muscles of the face has been given in some detail in this blog in the chapter on face lift (chapter 50) and the anatomy of the facial nerve in the chapter on the surgical treatment of parotid tumours (chapter 40).What follows here are treatment options and the relevant diagrams and clinical photographs in cases of patients with facial paralysis.
- In the main, surgery for reanimation of facial muscles, like muscles in other parts of the body can be undertaken in a roughly stipulated time of between six months and one year (eighteen months at the most) provided the muscles are prevented from wasting and atrophy by way of electrical stimulation, some form of local heat and mechanical stimulation by way of a gentle massage, as already mentioned but this bears repetition. Under these somewhat ideal conditions the reanimation of muscles is usually achieved by re-innervation of the affected facial nerve or of its branches now lying fallow by bringing, neuro electrical impulses from another source. Currently the ideal though somewhat laborious method is to use only some of the corresponding (not all) filaments of the facial nerve branches from the opposite normal side as the efferent conduits. These filaments are joined to the finely dissected fascicles of a sural nerve graft at its donor end. The rest of the sural nerve graft (of an adequate length) is tunnelled across the upper lip to lie across on the affected side of the face and joined to the affected branches on the paralysed side. Experience shows that the use of some filamentous branches of the facial nerve of the opposite normal side do not adversely affect the function of the muscles on that side because of the numerous inter connections mentioned earlier. What is more the cross-face transfer is considered the most natural because the transfer involves identical neuro myotomes on the contralateral side.
Alternatively, when the bed is hostile with considerable scar, a vascularised nerve graft is used for the purpose of neurotisation.
All above photographs courtesy Gautam Biswas
- A somewhat older yet frequently used method is to reinnervate the affected facial nerve or its main branches by another normal nerve from the paralyzed side of the face. In the past the accessory, the hypoglossal or the phrenic nerve were used quite frequently but are almost given up now except perhaps a part of the hypoglossal nerve because of the consequences that followed to the function of the tongue, the shoulder girdle or the diaphragm. The motor branch of the trigeminal nerve supplying the masseter muscle is perhaps now the only commonly used re-inerveter because it lies in the same area, is easy to reroute and is thick enough to be split into fascicles to re-innervete more than one branch of the facial nerve. The results of this procedure have been found to be satisfactory though some loss of masseter function is a drawback of this method.
- The purists who would ultimately want to restore facial nerve function by cross face facial nerve anastomosis by way of a sural nerve graft sometimes use the rerouting of the nerve to the masseter as a preparatory procedure by joining it to the affected facial nerve or its branches. This ensures the best possible care of the denervated facial muscles by way of natural neuro-electrical stimulation. When the final cross face anastomosis is performed, the nerve to the masseter is restored by re-suturing its two cut ends. As an alternative, the sural nerve fascicles are joined to the recipient nerves by an end to side anastomosis to the nerve to the masseter yet keeping the original end to end anastomosis of the nerve intact. Occasionally the reinnervation of the orbicularis oculi by the filaments of the masseteric nerve is retained and only that part of the nerve used to reanimate the elevators of the lip is restored to its original course and the cross face sural nerve graft is employed for reanimation of the muscles attached to the angle of the mouth for a smile.
- A part of the masseter muscle has also been used as a transfer to the angle of the mouth from above to recreate a smile but this will require training in which the patient is asked to clench the teeth to usher in a smile. This flap of the muscle is only a partial harvest based superiorly and includes the anterior half of the muscle. This arrangement is convenient because the nerve to the masseter a branch of the mandibular division of the trigeminal nerve as well as the blood supply to the masseter enter the muscle near the superior base of this flap from above under the zygomatic arch.
- The masseter can also be developed as a double flap the medial one being used to reanimate the orbicularis oculi in an anti-clockwise arc and the middle part of the masseter used to lift the angle of the mouth to create a smile. These procedures will require some training on the part of the patient in which the patient must undertake a clenching action of the teeth to effect the desired result.
- The other muscle which is frequently used for the purpose of reanimation of the face is the temporalis muscle which is also supplied by the trigeminal nerve. The temporalis can be used both for the eye as well as the mouth. The standard technique is to raise a flap from the central or anterior third of the muscle in a vertical fashion, based inferiorly, ensuring that both the blood supply as well as the nerve supply remains intact. The nerve to the temporalis is also a branch of the mandibular division of the trigeminal nerve and enters it from below. The blood supply of the muscle enters the muscle from its deeper surface by way of the deep temporal artery a branch of the maxillary artery from below and the flap is raised deep enough over the bony temporal fossa to include the vessel. The flap is then turned over and used together with free grafts of fascia as extensions to go around the eyelids and is anchored to the medial canthal ligament. In the case of the angle of the mouth the fascial extensions first pull the angle up, to make it symmetrical to the opposite side by anchoring it to the confluence of the orbicularis oculi or the modulus . The modulus is an important part of the anatomy here. At rest the muscle tone (elevators and depressors) balances this modulus. Expressions reflecting emotions are mainly mirrored by the movement of the same modulus. This requires adjustment of a certain tension which at best is empirical because the patient is invariably under general anaesthesia. The fascial extensions mentioned above can be harvested from the fascia overlying the temporalis muscle or are left attached to the upper end of the flap and turned around as extensions. This reanimation is not in the same class as in the cross face nerve restoration because it is (in a way) indirect and requires some training on the part of the patient but the procedure is easier to do and has been found to be adequate in the long run for the average plastic surgeon. If the masseter is used for the angle of the mouth and the temporalis for the eye, the retraining of the patient is easier.
Illutrations photoshopped from Plastic surgery editor Peter Neligan Elsevier 1990
- Nitin Mokal a cranio-facial surgeon from Mumbai India describes a modification in the use of the temporalis muscle and rightly mentions that the use of the temporalis when it is relocated leaves behind a discernible defect in the temporal region which cannot always be hidden even when hair is used to camouflage the defect. In this modification in the use of the temporalis muscle its anterior two thirds is left in situ after it is separated from the rest of the muscle and is dissected up-to its tendon which is attached to the coronoid process of the mandible. This tendon is then detached from that process. A facial graft is then sutured to this tendon and is then tunnelled under the skin and withdrawn at the angle of the mouth by a small incision, to allow it to be sutured to the modulus of the orbicularis. This fascial graft is then split along its length in its lower half tunnelled under the skin of the upper as well as the lower lip to be sutured to the orbicularis muscle, even beyond the midline.
Photographs courtesy Nitin Mokal
- The idea and later the practical application of a free neurovascular transfer of a muscle to the face has been around for many years. As an example in a case of post traumatic facial paralysis in which the proximal trunk of the facial nerve is intact but the patient has come late for treatment and all the muscles of facial expression are irreversibly wasted the idea of bringing a live muscle to the area with its nerve and then to neurotise it through the existing facial nerve is extremely attractive. A free muscle transfer has also been used together with cross face nerve transfer in cases in which a facial nerve remnant is not available for example in cases of severe trauma and the affected muscles on the paralyzed side are already wasted. Once the axonal regeneration in the sural nerve is established as proved by a positive Tinels sign a free neuro vascular muscle flap (usually the gracilis) is transferred to the face and is neurotised by way of these sural nerve cable grafts to a branch of the obturator nerve which supplies the gracilis and the muscle’s distal musculo-tendinous strands are attached to the facial muscles mainly the elevators of the angle of the mouth for a smile as well as the orbicularis oculi to enable the eye to be closed. By a general consensus the gracilis muscle is considered to be the most suitable for the purpose of reanimation of the face because it is slender, has a long neuro-vascular pedicle and can be harvested simultaneously when the face is being exposed (please see chapter 58). A free neuro vascular muscle flap can also be neurotised with the help of the nerve to the masseter which will avoid the labour involved in the procedure of cross facial nerve anastomosis.
Photo-shopped version of an original diagram in the chapter on facial palsy
Photographs courtesy Samir Kumta.
- The surgical treatment for the effects of facial nerve paralysis began with what are now called static methods. A lateral tarsorhaphy to reduce the size of the orbital fissure is still practiced in the elderly to protect the eye ball and to prevent corneal ulceration as well as to reduce epiphora by reversing somewhat the ectropion of the paralyzed lower lid. Similarly the upper eyelid can be weighed down to create a mild ptosis by using a gold plate which is placed in a plane deep to the orbicularis muscle and attached to the upper border of the tarsus. This procedure is still in vogue today because gold as an implant is not reactive (a platinum implant is also used) is weighty as compared to the light implantable materials that have been discovered in the recent past. The gold implant prior to its use is placed on the eyelid to gauge its effect in lowering the eyelid and is customised for each patient. There is however a small percentage of cases in which the implant might get exposed. Recently free fat grafting has been attempted by Nitin Mokal and has some merit for the ease with which it can be done and should some absorption occur the procedure can be repeated.
- A procedure to achieve symmetry between the two angles of the mouth while in repose, which uses a fascial sling attached below to the area around the orbicularis modulus and fixed above to the zygomatic arch was perhaps one of the earliest operations for a facial palsy. Such a procedure can be done for the lower eyelid alone with the help of a fascial sling shown below.
These procedures have their own limitations, being static but serve a certain purpose. These procedures have also been combined with a face lift. Recently after the description of SMAS, a subcutaneous aponeurotic layer in the face, a face lift combined with plication of this layer together with a fascial sling has also been employed to give some relief to the patients when they come late. This however at best a palliative procedure. The face lift can also be performed with the help of artificial threads.
A set of photographs of patients in whom a combination of methods mentioned above have been used are reproduced below.
Photographs courtesy Nitin Mokal
- In fact notwithstanding the technical advances made in this field the results of the procedures narrated in this chapter are not universally satisfactory, certainly not in those cases which come late for treatment. Counselling these patients preoperatively over `more than one session is therefore of utmost importance lest a patient receive an additional psychological setback on account of unsatisfactory results to what has already been endured. Generally speaking though a surgeon might be attempting to restore emotions to a paralysed face what he achieves is probably some restoration of motions.