38 The Facial Reanimation: Multidisciplinary Approaches
Abstract
Facial palsy is a devastating condition that can cause aesthetic, functional, and psychological consequences to the patient. Functionally the most relevant defect is lack of corneal lubrication because of inability to close the eyelid or blink. Nevertheless, the loss of facial symmetry and expression have psychosocial devastating effects in the patients. Functional preservation of the facial nerve during removal of lesions in the cerebellar pontine angle has been an ongoing concern in skull base surgeons. In spite of the remarkable development in surgical techniques, facial paralysis is not an uncommon complication, up to 10% of patients undergoing removal of cerebellar pontine angle tumors present with direct injury to the nerve. Various reconstructive techniques have been described, but there is no consensus regarding their indication. The most widely used to date being the classical hypoglossal-facial nerve anastomosis. The aim of this article is to describe the indications for which each technique is used, their results and the ideal time when each one should be applied.
Keywords: facial nerve, facial palsy, hypoglossal-facial anastomosis, skull base
38.1 Introduction
Facial palsy is a relatively common condition that, in most cases, recovers spontaneously. However, each year, more than 127,000 new cases of irreversible facial palsy are diagnosed.1 , 2 The consequences of facial palsy are devastating: aesthetic, functional, and psychological, in addition to difficulties in ocular protection, swallowing, oral continence, and lack of facial expression, interfering with social life. Several reconstructive techniques have been described, but there is no agreement on which is the preferred treatment. Although the results offered by these techniques are not perfect, many of them provide a satisfying aesthetic and functional outcome, which favors the patient’s self-esteem, social life, and return to work.
38.2 Different Facial Nerve Reconstruction Techniques
In order to carry out the different facial reconstruction techniques, it is essential to have a vast anatomic knowledge of the region involved (Fig. 38.1).
Fig. 38.1Anatomy of the region. (a) Regional dissection leaving bone structures intact. (b) Dissection after cranial and spinal partial resection. Right lateral view. The skin, subcutaneous tissues, and part of the temporal bone have been removed to expose the CNs VII and XII. The auditory-mastoid polygon is useful to locate the CN XII immediately proximal to the parotid gland, especially when a preauricular approach is used for a classical CNs XII–VII anastomosis. CN, cranial nerve; EAC, external auditory canal; Ext. Car., external carotid; Int. Car., internal carotid; Int. Yug., internal yugular; VA, vertebral artery.
38.2.1 Direct Neurorrhaphy
When the facial nerve is severed by trauma or during surgery, immediate reconstruction must be considered; the most straightforward and efficient technique is direct neurorrhaphy. This technique allows the functional recovery of voluntary and involuntary facial movements. Depending on the site of the lesion, neurorrhaphy may be performed at the cerebellopontine angle, in the petrous part of the temporal bone, or extracranially. Sometimes it is necessary to interpose a nerve graft between the two stumps of the facial nerve to avoid tension at the connection site. The results of direct neurorrhaphy are superior compared to other techniques. The facial motor cortex, designed to move the mimicry muscles, reconnects with them, achieving an excellent aesthetic and functional result. This is true as long as the repair procedure is carried out as soon as the lesion is generated (if possible, in cases of an iatrogenic section during surgery) or, at most, a few months later.
In the case series published, direct neurorrhaphy is carried out in three different approaches; when there is no separation between the proximal and distal nerve stumps, a direct neurorrhaphy can be performed. This technique provides the best results. If the separation between stumps is smaller, a rerouting of the facial nerve could be done by drilling the temporal bone,3 , 4 , 5 allowing a direct neurorrhaphy without tension. If a significant part of the nerve is missing, and the proximal and distal nerve stumps do not meet, an interposition nerve graft must be placed to facilitate neural continuity.
All these procedures provide adequate symmetry, and facial tone can be restored, being indistinguishable to the healthy side in electroneurographic studies. Synkinesis, that is, the massive activation of uncontrolled facial movements, is a common consequence in these procedures and is more frequent when the disruption site is closer to nerve origin. However, the incidence and intensity of synkinesis increase with nerve grafts, which can appear up to 4 years after innervation and partially tarnish the good results.
In summary, whenever possible, a direct repair of the facial nerve should be attempted, and if possible, by direct neurorrhaphy without grafting.
Fig. 38.2Anastomosis of VII–XII with classical technique in a cadaveric specimen: (a) drawing; (b) skin incision; (c) the superficial planes have been dissected, exposing the parotid gland, the sternocleidomastoid muscle, and superficial vessels and nerves; (d) deep plane; CN VII and branches after wedge resection of the parotid gland; (e) deep plane; partial resection of the parotid gland; (f) the CNs XII–VII anastomosis has been carried out. The CN XII has been transferred in the search for the CN VII underneath the digastric muscle. CN, cranial nerve; ECM, esternocleidomastoid; Ext. Yug., external yugular; Gr. Au., great auricular; Int. Yug., internal yugular; M., muscle; N, nerve; V., vein.
38.2.2 Hypoglossal-Facial Nerve Neurorrhaphy
Neurotization is the procedure of choice when there is no proximal stump to work with, as in cerebellopontine angle tumors in which the facial nerve is accidentally sectioned at the level of its origin near the brainstem.
The most used technique in the literature for neurotization of the facial nerve is hypoglossal-facial nerve anastomosis. It involves the section of the hypoglossal nerve and the consequent hemitongue paralysis (Fig. 38.2).
The first case of hypoglossal-facial anastomosis in temporal bone osteomyelitis was attributed to Korte in 1903.6 This technique was later popularized based on its excellent results.
Rehabilitation should be done from the beginning, preferably in front of a mirror; after a while, it is possible to teach the cortical neurons of the tongue to move the facial musculature in a partially independent form. Also, a correct palpebral and buccal occlusion, a restoration of active and resting facial symmetry, and voluntary management of the hemiface muscles could be achieved. With proper rehabilitation, the conscious control of the voluntary muscles is re-established, although it is impossible to recover the involuntary gestures, like those of the emotions, since these are mediated by the motor nucleus of the facial nerve.
The success rate of this technique is 60 to 70%1,2; the other 30 to 40% presents mediocre results due to weak muscle contraction. Failure in the surgical technique is more common in patients with oncologically advanced diseases, postoperative radiotherapy in the area of the anastomosis, or with a time interval, from the installation of the facial lesion until its repair, longer than 1 year.7
The maximum time to perform the hypoglossal-facial anastomosis should not exceed beyond 18 months, although it should be done as soon as possible, preferably before 1 year. Intervals greater than those mentioned above are associated with significant atrophy of the mimicry muscles, which are histologically replaced with adipose tissue after a few years. No matter how accurate the reinnervation is, if facial atrophy is reached, an effective functional or cosmetic result is not possible. Although there are exceptional cases published in the literature of patients whose surgery was performed 2, 3, and even 10 years after facial paralysis with good results.8 , 9 , 10 The best way to guarantee good outcomes is early surgery. If there is certainty of complete nerve injury, the restoration procedure should not be deferred beyond a few weeks.
The main problem with this technique is its morbidity. The denervation of the hemitongue causes phonation and swallowing difficulties. Words with / d / or / r / are difficult to pronounce initially, but after adequate phoniatric rehabilitation, the disorder could be managed. On the other hand, swallowing, especially the moving of the bolus inside the mouth, is also affected immediately after the anastomosis, but the patient, in general, becomes accustomed and adapts to his or her new situation after a few days.
In the case of postoperative cerebellopontine angle tumor surgery with IX, X, and/or XI cranial nerves palsy, the hypoglossal-facial anastomosis is contraindicated. This is because it may result in a worsening of the pre-existing speech and phonatory symptomatology.
To decrease morbidity, modifications in the technique have been described, including the side-to-end anastomosis.11 These techniques ensure simpler and safer restoration of facial innervation, but the results are often unpredictable and unsatisfactory, with good tone at rest, but a weak contraction of the facial muscles.
All techniques that do not use the facial nerve for neurorrhaphy, such as hypoglossal-facial anastomosis, have the problem of not allowing involuntary activation of facial mimicry. Therefore, various gesticulations like smiling can be trained, but the involuntary bilateral symmetrical expression will not be achieved in response to an emotional stimulus (fear or joy). Synkinesis, when talking, chewing, or swallowing, is also frequent.
38.2.3 Alternatives to Classic Hypoglossal-Facial Neurorrhaphy
During the last 20 years, several techniques had been described; the common purpose is to minimize the morbidity generated by the entire section of the hypoglossal nerve. A healthy hypoglossal nerve contains approximately 10,000 axons (9,778 ± 1,516), a number considerably higher than the amount of axons in a healthy facial nerve, around 7,000 (7,228 ± 950), so, in theory, it would be sufficient to use only part of the hypoglossal nerve.12 , 13 Different methods of approximation were described, such as mobilization of the facial nerve or the interposition of nerve grafts, to achieve anastomosis without tension. A recently published anatomical study analyzed the different surgical options to evaluate the required nerve exposure and specify the different techniques.14
May et al15 described, for the first time, the nerve graft interposition technique between the facial nerve and a partial section of the hypoglossal nerve; after this intervention, only 3 of the 20 patients treated suffered from hemitongue atrophy. Cusimano and Sekhar16 used this technique and obtained similar results, as did Flores,17 who most recently described eight patients with satisfactory facial resuscitation and reduced tongue mobility.
Arai et al13 modified the procedure slightly. They sectioned a few centimeters of the hypoglossal nerve longitudinally to anastomose it to the facial nerve, thus avoiding the need for an interposed nerve graft. This last modification raises doubts about its results because it is known that, due to the plexiform orientation of the peripheral nerve fascicles, the longitudinal dissection hardly preserves axonal indemnity.
On the other hand, Sawamura and Abe10 and Atlas and Lowinger12 suggested an alternative, drilling and exposure of the facial nerve in the facial canal, which provides a few more centimeters of the facial nerve which could be sectioned and rotated to anastomose it with the hypoglossal nerve partially sectioned (Fig. 38.3). The authors achieved positive results in a series of cases similar to those of the classical hypoglossal-facial anastomosis but without causing significant tongue morbidity (Fig. 38.4). Recently, an extensive series was published that reproduced this initial satisfactory results.18 Currently, this procedure is considered the best option for facial nerve reconstruction, displacing the classic hypoglossal-facial anastomosis with a complete section of the hypoglossal nerve.
