Congenital Facial Weakness
Each of us enters this world in a profoundly dramatic way. Either by unrelenting naturally propulsive physical forces through vaginal birth or abrupt, overwhelming surgical intervention, we are thrust into a radically different, startlingly harsh environment. Our first reaction, if we′ve successfully run the gauntlet, is to wave our arms and legs around in protest and shriek unmercifully. Hopefully at the other end there will await a highly skilled attendant, who will not only take care of our initial needs for comfort and warmth, but also catalogue our responses; count fingers and toes; note skin color, heart rate, and breathing; and meet our visible and audible objections with a warm reassuring gaze and loving smile. If all is in order, we will sooner or later smile, or more probably, contract all facial muscles in response, demonstrating normal function of our muscles of facial animation. Rarely, in those precious, very first moments of the outside world, we might not be able to return that simple gesture. Our attendant′s smile will then bleed into a look of consternation as the unmistakable presence of a congenital facial palsy will be recognized.
Fortunately, an event such as the one described happens only rarely, as the incidence of facial palsies at birth is between 1 and 2 for every 1,000 live births. A wide range of presentations are included in this finite cohort with only an extremely small fraction of those representing profound, complete facial nerve paralyses. An overwhelming majority of congenital facial palsies reported in the literature are associated with problematic labor or specific birth trauma, presumably associated with the use of forceps and most of those are transient.1 With the abandonment of this procedure in nearly all modern day obstetrical practices, we can expect that the overall rate of congenital facial nerve injuries has almost certainly decreased in kind. As with acquired forms of this disease, congenital palsies can present as unilateral or bilateral, complete or incomplete, transient or permanent.
Work-up
The initial work-up of a patient presenting with any degree of facial paralysis should begin immediately with a thorough cranial nerve examination highlighting careful observation and annotation of the presence or absence of function of all relevant cranial nerve innervated facial muscles. These involve not only muscles controlling facial expression but those responsible for ocular control, sphincter competency, chewing, and deglutition. While still photo documentation is required, video sequencing is critical for more reflective study of the specific deficiency and can be entered into standardizing databases that currently have the capacity to quantify deficiencies and more accurately track changes, thus helping guide long-term therapeutic decision making. Of course, early appreciation of facial palsy, in some cases, may lead to a more precise diagnosis. Important points to be noted should include any history of prolonged or otherwise difficult birth such as cephalopelvic disproportion, arrested descent, or protracted labor. Family history of facial paralysis either alone or with other deformities should raise suspicions of syndromic presentations. Any use of forceps should be documented and should lead the investigator to search for and make particular note of even the smallest signs of bruising, swelling, or deformation in the region of the temporomandibular joint area as well as hemotympanum in the ear canal.
Even in the newborn, identification of uni- or bilaterality as well as degree of completeness should be assessed as soon as possible. Initial component evaluation of upper, mid, and lower facial nerve function helps better define each particular defect.2 As follow-up evaluations are done, the precision and thoroughness of the initial assessment becomes crucial in measuring progress toward resolution and restoration of function or lack thereof. Of the several quantitative evaluation tools available, the most widely used and longest standing grading system to aid in categorizing severity is the House-Brackmann scale (see Table 5.2 in Chapter 5).3 The enduring nature of this device is (1) its simplicity of use, asking the observer to critique the face at rest, then in motion; and (2) its reliable correlate to eventual return of function. The severity of the condition is reflected in a higher score, grade I being normal, through to grade VI describing total facial paralysis. The Sunnybrook scale (see Table 5.5 in Chapter 5) is in common use as well. Ahrens et al have developed a downloadable program that allows observed data entered to be measured across multiple grading scales. 4
Unlike in the acquired varieties of facial paralysis, laboratory testing and analysis does not aid in the differential diagnosis in any substantive way with congenital facial paralysis. If there is either a history of similar problems in other family members or associated findings in the affected patient, genetic screening tools might be utilized to help characterize syndromic conditions. In the rare instances where chromosomal abnormalities are diagnosed, timely and appropriate genetic counseling may be appropriate.
Imaging studies, including plain skull series, computed tomography scanning, and/or magnetic resonance imaging, do not have a substantial role in the diagnosis and treatment of congenital facial paralysis. The one exception is in those positively diagnosed cases of birth-related trauma. Radiologic examination of the temporal bone may reveal evidence of fracture, tumor, stenosis, or other malformations in extremely rare cases but will not contribute to a decision to treat any particular functional deficiency. Consequently, these tests should be obtained judiciously, especially in the newborn.
Electrophysiologic examination may offer some insight into the status of the facial nerve in the days and weeks after birth. These tests are done to primarily differentiate between a posttraumatic palsy and developmental paralysis. Accordingly, a high index of suspicious should predate the ordering of neurologic stimulation studies. Electromyography, the most commonly used tool for most peripheral nerve disorders, records motor unit potential response to an electrical stimulus as well as spontaneous activity. This test becomes increasingly insightful many weeks after an injury, precluding its use as an immediate discriminator of injury. Electroneurography will differentiate acute injury from developmental disease by giving normal results in the former process while revealing little to no function in the latter.
Causes
Paralysis of the facial nerve identified at birth is either posttraumatic or developmental. Cranial nerve VII palsies stemming from birth-related injuries are almost exclusively unilateral. As mentioned previously, these have been historically linked to the use of obstetrical forceps. Other factors can include arrested descent of labor or positional injury. Initial physical examination will usually reveal some cutaneous manifestation of an adverse perinatal event. When coupled with the appropriate historical findings, a traumatic etiology for the observed paresis must be suspected.
Developmental causes are either isolated or syndromic. These account for an extremely small minority of cases but can present across the clinical spectrum, ranging from unilateral to bilateral, mild to severe, one facial nerve branch or all. Of the many isolated syndromes that can present with facial weakness or paralysis, Möbius syndrome is the most dramatic. Occurring in only 1 out of 50,000 live births, these patients often have bilaterally complete loss of facial nerve function and have no ability to trigger any degree of facial movement. The effect is immediately profound and worsens with time. In this particular syndrome, the abducens nerve (cranial nerve VI) is affected as well and compromises eye movement and coordination. Other possible nerve deficits, however rare, may include cranial nerves V, IX, X, and XII. Patients afflicted with Möbius syndrome, aside from lacking any facial expression, will suffer from the following in various degrees: drooling, deficiency of bilabial speech, sucking, swallowing, dry eyes, strabismus, and dental problems. Associated anomalies include cleft palate, club foot, syndactyly, auditory problems, and, even more rarely, Poland syndrome. Males and females are affected equally. While there seems to be a slight increased risk in the offspring of those affected, there is no identifiable genetic locus and no specific laboratory marker for disease identification. Intellectual capacity does not seem to be impaired in children afflicted.6
Other causes or associated conditions attributed to congenital facial weakness include hemifacial microsomia, velocardiofacial syndrome, DiGeorge syndrome, osteopetrosis (Albers-Schonberg disease), CHARGE syndrome (c olobomata, h eart disease, a tresia of choanae, r etarded growth, g enital hypoplasia, and e ar anomalies), facioscapulohumeral muscular dystrophy, congenital unilateral lower lip paralysis/asymmetric crying facies, and the maternal use of teratogens including thalidomide and misoprostol.7–11
Therapy
Conservative
Once a diagnosis of congenital facial paralysis is made, therapy in the neonatal period is completely supportive. Ophthalmological concerns involve protection against dry eye, corneal irritation, and outright exposure leading to abrasion. Frequent exams with lacrimal tear support throughout the day are recommended. As these children grow, speech therapy and careful dental hygiene monitoring are essential. Patients with unilateral lower segment palsies can be managed expectantly with administration of Botox periodically given to relax the depressors on the normal side.
Surgical
Urgent Intervention
When a unilateral facial paralysis is positively attributed to birth trauma, iatrogenic or otherwise, surgical intervention might be considered in a very small number of circumstances. Fortunately, 9 of 10 cases will resolve spontaneously. While early surgical decompression has not been proven advantageous over observation, those patients who have suffered from temporal bone fracture documented on computed tomography scan with abnormal electrophysiological testing in the postpartum period and again in the second month of life may be candidates. In those rare circumstances where surgery is being contemplated in the acute phase after diagnosis, simple decompression of the temporal bone at the fracture site is, by far, the most straightforward approach possible. Problems arise in this environment stemming from our inability to differentiate the degree of internal architectural injury to the nerve. Once having decompressed the temporal bone, grossly visible anatomic disruption of the nerve must be addressed by debridement of the affected segment and either reapproximation of the nerve directly or interpositional nerve grafting using autologous donor nerve such as the sural, greater auricular, or either antebrachiocutaneous branch. Nerve reapproximation and neurorrhaphy or interpositional nerve grafting, all in the total absence of tension, is thought to be of paramount importance toward maximizing any chance of axonal regeneration.
In those rare instances where it is determined that proximal injury has precluded any chance of ipsilateral facial nerve regrowth, cross facial nerve grafting (CFNG) should be considered. This can be done as a one- or two-staged procedure. Targeted donor and recipient branches can be matched but rapidly increase the degree of complexity of the reconstructive procedure. Transposition of the ipsilateral hypoglossal to the distal segment of the injured facial nerve while waiting for CFNG regrowth is commonly accepted.12
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