Keywords
Asymmetric crying facies, Bell’s palsy, blink responses, brainstem, facial EMG, facial nerve, facial microsomia, Lyme disease, Moebius syndrome
Introduction
Facial palsy is one of the most frequent mononeuropathies in the pediatric age group. The diagnosis of idiopathic benign Bell’s palsy is based on exclusion of other acquired central or peripheral nervous system conditions, some of which have more ominous implications. Facial paralysis in a newborn may be due to prenatal or obstetric stress to the nerve. Congenital facial weakness or asymmetry may also reveal a recognizable malformation syndrome or congenital neuromuscular disorder. Any child who has either a congenital or acquired facial weakness requires a detailed general and neurologic examination complemented with neurophysiologic, neuroimaging, auditory, and other laboratory studies. Because of significant functional and esthetic consequences, the evaluation of a child with facial paralysis requires that major emphasis be placed on early etiologic definition, therapeutic decisions, and a reliable prognostic assessment.
Evaluation of the Facial Nerve in Children
Anatomy
The facial nerve ( Figure 13.1 ) emerges from multiple functionally specialized ventrolateral brainstem nuclei. The motor nucleus of cranial nerve VII originates in the caudal pons. Five groups of cells are defined, corresponding to a topographic organization of motor neurons innervating different muscles. The ventral groups of cells supply the periorbital muscles; the dorsal groups supply the perioral muscles. Taste fibers for the anterior two-thirds of the tongue, and sensory fibers from the external acoustic canal, project to the upper part of the nucleus of the tractus solitarius in the vicinity of the motor nucleus of cranial nerve VII. The lacrimal, sublingual, and submandibular preganglionic parasympathetic fibers of the facial nerve originate in the nearby superior salivary nucleus. The twin sensory and motor roots of the facial nerve emerge from the brainstem at the level of the bulbopontine sulcus, between the sixth and eighth cranial nerves, at the cerebellopontine angle, then enter the pars petrosa ossis temporalis via the internal acoustic meatus and follow a common path in the first part of the facial canal. The sensory components enter the geniculate ganglion at this level. Motor fibers of the facial nerve traverse peripherally through the internal auditory canal in the temporal bone, in company with the nervus intermedius, consisting of the sensory fibers of cranial nerve VII as well as with the VIIIth cranial nerve. The greater petrosal nerve arises from the labyrinthine segment of the facial nerve and carries parasympathetic fibers to the pterygopalatine ganglion, where it synapses and sends fibers to the lacrimal gland. More distally, the facial nerve’s mastoid segment travels inferiorly and laterally to the jugular fossa. Here, the stapedius nerve arises to innervate the stapedius muscle. The facial nerve gives off the chorda tympani in the distal mastoid segment. The chorda tympani then passes through the middle ear to supply afferent taste fibers to the anterior two-thirds of the tongue, as well as parasympathetic fibers to the submandibular and sublingual glands. The primary motor bundle of the facial nerve traverses the second and third parts of the facial canal alone. The facial motor nerve emerges from the skull at the stylomastoid foramen, gives off the posterior auricular branch, and then divides into two main terminal branches in the parotid gland. The inferior cervicofacial branch passes down along the mandible to supply the muscles in the lower part of the face, giving off a buccal branch to the risorius, the buccinator, and the orbicularis oris muscles; a mental branch to the depressor anguli oris, the depressor labii inferioris, and the mentalis muscles; and a cervical branch to platysma. The superior temporofacial branch runs horizontally forward, giving off frontal branches to the frontalis and orbicularis oculi muscles; suborbital branches to the levator labii superioris, zygomaticus, levator anguli oris, and dilatator naris muscles; and buccal branches to the buccinator and orbicularis oris muscles. Although there is considerable diversity in its trajectory and divisions, cranial nerve VII innervates all muscles of facial expression except the levator palpebrae superioris. The close anatomic proximity of cranial nerves V, VI, VII, and VIII in the brainstem and cerebellopontine angle explains the involvement of multiple nerves in malformations, and in ischemic or compressive disorders. Interneuronal and synaptic V–VII connections in the brainstem provide the basis for the neurophysiologic studies exploring the blink reflex. The geniculate ganglion, located within the internal auditory canal, contains the soma of sensory facial fibers. Reactivation of viral particles latent in the geniculate ganglion is believed to be involved in the pathogenesis of idiopathic and Ramsay Hunt facial palsies. Lesions of the facial nerve trunk localized distal to the ganglion may involve different facial nerve branches (i. e. greater superficial petrosal nerve, nerve to stapedius muscle, and chorda tympani), causing variable dysfunction of lacrimation, salivation, taste, and/or hearing. Nerve entrapment is most likely to occur at the narrowest intraosseus segment, the meatal foramen, where it is not protected by epineurium and perineurium.
Clinical Examination
Newborn and Young Infants
In a newborn patient with unilateral facial palsy, the face may appear symmetrical at rest. Examination on crying, however, reveals mouth deviation, failure to completely close the eye, and a wider palpebral fissure on the nonaffected side. Absence of the fine dilatory movements of the nostril synchronous with breathing, an asymmetrical searching reflex, asymmetrical closing of the lips over the pacifier, and absence of frontal wrinkling on the nonaffected side may be also noted. Clinical features suggesting a possible traumatic origin include mastoid, pre-auricular, or temporal hematoma; otorrhagia; or hemotympanum. If there is fever and sensitivity to pressure over the pre-auricular area, or a context of maternal-fetal infection, neonatal otitis media must be excluded. Associated dysfunction of other cranial nerves, mandibulofacial or ocular malformations, or signs of any systemic dysfunction may provide information relevant to both etiology and prognosis. Also, an ophthalmologic examination may detect ocular malformations, subtle oculomotor dysfunction, or a retinal defect that may characterize a specific congenital malformation syndrome or embryofetopathy.
Older Children
Facial palsies in older children are typically characterized by inability to close the eye, disappearance of the nasolabial fold, and deviation of the mouth. Associated features such as decreased tearing, hyperacusis, and loss of taste sensation may help to localize the seventh nerve lesion. The topography and severity of a facial palsy is assessed by observing the response to commands activating the different branches of the facial motor nerve: closing the eyes, elevating the eyebrows, frowning, showing the teeth, puckering the lips, and tensing the soft tissues of the neck. A standardized assessment scale, such as the House-Brackmann grading system, may be useful to define severity and record progress. A full neurologic examination aims to rule out involvement of other cranial nerves or a more widespread neurologic process. The general physical examination includes evaluation of mastoid and parotid areas, visualization of the external auditory canal, and inspection of the tympanic membrane. Mass lesions, inflammation, or infection may lead to facial nerve injury; vesicles or scabby skin may implicate zoster virus infection. The ophthalmologic examination searches for concomitant conjunctival or corneal complications, or signs of increased intracranial pressure.
Clinical-Anatomic Relationships
When partial or complete facial paralysis has developed, associated features may help in distinguishing central from peripheral palsies, and determining the specific site of the lesion in the cranial nerve VII pathways or nucleus. Lesions in the pons may induce hyperacusis due to dysfunction of motor fibers to the stapedius muscle, and may progress to other features of brainstem involvement. A lesion between pons and geniculate ganglion may produce hyperacusis and impairment of lacrimation, salivation, and taste of the anterior two-thirds of the tongue. Between the geniculate ganglion and stapedius nerve, hyperacusis and impairment of salivation and taste are expected, with preservation of lacrimation. Between the stapedius nerve and chorda tympani, salivation and taste will be impaired but hearing is normal. Beyond the exit of chorda tympani, the only symptom will be facial weakness.
Central facial palsies (suprabulbar) show more widespread clinical features and a progressive course. Upward and outward eye movement when blinking (Bell’s sign) is usually absent. Typically, spontaneous facial expression, such as smiling as an emotional reaction, is preserved, while no voluntary movement is obtained in response to a command, such as asking the patient to smile.
Complementary Investigations
Congenital facial palsies (CFPs) have a more standardized diagnostic algorithm than acquired facial palsies (AFPs). Most CFPs are either related to a congenital malformation or are of traumatic origin. A combination of neurophysiologic tests and neuroimaging provides an opportunity for early diagnosis, management, and determination of prognosis, but their use in AFPs is still controversial. Globally, electrodiagnostic studies are used to search for prognostic indicators. Magnetic resonance imaging (MRI) is mandatory in traumatic cases or whenever an intracranial lesion is suspected. Cerebrospinal fluid (CSF) examination is not a routine test but may be useful to rule out neoplastic, infectious, or inflammatory meningeal involvement. Polymerase chain reaction (PCR) of serum, CSF, or saliva may allow early detection of Lyme disease, varicella or other herpes viruses, taking into account geographical and seasonal differences.
Middle Ear and Auditory Investigations
Several noninvasive tests are useful in young children with no localizing symptoms and in older patients with associated hearing loss or nonspecific ear complaints. These studies provide a means to localize the facial nerve lesion, search for middle ear infection or trauma, and define concomitant eighth cranial nerve involvement. Otoscopy will determine the presence or absence of outer and middle ear disease. Impedance audiometry evaluates the middle ear system. The acoustic-stapedial reflex (AR) is easy to perform at any age and detects the contraction of the ipsilateral stapedius muscle in response to a high level stimulus (70 to 90 dB) at different frequencies. Results are shown as absent reflex, reflex requiring thresholds over 90 dB, and normal response. Absence of AR is expected if the lesion is proximal to the branching of the nerve to stapedius muscle. Abnormal AR during the first week after clinical onset has been associated with worse recovery of AFP. Pure-tone and speech audiometry can detect hearing loss. In infants or uncooperative children, hearing thresholds may be evaluated by transiently evoked otoacoustic emissions. Brainstem auditory evoked responses (BAERs) can be performed at any age, and are useful for measuring auditory thresholds and studying retrocochlear auditory pathways. The Schirmer lacrimation test, the salivary flow test, and electrogustometry are not routinely undertaken in young children.
Imaging Studies
In CFPs, MRI is used mainly to rule out associated cerebral lesions or posterior fossa malformations, although it may reveal abnormal signal in the area of the seventh cranial nerve nucleus or other minor cerebral anatomic defects. In AFPs, imaging is particularly valuable when there are otoscopic findings of a mass in the middle ear or a history of chronic otitis media, previous mastoid surgery, or trauma. High-resolution computed tomography (CT) is the best method to study the course of the facial nerve through the petrous bone, and detect a fracture line or posttraumatic hemorrhage. Pre- and postcontrast MRI is used to investigate the brainstem, cranial nerves, and parotid gland. MRI will be required in the presence of complicated otitis media, multiple cranial mononeuropathies, recurrent ipsilateral facial paralysis, progression beyond three weeks, absence of improvement after 6 months, development of facial hemispasm or other neurologic signs, or retrocochlear abnormalities in the BAERs. Contrast enhancement of the geniculate ganglion within the labyrinthine segment of the facial nerve is a common finding in Bell’s palsy, although some enhancement, especially of the first genu and proximal tympanic segment, may also be seen in normal subjects. Herpes zoster may be suspected, even in the absence of vesicular eruption, if the enhancement is localized to the inner ear structures.
Facial Nerve Conduction Studies and Electroneuronography
These techniques are used to determine the characteristics and severity of the lesion, and give clues regarding the timing of injury. Facial nerve conduction studies (FNCSs) assess function of the extracranial portion of the facial nerve. For FNCSs, surface electrodes are placed over facial muscles to record the response elicited by an electrical stimulus applied to the facial nerve. A brief square wave electric shock (0.2 ms) of supramaximal intensity (20–60 mA) is used for cervicofacial branch FNCS, applied first at a point anterior to the tragus, and then at a point along the horizontal portion of the mandible, recording responses from the orbicularis oris muscle. Normal values are available from birth to age 15 years. The facial nerve conduction velocity (NCV) increases markedly during growth, particularly within the first year of life. Electroneuronography (ENOG) uses surface electrodes placed along the nasolabial fold over the nasalis and perioral muscles to record the response elicited by a brief supramaximal electrical stimulus applied to the facial nerve near the stylomastoid foramen. The peak-to-peak amplitude of the compound muscle action potential (CMAP) is recorded as a percentage of the amplitude of the contralateral normal side. This percentage is presumed to correspond to the number of surviving motor neurons. Asymmetry greater than 30% is considered abnormal. FNCSs and ENOG have shown prognostic value in complete acute nontraumatic unilateral facial paralysis in childhood. In idiopathic AFPs, amplitudes reach their nadir 7 to 14 days after the onset of weakness. Hence, the extent of Wallerian degeneration may be defined as early as 7 days after the onset of Bell’s palsy. In CFPs, serial FNCSs and ENOGs help distinguish fixed developmental defects from recovering traumatic insults.
Needle Electromyography of Facial Muscles
Conventional needle electromyography (EMG) confirms neurogenic dysfunction of the facial muscles and provides a means to evaluate outcome and assist surgical decisions. At birth, a prenatal denervation process should be suspected when fibrillation potentials are recorded before the fourth day of life. In newborn and young infants, EMG can detect facial palsies that are not apparent clinically. At any age, EMG is particularly useful during the second and third weeks after onset of the facial palsy, once Wallerian degeneration has occurred. Later on in the course of recovery, changing EMG patterns demonstrate nerve regeneration and muscle reinnervation. Needle EMG examination is performed at rest, and with voluntary contraction or after stimulation. Stimulation-detection EMG is very useful in young children who do not cooperate, as well as in very severe palsies with no apparent voluntary recruitment of motor unit potentials (MUPs). The EMG activity is recorded by a concentric needle electrode in at least one muscle innervated by the temporofacial branch (orbicularis oculi, frontalis), and in another innervated by the cervicofacial branch (orbicularis oris, depressor anguli oris). Fasting the baby for up to 4 hours before the test may allow recording bursts of activity arising from the facial muscles while the baby is crying or sucking a pacifier. In older children, voluntary contraction can be recorded after asking the child to imitate the examiner when closing the eyes, smiling, and whistling.
Blink Responses
This technique explores both facial and trigeminal nerve functions, as well as the pathways between their respective cranial nuclei within the brainstem. Numerous studies indicate the value of blink responses (BRs) for detecting brainstem dysfunction and predicting clinical outcome in adult patients with facial palsies. This study is particularly useful during the early stages of nerve regeneration, when the persistence or return of BRs suggests satisfactory recovery. The blink reflex results from the contraction of the orbicularis oculi muscle provoked by stimulation of the supraorbital branch of the trigeminal nerve. A single electric shock is applied to the supraorbital foramen to elicit BRs recorded from the orbicularis oculi muscle on both sides. Stimulation of the ipsilateral cranial nerve V provokes a direct response with two components: R 1 , which is immediate and brief, and R 2 , which is delayed and longer lasting. Stimulation of the contralateral nerve V provokes a crossed R 2 response. The maturation from birth of the electrically elicited BRs has been studied. The R 1 response is always present, whatever the age, and its latency achieves normal adult values at term birth. The ipsilateral R 2 response can be evoked in most newborns and infants, but the contralateral R 2 response is not always obtained before the age of 8 months. The R 1 component corresponds to an oligosynaptic reflex arc involving at least 2 and no more than 3 synapses in the pons between the main sensory nucleus of cranial nerve V and the motor nucleus of the ipsilateral cranial nerve VII. The R 2 component follows polysynaptic medullary pathways, which are more caudal and closer to the bulbar formations. The spinal trigeminal nucleus has projections to the adjacent paramedian reticular formation and the motor nuclei of both seventh nerves. Injury in the trigeminal pathway leads to delayed or absent ipsilateral R 1 and R 2 responses, and contralateral R 2 response, while a lesion in the facial pathway shows delayed ipsilateral R 1 and R 2 , but normal contralateral R 2 . Lesions at the pons show ipsilateral abnormal R 1 response, while contralateral stimulus has normal R 1 . Lateral medullary lesions show abnormal R 2 response on the affected side, stimulating either the nonaffected or the affected side.
Congenital Facial Palsies
The incidence of CFPs ranges from 1.8 to 7.5 per thousand births. The differential diagnosis includes intrauterine compression, obstetric trauma, and congenital malformation syndromes ( Box 13.1 ). Most children with a facial palsy secondary to a congenital malformation present with other associated physical anomalies. Congenital facial asymmetry may also result from hypoplasia of the depressor anguli oris muscle (DAOM).
Birth Trauma
- •
Facial nerve injury: obstetric trauma or intrauterine stress
- •
Neonatal encephalopathy
- •
Posterior fossa hematoma
Developmental Defect
- •
First and second branchial arch malformation syndromes: facio-auriculo-vertebral spectrum, hemifacial microsomia, mandibulofacial dysostosis
- •
Asymmetric crying facies: hypoplasia of the depressor anguli oris muscle, cardiofacial syndrome, 22q11 deletion
- •
CHARGE association – Colobomata, Heart disease, Atresia of the choanae, Retarded growth or development, Genital hypoplasia, Ear anomalies
- •
Moebius syndrome
Neuromuscular Disease
- •
Congenital myotonic dystrophy
- •
Congenital muscular dystrophy
- •
Congenital myopathies: nemaline, myotubular, fiber-type disproportion
- •
Facioscapulohumeral muscular dystrophy: early-onset type
- •
Congenital myasthenic syndromes
- •
Neonatal transient myasthenia gravis
Perinatal Facial Nerve Injuries
Forceps delivery, prolonged labor, a birth weight above 3500 g, and primiparity are significant risk factors for CFP. In a retrospective study of 172 children with congenital facial asymmetry, 67% had facial mononeuropathy with no associated malformation. The face was often symmetrical at rest but cry revealed the unilateral absence of brow puckering, incomplete eyelid closure, and asymmetry of the mouth ( Figure 13.2 ). More than the half of patients with nonsyndromal CFP were born by forceps delivery. A neonatal purulent otitis media was diagnosed in two neonates. In the remaining patients, no causal factors were found. In such cases CFP may result from pre- or perinatal compression of the extracranial part of the VIIth nerve against the myometrium and fetal shoulder, or the sacral prominence of the maternal pelvis. In fact, there is often concordance between the side of CFP and that of cephalic presentation. MRI shows developmental abnormalities of the facial nucleus in a small proportion of children with isolated unilateral CFP.
Alterations in facial NCV and BRs, as well as needle EMG of facial muscles, precisely define the extent and severity of the facial nerve lesion. Moderate forms show only partial denervation and either affect the territories of the two main branches equally, or predominantly involve the cervicofacial branch. Severe forms show absent facial CMAPs and BRs, and very reduced or single EMG recruitment patterns.
Clinical and EMG monitoring of CFPs demonstrates that facial nerve regeneration and muscle reinnervation usually proceed slowly, over some months. The percentage values of facial function over time provided by serial ENOGs correlate with prognosis. When the palsy seems clinically to remain complete, EMG may indicate a more favorable outcome by showing nascent MUPs with the reappearance of a low-amplitude increased-latency motor response.
In our series, severe or moderate palsies showed a more favorable outcome in the group delivered without forceps than in the group delivered with forceps. Improvement in facial motor activity and EMG parameters may continue as long as 2 years after nerve injury. Surgery must be avoided if it is so early that it might preclude spontaneous recovery or if there is no focal lesion for which repair is possible. In contrast, one must not fail to recognize a definitive facial nerve lesion related to a specific area of focal compression. Even if CT and MR imaging fail to define a focal VII nerve lesion, surgical consideration is warranted if there are no signs of clinical or EMG improvement. In our series, surgical exploration was performed in eight infants with severe CFP who had no clinical improvement. In each case, two or three successive EMGs had demonstrated either the persistence of a major lesion of the two major facial nerve branches without any sign of recovery, or partial recovery of the cervicofacial branch with persistence of complete paralysis of the temporofacial branch. In two instances, surgical exploration identified facial nerve compression against a fracture line in the petrous temporal bone, associated in one case with chronic inflammation of the mastoid antrum. In the six other infants, the facial nerve trunk was altered—pale, thin, flattened—without any obvious local cause. In a retrospective study of children with unilateral isolated CFP who had incomplete, often very limited recovery by 5 years, there was no association between this poor outcome and risk factors for birth trauma to the VIIth cranial nerve. Case Example 13.1 and Case Example 13.2 illustrate the difficulties experienced when one considers surgical exploration in an infant with a severe CFP.
This baby boy was born at term with a breech presentation. A complete unilateral CFP was noted at birth. At age 3 months, slight mobility of the nasolabial fold and labial commissure appeared. The first EMG was performed at age 3 months 10 days. The orbicularis oculi muscle was inactive and did not respond to facial nerve stimulation. BRs were absent. In the orbicularis oris, a slight contraction was detected. Stimulation of cranial nerve VII elicited a low-amplitude normal-latency motor response. NCV of the cervicofacial branch was normal (25 m/s). The results of a second EMG, at age 6 months, were identical to the first. At 7 months, there was no clinical improvement. Exploratory surgery at 8 months identified lesions due to chronic inflammation of the mastoid antrum with compression of the second section of the seventh nerve by a bony spur secondary to a fracture line. There was no improvement postoperatively. Repeated EMGs at ages 10 and 21 months did not demonstrate reinnervation of either the orbicularis oculi or orbicularis oris. Clinical improvement was poor and very slow. Conjunctival infections ceased only at the age of 4 years. Facial asymmetry was still significant at age 10 years.
Comment
Given the findings on surgical exploration, it is likely that an earlier intervention would have improved the prognosis in this case.
A baby girl, born at term by forceps delivery, showed a complete unilateral CFP. The first EMG at 23 days of age revealed complete inexcitability of the orbicularis oris muscle, with no response to electrical stimulation of cranial nerve VII. An extremely reduced interference pattern was noted in the orbicularis oculi. Stimulation of nerve VII at the pretragal point elicited a low-amplitude CMAP in orbicularis oculi, with a markedly increased latency (16.1 ms). No BRs were elicited. At day 45, there was no significant clinical improvement and a second EMG was performed. The orbicularis oris muscle was still inactive and unresponsive. In the orbicularis oculi muscle, the interference pattern was still reduced, but showed a combination of several types of MUPs, and the CMAP showed a greater amplitude and shorter latency (10.0 ms). BRs were still absent. At 5 months, further clinical signs of recovery of facial motor activity were noted: the eyelids closed spontaneously with sleep and with stimulation during blink reflex testing, and the labial commissure elevated slightly in reaction to skin stimulation. The third EMG revealed signs of reinnervation in orbicularis oris; stimulation of the facial nerve at the pretragal point elicited a low-amplitude CMAP with moderately increased latency (7.6 ms). The cervicofacial branch NCV was normal (30 m/s). In orbicularis oculi, the contraction showed an intermediate recruitment pattern; the CMAP had normal morphology, amplitude, and latency, and the R1 component of the BRs had a normal latency. Recovery was clinically complete at 15 months.
Comment
This initially complete CFP in a newborn delivered by forceps resolved spontaneously. In this instance, early surgical intervention would have been pointless or counterproductive. The EMG recording of voluntary activity and a CMAP from the orbicularis oculi muscle in an early examination, even if it showed very poor activation and a very low-amplitude CMAP, can be considered predictive of a good outcome.
Asymmetric Crying Facies
Congenital facial asymmetry obvious only when the child is crying, and involving only the lower lip, has several potential causes. Diagnosis requires EMG needle examination. Most of the time, asymmetric crying facies (ACF) is due to hypoplasia of the DAOM. Typical findings are the absence of neurogenic EMG abnormalities, a low-amplitude interference pattern on crying, and normal facial NCV. Less often, EMG signs of partial denervation of the DAOM, depressor labii inferioris, and mentalis muscles are indicative of a distal partial facial palsy. The selective topography of these nerve lesions corresponds to the territory of the mental branch of the facial nerve. This branch, arising from the cervicofacial branch, has a course that in the fetus and newborn closely follows the horizontal part of the mandible and is thus easily compressed. Regardless of the cause, this clinical presentation is characterized by a labial commissure that does not descend on the affected side, but the nasolabial folds and contraction of the frontalis muscles are symmetric ( Figure 13.3 ). The lower part of the DAOM muscle inserts in a diffuse manner into the platysma muscle, along the base of the mandible, and enters as a narrow fascicle into the labial commissure, where its fibers merge with those of the orbicularis oris muscle. Its contraction draws the labial commissure and the external part of the lower lip downward and outward, producing an expression of displeasure. Hypoplasia of the depressor labii inferioris muscle may also be present. The association of ACF with congenital heart malformation has been termed the cardiofacial syndrome. Prospective studies of newborns with ACF have subsequently confirmed a higher risk of visceral malformation, particularly of the heart, great vessels, and genitourinary system. A deletion at 22q11 has been reported both with ACF as a part of the cardiofacial syndrome, and with isolated ACF. Thus, an EMG diagnosis of hypoplasia of the DAOM should lead to a search for associated visceral malformation(s). In a personal series of 51 children with ACF, EMG studies diagnosed a partial facial palsy in 10 patients, and revealed signs of hypoplasia of the DAOM in 41, associated with congenital malformations in 5 of the 41.
Finally, in certain cases of congenital facial asymmetry the EMG does not show any sign of paralysis or muscular hypoplasia. In these cases, asymmetry is noted both at rest and on crying, and no apparent malformations are observed. Such “pseudoparalysis” may be associated with asymmetric mandibular hypoplasia, but more often is the result of a restraint in intrauterine position or movement. A clinical feature characteristic of this situation is the loss of parallel symmetry of the gums ( Figure 13.4 ). Pseudoparalysis was identified in 5 of 172 infants in our congenital facial asymmetry series. EMG studies were normal in all, demonstrating the integrity of facial muscles and nerves. This functional asymmetry resolved rapidly in all 5 babies within the first 2 months.
Orofacial Malformations with Cranial Nerve Palsies
Hemifacial malformations involving the derivatives of the first and second branchial arches can result in lesions of cranial nerves V and VII ( Figure 13.5 ). Facial paralysis is present in most cases of Goldenhar syndrome [OMIM#164210], in 43% of infants with CHARGE syndrome (Colobomata, Heart disease, Atresia of the choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies) association due to CHD7 mutations [OMIM#214800], and in 22% of children with hemifacial microsomia. The authors have reported a series of 33 infants with asymmetric facial motor activity associated with hemifacial hypoplasia and ear malformation. In addition to Goldenhar syndrome and CHARGE association, clinical diagnoses in this series included the facio-auriculo-vertebral spectrum and Treacher-Collins-Franceschetti syndrome [OMIM#154500]. Facial weakness was either diffuse or localized to one side of the face. EMG activity was variably normal, neurogenic, or low-amplitude. Among the 19 infants with totally or partially denervated muscles, MRI or CT scan showed a piliferous cyst of the cerebellum in one case, and cerebellar hypoplasia in another. In the 14 infants with no sign of neurogenic atrophy, no abnormalities of the central nervous system were found. In hemifacial malformations, involvement of the facial nerve is a predictive sign of an associated malformation of the central nervous system, in particular of the posterior fossa.
Moebius Syndrome
Diagnosis of this syndrome is easy in cases of total or partial facial diplegia, whether symmetric or asymmetric, when it is associated with bilateral paralysis of abduction of the eye ( Figure 13.6 ). When the facial diplegia is partial, it usually predominantly involves the upper half of the face. A concomitant paralysis of the hypoglossal nerve with atrophy of the tongue is present in one-third of patients with Moebius syndrome. Most of these infants have congenital dysphagia, drooling, malocclusion, velopharyngeal incompetence, dysarthria, and delayed speech. Trigeminal nerve involvement, with temporal-masseter weakness or contracture, is less frequent. Club foot, malformations of the hands and fingers, and the Poland anomaly may be associated with the Moebius syndrome ( Table 13.1 ). Children with Moebius syndrome later suffer from the psychological consequences of esthetic damage, but the disorder usually is not associated with mental retardation and is not progressive. Most cases are sporadic, but families with autosomal dominant inheritance have been reported. Additionally, six patients with Moebius syndrome associated with an axonal peripheral neuropathy and hypogonadism have been described. Facial EMG is an important diagnostic tool contributing to the differential diagnosis and elucidation of the multifaceted pathogenesis of Moebius syndrome. If facial EMG is difficult to interpret secondary to muscle atrophy, study of the lingual and palatal muscles can be useful in identifying a concomitant neurogenic process in the territories of the hypoglossal nerve and pharyngeal plexus. EMG of the limbs distinguishes Moebius syndrome from congenital myotonic dystrophy or other myopathies.
| Clinical Findings | Number of Patients (percent) |
|---|---|
| Cranial nerve palsies | |
| Facial diplegia | 75/75 (100) |
| Symmetrical, 46 / asymmetrical, 29 | |
| Complete, 46 / Upper face, 26 / Lower face, 3 | |
| Abducens palsy | 68/75 (91) |
| Bilateral, 65 / Unilateral, 3 | |
| Ptosis | 3/75 (4) |
| Temporal-masseter weakness or contracture | 21/59 (35) |
| Sensory hearing loss | 6/75 (8) |
| Laryngeal or pharyngeal weakness | 28/72 (39) |
| Tongue atrophy | 47/71 (62) |
| Associated malformations | |
| Epicanthus | 73/75 (97) |
| Fingers | 33/75 (44) |
| Club foot | 30/75 (40) |
| Poland anomaly | 12/75 (16) |
| Toes | 3/75 (4) |
| Visceral | 8/75 (11) |
| Cleft palate | 2/75 (3) |
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
