eMedicine Specialties > Otolaryngology and Facial Plastic Surgery > Reconstructive Surgery

Congenital Facial Paralysis

Author: Kim Lundstrom, MD, Consulting Staff, Department of Otolaryngology-Head and Neck Surgery, Longmont Clinic
Coauthor(s): Gregory C Allen, MD, Assistant Professor, Department of Otolaryngology-Head and Neck Surgery, University of Colorado School of Medicine
Contributor Information and Disclosures

Updated: Jun 8, 2006

Introduction

Facial paralysis in the newborn is uncommon, occurring in 0.23-1.8% of live births. In patients with congenital facial paralysis, it is important to determine the etiology of the paralysis because prognosis and treatment differ for traumatic and developmental causes. History and physical examination can often resolve the origin; however, radiographic imaging and tests of neuromuscular function may be necessary in planning treatment.

Problem

Congenital facial paralysis may cause multiple problems for the infant. Isolated facial paralysis causes difficulty with eye closure, potentially leading to corneal ulcerations. Difficulty with the orbicularis oris, depressor anguli oris, and depressor labii inferioris can lead to feeding difficulties. Associated anomalies include abnormalities of the external ears, severe inner ear abnormalities, maxilla and mandible hypoplasia, and cleft palate and vocal cord dysfunction with subsequent aspiration. When evaluating infants with facial paralysis, performing an extensive physical examination to exclude any other congenital malformations and to guide further care is important.

Frequency

The prevalence ranges from 0.23-1.8% of live births. Of these births, 78-90% are associated with birth trauma. Of the patients with palsies related to birth trauma, 91% are associated with forceps delivery. However, Smith et al evaluated 94 cases of neonatal paralysis and found that 25% occurred in either vaginal or cesarean section deliveries. Congenital unilateral lower lip palsy (also referred to as velocardiofacial [VCF] syndrome in some references) is the most common of the developmental lesions, occurring in 1 out of 120-160 live births.

Etiology

Congenital facial paralysis can be associated with traumatic or developmental causes. The traumatic causes are related primarily to a difficult labor.

Intrauterine trauma can occur from pressure on the infant's face by the sacral prominence during the birthing process. Supranuclear palsy has been shown to be associated with intracranial hemorrhage during the perinatal period. Injury most often results from the narrowing of the vertical segment of the facial canal. The facial nerve is also susceptible to trauma as it exits the stylomastoid foramen where soft tissue compression can lead to a transient facial neurapraxia.

The causes of developmental facial nerve paralysis are numerous and include mononeural agenesis, congenital paralysis, and congenital unilateral lower lip paralysis (CULLP). When CULLP occurs with cardiac anomalies, the condition is referred to as VCFl syndrome in some references.

Deficits associated with facial nerve paralysis

• Möbius syndrome: A broad spectrum of clinical and pathological findings characterize this syndrome. Presentation ranges from bilateral paralysis of the facial nerve (usually) with unilateral or bilateral palsy of the abducens nerve. This syndrome may also affect cranial nerves IX, X, and XII, as well as other extraocular motor nerves. It often involves abnormalities of the extremities, including absence of the pectoralis major muscle in Poland syndrome.
• Hemifacial microsomia: Several subcategories exist that fall under the spectrum of oculoauriculovertebral disorders. Vertebral anomalies and epibulbar dermoids characterize Goldenhar syndrome. Lower facial weakness occurs in 10-20% of cases, which is likely related to bony involvement in the region of the facial canal.
• Poland syndrome: This syndrome includes Möbius syndrome with congenital absence of the pectoralis major muscle.
• Goldenhar syndrome: This syndrome is a nonhereditary congenital variant of hemifacial microsomia. This condition includes additional findings of vertebral anomalies and epibulbar dermoids.
• DiGeorge syndrome
• Albers-Schönberg disease: Osteopetrosis, a rare cause of paralysis at birth, may manifest later in childhood.
• Trisomy 18, trisomy 13
• CHARGE syndrome: This acronym stands for colobomata, heart disease, atresia of choanae, retarded growth, genital hypoplasia, and ear anomalies. Multiple cranial nerves may be involved in this condition. At least 1 cranial nerve is involved in 75% of cases, and 2 or more cranial nerves are involved in 58% of cases. Of patients who have cranial nerve involvement, 60% involve cranial nerve VIII, 43% involve cranial nerve VII, and 30% involve cranial nerves IX and X.
• Muscular dystrophy: This condition is a steadily progressive familial distal myopathy associated with weakness of the face, jaw, neck, and levators of the eyelid. At birth, infants present with facial diplegia; however, lateral gaze is intact (in contrast to Möbius syndrome). Later in childhood, distal progressive myopathy develops.

Systemic or infectious conditions associated with facial nerve paralysis

• Melkersson-Rosenthal: This condition involves recurring attacks of unilateral or bilateral facial paralysis, swelling of the lips, and furrowing of the tongue. Angiotensin-converting enzyme is elevated during attacks.
• Poliomyelitis
• Infectious mononucleosis
• Varicella
• Acute otitis media
• Mastoiditis
• Meningitis
• Bell palsy

Teratogens associated with facial nerve paralysis

Thalidomide embryopathy: This sedative is administered at 28-42 weeks' gestation and is associated with phocomelia, arrested development of the ear, and paralysis of the facial and abducens nerves.

Misoprostol: This synthetic prostaglandin E1 analogue is used to prevent and treat gastric ulcers and gastrointestinal lesions induced by nonsteroidal anti-inflammatory drugs (NSAIDs). It may stimulate uterine contractions and has been used with mifepristone or methotrexate to induce abortion. When used alone, up to 80% of pregnancies continue to term. In a study of 96 infants with Möbius syndrome and 96 infants with neural tube defects, 49% of infants with Möbius syndrome were exposed to misoprostol in utero compared to 3% of infants with neural tube defects. The cause of Möbius syndrome associated with misoprostol may be vascular disruption of the subclavian artery in week 4-6, causing an ischemic brain event.

Pathophysiology

Möbius syndrome

Autosomal dominant inheritance with variable expression and incomplete penetration has been suggested as a cause of Möbius syndrome; however, most cases are sporadic. Four patients with Möbius syndrome reported peripheral neuropathy and hypogonadotropic hypogonadism. Malformations of the limbs and other cranial nerves are often associated with this syndrome. Several theories regarding the pathogenesis of Möbius syndrome are as follows:

• Aplasia or hypoplasia of cranial nerve nuclei
• Nuclear destruction
• Peripheral nerve abnormality
• Primary myopathy
• Disruption sequence in vascular territory of subclavian artery

Autopsy studies have supported all of the causes listed above. The wide range of presentations can be attributed to the variable causes. Pathologic studies have shown defects in cranial nerve nuclei with normal musculature and primary hypoplasia of muscles but a normal central nervous system.

Congenital unilateral lower lip paralysis

A patient with CULLP presents with drooping of the lower lip toward the unaffected side when laughing or crying and normal appearance of the face at rest. CULLP can appear in clusters with cardiac anomalies, which should provoke an evaluation for VCF. In VCF, microcephaly is present in 40% of cases, malar flatness is present in 70% of cases, vertical maxillary excess is present in 85% of cases, and Robin sequence is found in 15% of cases. The most common cardiac anomaly is ventricular septal defect (VSD), which occurs in 65% of cases. The etiology of CULLP is most often is attributed to hypoplasia or congenital absence of the depressor anguli oris or the depressor labii inferioris muscle. A second theory proposes that a primary brainstem infarction occurs and causes secondary hypoplasia of the musculature.

Trauma

Facial palsy is caused by compression of diploic bone of the mastoid process where the facial nerve is located superficially in infants. Complete transection caused by birth trauma is rare; therefore, surgical exploration is not indicated immediately. The site of injury may be intracranial, intratemporal, or extratemporal.

Presentation

Congenital facial nerve paralysis can be diagnosed based on birth history, family history, physical examination, and radiologic and neurophysiologic tests. Often, a mild paresis of the facial nerve is not noted at birth, especially if the injury is bilateral. When facial nerve paralysis is associated with hemifacial microsomia or other craniofacial abnormalities, the facial nerve is often not noted to be weak until the child grows and a more pronounced asymmetry develops, prompting closer evaluation of the facial nerve.

Obtain a thorough birth history in congenital facial paralysis is important. When the etiology is traumatic, evidence often supports difficult labor caused by cephalopelvic disproportion (CPD). Risks for difficult labor from CPD include primiparity and birth weight more than 3500 g. The use of middle forceps delivery (as opposed to low forceps) also increases the risk of injury to the facial nerve, as does prolonged second-stage labor.

Physical examination often reveals ecchymosis, hemotympanum, facial swelling, and severe head molding—all of which support difficult labor. These findings may be an indication that trauma caused the facial paralysis.

In addition to obtaining a birth history, a family history is important. A family history positive for facial paralysis or other congenital anomalies can increase the suspicion for a developmental cause of the facial paralysis. Hemifacial microsomia, Möbius syndrome, and oculoauriculovertebral dysplasia are some of the developmental causes of facial paralysis that would have additional findings on physical examination.

Physical examination may reveal other cranial nerve abnormalities, abnormal auditory brainstem response (ABR) (waves I-III or I-V), and any other congenital anomaly. Bilateral facial palsy is frequently incomplete, with the lower portion of the face usually less affected than the upper part. This distinguishes developmental causes of congenital facial paralysis from traumatic causes, which often involve the upper and lower face equally and are often unilateral. No evidence of birth trauma is present.

The House-Brackmann grading system is used to grade facial nerve paralysis as follows:

• Grade I - Normal
• Grade II - Mild dysfunction, slight weakness on close inspection, normal symmetry at rest
• Grade III - Moderate dysfunction, obvious but not disfiguring difference between sides, eye can be completely closed with effort
• Grade IV - Moderately severe, normal tone at rest, obvious weakness or asymmetry with movement, incomplete closure of eye
• Grade V - Severe dysfunction, only barely perceptible motion, asymmetry at rest
• Grade VI - No movement

Relevant Anatomy

Embryogenesis

The facial nerve develops early in fetal life from the facioacoustic crest in the second branchial arch. All facial muscles are identifiable in the embryo by the 14th week. The facial nerve develops close to the vestibulocochlear nerve and both of the internal and external ears. Therefore, any abnormality of these structures often accompanies facial nerve deficits. At term, the anatomy of the facial nerve approximates the adult anatomy, with the exception of its superficial location within a poorly pneumatized mastoid. Development of the mastoid bone occurs from age 1-3 years and displaces the facial nerve medially and inferiorly.

Anatomy

The facial nerve is a mixed nerve containing motor, sensory, and parasympathetic fibers. The motor nucleus lies deep within the reticular formation of the pons, where it receives input from the precentral gyrus of the motor cortex. The motor fibers innervate the muscles of facial expression, posterior belly of the digastric muscle, stylohyoid muscle, and the stapedius muscle. The upper motor neuron tracts supplying the upper face cross once and then cross again in the pons; thus, bilateral innervation is present, whereas tracts to the lower face cross only once.

The parasympathetic fibers originate in the superior salivatory nucleus and are responsible for lacrimation and salivation via the greater superficial petrosal nerve and the chorda tympani, respectively. Afferent taste fibers are carried from the anterior two thirds of the tongue to the nucleus tractus solitarius via the lingual nerve, chorda tympani, and nervus intermedius. The facial nerve also provides some sensory innervation of the external auditory canal.

Segments of the facial nerve

The intracranial segment travels from the brain stem at the level of the caudal pons to the internal auditory canal (IAC), a distance of 23 mm. The meatal segment includes the portion of the nerve between the fundus of the IAC and the meatal foramen. The facial nerve occupies the anterior/superior quadrant within the IAC. The labyrinthine segment is 3-5 mm in length and travels to the geniculate ganglion. The first branch of the facial nerve (ie, greater superficial petrosal nerve) is within this segment. Importantly, the bony fallopian canal is narrowest within the labyrinthine segment of the nerve.

The tympanic segment begins at the geniculate ganglion where the nerve turns 40-80° posteriorly (first genu) to enter the middle ear and ends at the pyramidal eminence. Traumatic causes of facial nerve paralysis are found most commonly in the perigeniculate region. The nerve turns inferiorly (second genu) below the horizontal semicircular canal and continues as the mastoid (vertical) portion, which is 10-14 mm in length and travels to the stylomastoid foramen. The extratemporal portion of the facial nerve is distal to the stylomastoid foramen and supplies the muscles of facial expression. The facial nerve divides the parotid gland into superficial and deep lobes. Within the gland, branching of the nerve is variable. Most commonly, the nerve divides into an upper temporozygomatic and lower cervicofacial division. Five terminal branches innervate the mimetic musculature of the face, namely, temporal, zygomatic, buccal, marginal mandibular, and cervical.

Upper motor neuron lesions of the facial nerve occur at any point from the motor cortex proximal to the facial nucleus. Clinically, upper motor neuron lesions result in muscle sparing in the upper portion of the face but involvement of the lower two thirds of the facial mimetic musculature.

Lower motor neuron lesions of the facial nerve occur at the level of the facial nucleus or distal to the nucleus. These lesions involve all the motor branches, which results in total hemiparesis. Lesions near the geniculate ganglion lead to paralysis, hyperacusis, and alteration of lacrimation, salivation, and taste. Lesions distal to the greater superficial petrosal branch cause paralysis associated with alteration in taste; however, lacrimation is normal. Extracranial injuries lead to individual deficits depending on the involved branch.

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