Chapter 70. Disorders of the Facial Nerve

Facial nerve dysfunction can dramatically affect a patient's quality of life. The human face is a focal point for expression and interpersonal communication, whereas facial motor movement contributes to eye protection, speech articulation, chewing and swallowing, and emotional expression. Thus, the patient with a facial palsy suffers not only the functional consequences of impaired facial motion but also the psychological impact of a skewed facial appearance.

Essentials of Diagnosis

Bell's Palsy

• Acute onset, with unilateral paresis or paralysis of the face in a pattern consistent with peripheral nerve dysfunction (all branches affected).
• Rapid onset and evolution (<48 hours).
• Facial palsy may be associated with acute neuropathies affecting other cranial nerves (particularly, cranial nerves V–X).

Herpes Zoster Oticus (Ramsay Hunt syndrome)

• Acute peripheral facial palsy associated with otalgia and varicella-like cutaneous lesions that involve the external ear, skin of the ear canal, or the soft palate.
• Involvement often extends to cranial nerves V, IX, and X, and cervical branches that have anastomotic communications with the facial nerve.
• Differentiated from Bell's palsy by characteristic cutaneous ulcers and a higher incidence of hearing loss or balance dysfunction.

General Considerations

There are a variety of disorders that may be associated with unilateral facial palsies (Table 70–1). Bilateral facial palsy is much less frequent and occurs in less than 2% of patients presenting with an acute facial palsy (Table 70–2). Bilateral involvement typically reflects a systemic disorder with multiple manifestations. Because of their overlapping clinical presentation and treatment paradigms, Bell's palsy and herpes zoster oticus (also known as Ramsay Hunt syndrome) will be considered together.

Bell's Palsy

No identifiable cause is present for approximately 60–70% of cases of acute facial palsy. The clinical diagnosis of Bell's palsy is appropriately applied in such cases. Bell's palsy reveals several characteristics. The onset is that of an acute, unilateral paresis or paralysis of the face in a pattern consistent with peripheral nerve dysfunction (Figure 70–1). The onset and evolution are rapid—typically less than 48 hours. There may also be subtle but frequent associated dysfunction of cranial nerves V, VIII, IX, and X in association with Bell's palsy. Pain or numbness affecting the ear, mid-face, and tongue as well as taste disturbances are common. These observations suggest that the facial weakness seen in Bell's palsy is the inflammatory facial-motor component of a wider cranial polyneuropathy that is induced by viral agents admitted through mucosal membranes.

Recurrent facial palsy consistent with Bell's palsy occurs in 7–12.0% of patients. Ipsilateral recurrences approximate contralateral involvement. Recurrences are more likely in patients with a family history of Bell's palsy and the incidence of diabetes mellitus in recurrent Bell's palsy patients is 2.5 times that noted in nonrecurrent cases. Immunodeficiency is also associated with recurrences.

Herpes Zoster Oticus

Herpes zoster oticus (Ramsay Hunt syndrome) is a syndrome of acute peripheral facial palsy associated with otalgia and varicella-like cutaneous lesions. It accounts for approximately 10–15% of acute facial palsy cases. The lesions may involve the external ear, particularly the meatal and preauricular skin, the skin of the ear canal, or the soft palate. These findings establish the diagnosis (Figure 70–2). Hearing loss, dysacusis, and vertigo reflect extension of the infection to involve the eighth cranial nerve. Involvement often extends to other cranial nerves (V, IX, and X) and cervical branches (2, 3, and 4) that have anastomotic communications with the facial nerve. Herpes zoster oticus is therefore differentiated from Bell's palsy by the characteristic cutaneous changes and a higher incidence of cochleosaccular dysfunction.

Pathogenesis

Studies of the intratemporal facial nerve suggest that Bell's palsy and herpes zoster oticus most commonly result from the impaired facial nerve conduction within the temporal bone. The facial nerve is admitted to the temporal bone via the meatal foramen to form the labyrinthine segment of the intratemporal facial nerve. The meatal foramen in labyrinthine section of the Fallopian canal is thought to be site of constriction in Bell's Palsy based on several lines of evidence: (1) In the labyrinthine segment, the nerve occupies more than 80% of the cross-sectional area of the canal, in contrast to occupying less than 75% in the remainder (Figure 70–3); (2) The diameter of the meatal foramen (Figure 70–3A) is substantially narrower than more peripheral segments of the facial canal with a circumferential band of periosteum that virtually seals the entry site and constricts the nerve at the this site (Figure 70–4); and (3) The facial nerve is without substantial epineurium in the meatal foramen and is instead encased by this periosteum. Thus, the meatal foramen appears to constitute a pressure transition zone or “physiological bottleneck” in the presence of neural edema. The ratio of the cross-sectional areas of the nerve to the meatal foramen is significantly smaller in pediatric temporal bones compared with those of adults. This observation may explain the low incidence of Bell's palsy in pediatric populations.

In patients with near-total degeneration undergoing facial nerve decompression for Bell paralysis, electrical stimulation demonstrated a transition in responsiveness in the (decompressed) region of the meatal foramen. Sequential stimulation in a distal-to-proximal direction from the second genu to the meatal foramen consistently revealed substantially diminished responses proximal to the meatal foramen. These observations strongly implicate the meatal foramen as the primary pathophysiological site in Bell's palsy.

Intraneural inflammatory changes, consistent with a viral infection, have been identified in the temporal bones of a Bell's palsy patient who died 13 days after onset. Substantial leukocytic infiltration and demyelinization of the somatic portion of the facial nerve were evident, most prominently in the proximal, intratemporal segment of the nerve. Although small vessel congestion was present, there was no evidence of arterial thrombosis. Other studies have demonstrated that intraneural vascular congestion and hemorrhage in the labyrinthine segment of the nerve were most prominent.

Most postmortem studies from patients with Bell's palsy demonstrate that diffuse involvement of the facial nerve in its intratemporal course was typical. Evidence of an inflammatory neuritis suggesting a viral etiology is frequently evident, though not uniformly observed.

The likelihood of the meatal foramen as the critical site for nerve injury in herpes zoster oticus is supported by neuropathological findings demonstrating a sharp demarcation between the degenerated nerve distal to and normal nerve proximal to the meatal foramen.

The several postulated mechanisms of nerve injury underlying Bell's palsy are not necessarily exclusive of one another. Several pathological events may be sequential and synergistic in manifesting a clinical facial palsy, and the disease may represent a spectrum of entities with varied pathogeneses. Although inflammation and ischemia likely dominate early processes in Bell's palsy, neural blockade and degeneration as well as subsequent fibroblastic response likely manifest later in the sequence. Given the confinement of the nerve trunk within the meatal foramen, it is likely that compression at this site is a critical if not determinative event in the genesis of Bell's palsy and is triggered by one or a combination of the above etiologies. Histopathological findings suggest that the facial palsy component of herpes zoster oticus is manifest by a similar process of entrapment, with typically a higher risk of irreversible degeneration of nerve fibers.

Etiology

Viral Neuritis

There is a significant resemblance between Bell's palsy and other neuropathies known to be of viral origin. Poliomyelitis, mumps, Epstein-Barr virus, and rubella infections can manifest a neuritic component characterized by progressive neural dysfunction, often with subtotal regeneration as is often observed with Bell's palsy and herpes zoster oticus. There are multiple lines of evidence for a viral etiology in Bell's palsy based on clinical observations and experimental models reported over the last 20 years. Rabbit facial nerve trunks inoculated with herpes simplex virus demonstrate facial motor dysfunction that progressed to paralysis within the first week after inoculation. Herpes simplex virus Type I has been identified in isolates of the herpes simplex virus from the nasopharynx of patients during the acute phase of Bell's palsy. A higher prevalence of herpes simplex viral antibodies has been identified in patients with Bell's palsy as compared with gender- and age-matched controls. Herpes simplex virus has a well-known predilection for sensory neurons as well as a predilection to exist in a latent phase in sensory cell bodies of the ganglion. The facial nerve contains sensory neurons with cell bodies located in the geniculate ganglion, and it is believed that infection of the facial nerve, such as a geniculate ganglionitis, underlies Bell's palsy.

The presence of the herpes simplex virus has been detected in epineurial biopsies from a patient undergoing facial nerve decompression for Bell paralysis. While this finding further links Bell's palsy with a herpes simplex viral infection, ultrastructural studies of autopsy material from asymptomatic patients has demonstrated herpes simplex viral particles in sensory ganglia of regional cranial nerves, most notably the trigeminal ganglion. Thus, evidence of viral presence in the facial nerve, although highly suggestive, does not prove conclusively that the herpes simplex virus bears a causal role in Bell's palsy.

The role of the varicella-zoster virus as etiologic in herpes zoster oticus is supported strongly by the characteristic varicelliform rash. This rash assumes a dermatologic distribution in a pattern that mimics the distribution of afferent fibers of the facial nerve. Serological confirmation of varicella-zoster infection is often, but not always, possible. Histological studies indicate facial dysfunction with herpes zoster oticus to be the result of an entrapment neuropathy, with more pronounced nerve fiber degeneration than that typically found in histopathological studies of Bell's palsy.

The herpes simplex and varicella-zoster agents are both DNA viruses of the herpes virus group and differ subtly in their ultrastructural features. Although differences in biological behavior suggest that neuritides resulting from these viruses should manifest clinically distinguishable differences in their clinical presentation, infections from herpes simplex and varicella-zoster viruses may mimic one another. Furthermore, herpes simplex, mumps, and cytomegalovirus infections may produce a clinical picture resembling herpes zoster oticus; varicella-zoster neuritis may occur in the absence of a rash (ie, zoster sine eruptione).

Ischemic Insult

One time-honored concept of the genesis of Bell's palsy holds that impaired neural conduction follows small vessel ischemia. The facial nerve derives its blood supply from an extrinsic, circumneural vessel network derived from three principle sources: (1) the labyrinthine artery (proximally), (2) the middle meningeal artery (centrally), and (3) the stylomastoid artery (distally). The circumneural system connects to an intrinsic vascular supply of small vessel tributaries within the perineurial compartment. The pathological process is thought to involve the intrinsic system of vessels. Pressure elevations within the intraneural compartments produce venous stasis, stagnation of capillary flow, and a cycle of additional edema and an elevation in intraneural pressure. Circulatory sludging and, ultimately, tissue damage through acidosis and anoxia ensue. The mechanism by which the cascade of primary ischemia is initiated remains unclear.

Immunologic Injury

Several investigations have implicated immunologic injury as a potential cofactor in Bell's palsy. Neuropathological findings of segmental demyelinization accompanied by lymphocytic infiltration of the perineurium support this etiology. Autoimmune mechanisms of nerve injury have also been suggested; evidence for humoral and cellular autoimmunity has been reported. Immunoassay methods have been used to detect acute-phase antibodies within the chorda tympani nerve from three of seven patients with Bell's palsy. Immune complexes found in the chorda tympani nerve fibers were characteristic of viral–antibody (Type III) immunologic reaction, suggesting an immune injury triggered by the presence of viral antigens.

Incidence & Risk Factors

A wide spectrum of health care providers manage cases of acute facial palsy; an assessment of the true incidence of Bell's palsy is therefore complicated by this wide distribution of specialists. Nonetheless, this disorder is recognized as one of the most common neuropathies and appears to be universal in its occurrence. The incidence is approximately 15–40 per 100,000 individuals in the general population.

Age and gender influence the likelihood of contracting Bell's palsy. Bell's palsy is infrequent in patients under the age of 10 years, but thereafter increases in incidence with age. Females in their teens and twenties carry a predilection for the disorder. Among middle-aged adults, there is a nearly equal distribution by gender with a slight male predominance in older age groups. Epidemiological surveys indicate a seasonal variation in incidence in some geographic regions.

The risk posed by diabetes mellitus in developing Bell's palsy remains undetermined, although most studies suggest a heightened susceptibility. Several authors have demonstrated a correlation between pregnancy and acute facial palsy, particularly during the third trimester and with the presence of preeclampsia.

Immunodeficiency may also entail a heightened risk for acute facial palsy. Cranial neuropathies, including facial palsy, are observed with human immunodeficiency virus (HIV) infection, often in association with a symmetrical polyneuropathy. Facial dysfunction in this setting may also reflect either susceptibility to other infectious agents or the development of lymphoma. Facial palsy in association with HIV may occur in a clinical course characteristic of Bell's palsy or herpes zoster oticus. Neuropathies may appear at any stage of HIV infection: early after initial infection, as part of the chronic illness characterized by the AIDS, or with AIDS-related meningitis. Case series suggest that facial palsy in the setting of HIV infection not associated with neoplasm demonstrates patterns of spontaneous recovery that are not unlike those of the general population.

Facial palsy associated with the conditions noted above is not necessarily diagnostic of Bell's palsy. Patients should be evaluated as completely as those who do not carry these risk factors, with the notable caveat of considering the risk and benefit of radiological studies in pregnancy.

Clinical Findings

Patient Evaluation

The diagnosis of Bell's palsy is one of exclusion. Facial motor disturbance should be characterized as Bell's palsy only after the exclusion of traumatic, neoplastic, infectious, metabolic, and congenital etiologies. Strict attention to the evaluation, particularly the history and otoscopic and neurological findings, often differentiates an acute facial palsy of another origin from a true case of Bell's palsy.

On the clinical examination, the severity of the palsy should be recorded by one of the standard facial nerve grading schemes. In particular, one should assess for the ability to close the eyelid, as this will have the greatest functional significance. The presence of vesicles within the auricle or external auditory canal may reveal the diagnosis of herpes zoster oticus. Pain or numbness affecting the ear, mid-face, and tongue, as well as taste disturbances, are common.

Laboratory Findings

Blood and cerebrospinal fluid studies will only rarely differentiate a facial palsy and are largely unwarranted for most cases of Bell's palsy. For atypical cases though, one should consider Lyme titers and a search for a paraneoplastic syndrome.

Imaging Studies

Routine radiological evaluation is generally not recommended for most cases of acute facial palsy, particularly when the clinical course matches that of Bell's palsy or herpes zoster oticus. However, should the patient's recovery be incomplete over 3-months time, the palsy becomes recurrent, or associated cranial nerve deficits develop, then scans are warranted. Magnetic resonance imaging scanning with dye enhancement should include the brain, the skull base, and the temporal bone to rule out a lesion along the entire course of the facial nerve. High-resolution computed tomography (CT) scanning may be useful to define the bony detail in the course of the facial nerve within the fallopian (facial) canal.

Treatment

Pretreatment Assessment

Both pharmacological and surgical treatments are designed to reduce the likelihood of residual facial dysfunction in susceptible patients with acute facial palsies. Prior reports have documented the reasons underlying the difficulty in assessing the efficacy of steroids and other therapeutic modalities for Bell's palsy. Evaluation of the response is complicated by the potential for spontaneous remission for most acute palsies. Impediments such as the fragmentation of care of facial palsy patients, as well as the difficulty in obtaining early assessment and maintaining strict experimental conditions, have thwarted systematic, definitive studies.

In order to assess the response to treatment, patients with facial palsy should be initially stratified using clinical and electrophysiological criteria (see Chapter 69, Anatomy, Physiology, and Testing of the Facial Nerve). The assessment of the ultimate outcome requires sensitive and objective measures and a classification system that is universally accepted. As with any study of treatment effect, inconclusive or negative results may reflect insensitive measures of outcome.

A variety of facial nerve classification schemes have been proposed. The difficulty, of course, lies in translating facial impairment into a classification that is continuous and enables precise comparisons of functional recovery. Intermediate levels of recovery are particularly difficult to classify with consistency among observers. Although simplicity in the classification enhances acceptance, subtle differences in the quality of the outcome are less likely to be differentiated. Presently, the House-Brackmann grading system has been adopted by the American Academy of Otolaryngology-Head and Neck Surgery and has found the greatest acceptance among otolaryngologists in the United States (Table 70–3).

Steroid Therapy

Most early studies of the value of steroids in treating Bell's palsy were based on comparisons of treated patients with retrospective controls. While double-blinded, randomized, controlled clinical trials have demonstrated a significantly higher rate of complete functional recovery in glucocorticoid-treated patients in comparison to the control group in most studies, the lack of randomization and concurrent controls and the dose of glucocorticoid utilized have not completely resolved the question.

Some double-blinded trials have demonstrated beneficial effects of glucocorticoid therapy as long as therapy was initiated early in the course of the palsy.

Meta-analytic reviews of steroids in the treatment of Bell's palsy suggest that they may have the following effects: (1) reducing the risk of denervation if initiated early on, (2) preventing or lessening synkinesis, (3) preventing progression of incomplete to complete paralysis, (4) hastening recovery, and (5) preventing autonomic synkinesis (crocodile tearing). Together, these studies point to the effectiveness of steroids, particularly if given early in the course of disease. From a practical standpoint, in light of the low risk of side effects and minimal costs involved, prednisone is commonly started at the initial visit—even in patients with partial palsy—on the chance that a complete palsy might evolve within a few days. The initiation of steroid therapy during the first 24 hours of symptoms might confer a higher likelihood of recovery. In patients with Ramsay Hunt syndrome, higher rates of full recovery have been noted by some studies for patients receiving intravenous therapy.

Glucocorticoid Steroids

Glucocorticoid steroids exert an inhibitory effect on virtually every phase of the inflammatory response and thus have assumed an important role in treating a vast range of inflammatory and immune-mediated disorders. The precise mechanism by which steroids exert beneficial effects is incompletely defined in many of the conditions for which they are prescribed. In many cases, guidelines and indications for steroid treatment are empiric. Such guidelines apply to the use of steroids in the treatment of Bell's palsy, herpes zoster oticus, and other facial palsies. Nonetheless, the pharmacological effects of steroids make them attractive agents for ameliorating symptoms associated with the acute phases of Bell's palsy and herpes zoster oticus, improving the likelihood of full recovery. In addition to their anti-inflammatory properties, the glucocorticoid steroids also exert a facilitatory action on the neuromuscular junction. These combined effects may contribute to the recovery of neuromusculature function in disorders such as inflammatory polyradiculoneuropathies (the Landry-Guillain-Barré syndrome), the pathology of which is marked by inflammatory, segmental demyelinization.

The desired goal of glucocorticoid therapy for acute facial paralysis is to induce effective anti-inflammatory control. In order to provide such control, the inflammatory process should be countered with consistent, pharmacological levels of an anti-inflammatory agent, beginning as soon as possible. Once the inflammatory process is checked and the stimulus for inflammation removed, therapy can be discontinued. However, abrupt withdrawal may be followed by a rebound of disease activity. To prevent reacceleration of the inflammatory process, a tapered withdrawal of the daily glucocorticoid dose over 10–14 days is recommended.

Based on the theoretical active phase of the herpes simplex and varicella-zoster viruses (3 and 14 days, respectively), the following strategy for steroid treatment of Bell's palsy and herpes zoster oticus has been proposed: oral prednisone (1 mg/kg/d) divided into 3 doses per day for 7–10 days. The daily dose should then be tapered to zero over the following 10 days. Theoretically, this dosing regimen maximizes anti-inflammatory activity while minimizing side effects and is consistent with anti-inflammatory schedules that are effective in controlling acute hypersensitivity as well as autoimmune and other inflammatory disorders.

When administered intravenously, methylprednisolone is prescribed at 1 g/d administered intravenously as either a single dose or in 3 divided doses for 3–7 days, followed by an oral prednisone taper.

Side Effects of Steroid Therapy

Side effects that are likely to be manifest during short-term steroid treatment include hyperglycemic action. Given the high incidence of glucose intolerance in some series of acute facial palsy patients, steroids should be initially prescribed with caution. Other acute side effects include CNS changes such as psychotic breaks, fluid and electrolyte disturbances, acne, increased intraocular pressure, and gastrointestinal irritation. Corticosteroids are category C drugs in pregnant patients.

An adverse effect of glucocorticoid administration that deserves special consideration is a heightened susceptibility to infection. Glucocorticoids should be used with caution in patients with existing GI infections and in cases of latent tuberculosis. The effects of glucocorticoids on cellular and humoral components of inflammation may lessen host immunity to bacterial, viral, and fungal infections. Latent infections may become reactivated and spread. Moreover, suppression of the inflammatory response may conceal symptoms and signs of infection.

While effects on host resistance have been demonstrated in experimental trials, typical daily doses of glucocorticoids (1 mg/kg/d of prednisone or its equivalent) given for 2 weeks or less are only rarely associated with an increased susceptibility to infection. The risk of steroid-induced dissemination of viruses presents a particular concern in treating acute facial palsies of viral origin. The risk of virus dissemination is significant with steroid therapy beyond 1 month and in immunosuppressed patients. Otherwise, clinical experience suggests that the risk of this complication is minimal and that steroids can ameliorate postherpetic neuralgia.

Antiviral Therapy

Antiviral therapy represents a newer adjunct in treating acute facial palsy of viral origin. A number of meta-analyses have now examined the role for antiviral therapy in patients with Bell's palsy. These studies have predominantly looked at the use of oral steroids with or without the addition of antiviral therapy, in an attempt to discern if there is incremental benefit to the antiviral therapy. While most of these studies demonstrated clear benefit with oral steroids, none has shown convincing evidence of benefit with the addition of antiviral treatment.

In contrast, antiviral therapy is a standard part of treatment for herpes zoster oticus. In cell culture, acyclovir inhibits the herpes simplex Types I and II, varicella-zoster, and Epstein-Barr viruses and cytomegalovirus.

Indications for the use of acyclovir include genital herpes, herpes simplex encephalitis, and varicella-zoster infections in immunocompromised patients. Early reports suggest that acyclovir may mitigate neurological deficits produced by herpes zoster oticus.

Intravenous Antiviral Agents

Intravenous acyclovir (10 mg/kg every 8 hours for 7 days) produced substantially greater functional return in patients treated within the first 72 hours after the onset of paralysis. Moreover, preliminary reports have demonstrated early recovery of facial nerve function and reversal of sensorineural hearing loss associated with herpes zoster oticus in response to the drug early on, though these are nonrandomized trials.

Oral Antiviral Agents

Oral antiviral agents are significantly less costly and more convenient than intravenous agents. An exception to the general preference for oral antiviral agents exists in immunocompromised patients with severe or widespread herpes zoster oticus. Newer antiviral drugs, including valacyclovir, famciclovir, and penciclovir, are better absorbed after oral administration than acyclovir and have increasingly been used in treating Ramsay Hunt syndrome. However, these drugs are more expensive than acyclovir. Valacyclovir may be superior to acyclovir in limiting zoster pain.

Acyclovir has also been used for the treatment of Bell's palsy. When compared with patients who received oral prednisone alone, some studies have identified a higher recovery rate as well as reduced rates of synkinesis in Bell's palsy patients given oral acyclovir plus prednisone, but these findings have not been born out in larger meta-analyses, as conflicting studies have found little benefit from adding oral acyclovir to prednisone in Bell's palsy.

Synthesizing the myriad clinical trials on the topic, one can say that oral acyclovir appears reasonably indicated in all cases of herpes zoster oticus. Although proof of efficacy is limited in Bell's palsy, low risks and costs associated with acyclovir suggests that it may be reasonable to include its use in patients with complete facial paralysis. Acyclovir is prescribed at 400 or 800 mg five times daily and administered orally for 7–10 days in Bell's palsy. Alternately, acyclovir may be prescribed at 300–1000 mg (5–10 mg/kg) three times daily administered intravenously. Higher acyclovir doses (ie, 4000 mg/day orally) are recommended for patients suffering from herpes zoster oticus. Intravenous dosing is often indicated for immunocompromised individuals with severe infection. The main side effects of antiviral agents are nausea, malaise, injection site reactions, and mild renal insufficiency. Acyclovir is a category B drug in pregnant patients.

Physical Therapy

Electrical Stimulation

Transcutaneous electrical (galvanic) stimulation of the facial muscles has been used in an effort to maintain membrane conductivity and reduce muscle atrophy. It has also been used to potentially limit residua such as persistent paresis in patients with longstanding facial palsy. There exist few compelling, comparative trials to support this practice, although interest in this measure persists. Electrical stimulation may also improve function in chronic facial palsy. Patients left with partial deficits often benefit from physical therapy. Electromyographic and mirror feedback has been used to facilitate muscle reeducation to assist in the recovery of symmetric facial tone and expression.

Eye Care

The cornea is vulnerable to drying and foreign body irritation in acute facial palsy due to orbicularis oculi dysfunction. Corneal desiccation and abrasion can result from incidental contact, particularly during sleep, and can progress to cataract formation. Measures that confer corneal protection are recommended. Examination of the cornea by slit lamp biomicroscopy and either fluorescein or rose bengal staining provides the most sensitive measure for the early detection of corneal compromise. For mild facial paresis, therapy is generally not needed, unless dysfunction of cranial nerve V is present because the combination of a facial weakness and dysesthesia dramatically increases the risk of corneal exposure and ulceration. For moderate-to-severe deficits, a corneal moistening regimen should consist of a moisture chamber, artificial tears during the daytime, and ocular ointments at night. Sunglasses or other protective eyewear should be worn to protect the eyes in the outdoors. The lower eyelid can be gently elevated with adhesive tape running obliquely from the lower lid to the orbital rim, temporarily improving lid closure.

In longer standing cases of facial palsy, lubrication and occlusion are insufficient to protect the cornea. Implanting a gold weight in the upper lid, which will induce ptosis, and reducing the exposed area of cornea may augment lid suturing. This procedure is often augmented by elevating the lower lid via a lateral canthopexy, in which the tarsal ligament is suspended to the periorbital periosteum. Joining the upper and lower lid margins laterally (tarsorrhaphy) may be performed to narrow the palpebral fissure. The standard procedure calls for suturing a margin of upper and lower lid together from the lateral canthus inward. The width of the tarsorrhaphy is adjusted to optimize the degree of lid closure. If neural recovery ensues, the tarsorrhaphy can be reversed.

Surgical Measures

Mounting anatomic and electrophysiological evidence of a specific anatomic lesion site in Bell's palsy has guided the choice of procedures for surgical intervention. These approaches now focus on decompressing the meatal foramen and adjacent labyrinthine segment of the nerve for cases thought to have a poor prognosis for complete recovery with medical treatment alone.

Nerve Decompression

Surgical approaches to treating acute facial palsy are based on the premise that axonal ischemia can be reduced by the decompression of nerve segments presumed to be inflamed and entrapped. Facial nerve decompression, aimed at alleviating Bell's palsy and herpes zoster oticus, has been variably embraced for more than 70 years. The roll of surgery has evolved in concert with developments in electrophysiological testing and techniques of enhanced surgical exposure of the facial nerve.

Preoperative Considerations

Evoked electromyography (EEMG) may be used to help stratify patients who might benefit from facial nerve decompression. Surgical treatment is offered when evoked response amplitudes are 10% (or less) of the normal side. This criterion is based on the observation that approximately half of patients who progressed to a nadir of 95–100% degeneration within 2 week of the onset of the paralysis demonstrated a permanent, unsatisfactory recovery of facial function. Furthermore, most patients who reach a 90% level of degeneration progressed beyond 94% degeneration in the EEMG profile. Therefore, the proposal that immediate surgical decompression be performed as soon as the 90% level of degeneration has been reached entailed unnecessary surgery in, at most, 10% of patients. All patients who underwent decompression when degeneration reached 90% demonstrated a satisfactory return of facial movement. The 90% rate of satisfactory outcome with surgery compared favorably with the 50% chance of satisfactory return noted in patients who were not operated on and who were matched by EEMG profile. Surgery performed on eight patients in the third week after the onset of the palsy, when degeneration exceeded 90%, did not significantly improve the return of facial function. However, two patients in this group demonstrated an exceptional return of facial movement after decompression. These observations suggest that studies of more patients with delayed degeneration are needed before the role of surgical decompression can be assessed definitively in this subset of patients.

Transmastoid Approach

Both transmastoid and middle fossa approaches have been described, though transmastoid approaches are thought to provide limited exposure of the meatal foramen due to the interposed labyrinth. The transmastoid approach to the geniculate ganglion and the labyrinthine segment obviates a craniotomy, but requires removal of the incus in poorly pneumatized bones to facilitate exposure of the facial nerve proximal to the cochleariform process. Some studies have shown that facial nerve decompression using the transmastoid approach improved recovery in patients whose maximal nerve stimulation responses were reduced by 75% or more. However, long-term follow-up of these patients failed to evidence significant benefit from this procedure as compared with the spontaneous recovery rate found in other studies.

Middle Cranial Fossa Approach

The middle cranial fossa approach to the meatal, labyrinthine, and geniculate segments of the nerve facilitates direct decompression with small though significant risk to the labyrinth (Figure 70–5A). Permanent ipsilateral auditory and vestibular loss, meningitis, and subarachnoid hemorrhage are potential complications of facial nerve decompression via a middle cranial fossa approach. This approach also permits direct stimulation of the facial nerve proximal to the meatal foramen, enabling verification of the site of impairment if a complete loss of response to electrical stimulation has not yet occurred. Intraoperative stimulus trials typically reveal severely decreased to absent responses proximal to the foramen. However, stimulation distal to the foramen typically evokes potentials of substantially greater amplification (Figure 70–5B).

Nerve Grafting

Facial motor reinnervation may be accomplished by either grafting a section of normal peripheral nerve over a damaged area, bringing fibers from the intact facial nerve across the midline to innervate the paralyzed side, or by direct anastomosis of the ipsilateral hypoglossal nerve with the peripheral facial nerve. Nerve grafting may be augmented by muscle transfer procedures, since atrophy of facial muscles may render the muscle fibers less amenable to reinnervation. A wide variety of reconstructive procedures including rhytidectomy, blepharoplasty, brow lift, and fascial slings can improve resting tone and symmetry.

Aberrant regeneration may give rise to inappropriate patterns of reinnervation wherein specific muscle groups receive excessive neural inputs. Spasm and synkinesis with facial nerve recovery often produce undesired eye closure (Figure 70–6). This form of aberrant facial nerve regeneration can often be managed with subcutaneous or intramuscular botulinum toxin injections. Botulinum toxin, which induces temporary paresis in targeted muscles for up to 6 months, can reduce disability with tonic contractions, hemifacial spasm, and synkinesis. Side effects of botulinum toxin are rare and typically reveal severely decreased to absent responses proximal to the foramen. However, stimulation distal to the foramen typically evokes potentials of substantially greater amplification.

Prognosis

Most series that have assessed surgical decompression of the facial nerve in Bell's palsy have been small and retrospective and have targeted subjects most likely to suffer residual deficits (ie, patients with complete palsies and severe reductions in neural conductivity as demonstrated by electrophysiological testing). No surgical series has been randomized and several studies have shown no benefit, though these studies all utilized a transmastoid approach to decompression. Results that have employed the middle fossa approach have included multicenter, prospective data, though subjects were nonrandomized. In these studies, patients recovered completely or with slight residual deficits in 91% of the surgical group, but in only 42% of a similar, medically treated group, suggesting a benefit of decompression using this surgical approach. Because of the difficult nature of designing such a controlled trial, the precise role of facial nerve decompression in the management of Bell's palsy and herpes zoster oticus remains unclear at present.

Other Facial Nerve Disorders

Next to Bell's palsy, the most common causes of acute, peripheral facial paralysis are trauma, herpes zoster oticus, bacterial infection, perinatal factors, and neoplastic involvement of the nerve. An acute facial palsy due to trauma or infection often presents with characteristic findings that readily point to a diagnosis. In contrast, differentiating neoplastic involvement of the facial nerve from Bell's palsy frequently poses a dilemma. Several other disorders (described below) should be considered in the clinical evaluation of an acute facial palsy. It must always be remembered that Bell's palsy is a diagnosis of exclusion, and one should therefore consider the following disorders in the context of the presenting symptoms and signs of the patient.

Facial Nerve Neoplasms

A variety of neoplasms may induce a facial palsy, which is occasionally acute in onset (see Table 70–1 and Figure 70–7). It is estimated that there is an incidence of sudden facial palsy in 27% of patients found to have neoplastic involvement of the nerve—a surprisingly high incidence given the slow growth and encapsulation of most tumors responsible for the palsy.

While Bell's palsy may present with a variety of associated symptoms, atypical presentations warrant consideration of other etiologies, particularly neoplasms. A facial palsy produced by a neoplasm may differ only subtly from Bell's palsy. There are characteristic historical and clinical features that suggest that a neoplasm is responsible for a facial palsy and necessitate further evaluation (Table 70–4).

Although Bell's palsy may recur, a recurrent palsy indicates the need for an exhaustive tumor search with radiological evaluation of exploratory surgery, which is performed rarely. A neoplasm, most frequently a facial neuroma, has been identified in 9% of patients who underwent surgery for recurrent facial palsy. When the diagnosis of a neoplasm is delayed or missed, the neoplasm carries the potential consequences of extension into the labyrinth and cranial fossae. Extension into the cerebellopontine angle diminishes the opportunity for effective reanimation with direct neural anastomosis, underscoring both the need for vigilance in cases of atypical facial palsy and the importance of early diagnosis.

Facial nerve hemangiomas may also present with facial palsy. A classic presentation of a patient with a facial nerve hemangioma is one of recurrent and progressively more severe episodes of unilateral facial palsy. Treatment involves surgical excision, often at the expense of residual facial nerve function.

Melkersson-Rosenthal Syndrome

General Considerations

Melkersson-Rosenthal syndrome represents a constellation of facial anomalies that include unilateral facial palsy, episodic or progressive facial edema, and lingua plicata (scrotal tongue). The syndrome is usually sporadic in occurrence, although familial occurrence has been described.

Pathogenesis

Although the pathophysiological basis for Melkersson-Rosenthal syndrome is uncertain, granulomatous changes have been evident in biopsies of edematous tissues in cases with chronic edema. A purely inflammatory basis for the syndrome is therefore doubtful. The syndrome thus may reflect a more generalized autonomic dysfunction that manifests as vasomotor instability. Further support for this assertion comes from the association of Melkersson-Rosenthal syndrome with migraine headaches and megacolon.

Clinical Findings

Patients may show oligosymptomatic (two of three symptoms) forms of the syndrome. Lingua plicata is most likely to occur early in life, whereas facial edema generally occurs after the initial episode of facial weakness (Figures 70–8 and 70–9). Facial dysfunction may be heralded by the onset of a facial swelling, but more typically precedes the swelling by months or years.

Episodes of facial paresis or paralysis typically begin in childhood or adolescence. Edema of the lips and palatal mucosa produces a ruddy appearance. Swelling often extends to the cheeks, eyelids, nose, and chin and may be dramatic. Progressive disfigurement can result from recurrent facial swelling. Facial weakness assumes a peripheral distribution and can be differentiated from Bell's palsy only when other manifestations of the syndrome are apparent or noted on the history. While a relapsing course is usual, good to excellent recovery is typical. However, cases of progressive dysfunction have been described.

Treatment

The treatment of facial palsy associated with Melkersson-Rosenthal syndrome is empiric. Anti-inflammatory (steroid) therapy has been employed. Reports of surgical decompression of the meatal and labyrinthine segments suggest a benefit in preventing further recurrence of the palsy.

Lyme Disease

General Considerations

Lyme disease is a multisystem infection induced by the tick-borne strain of the Borrelia burgdorferi spirochete. The occurrence of acute facial palsy in association with Lyme disease is well recognized. Unilateral or bilateral facial palsy may occur in up to 11% of patients with Lyme disease. The ratio of unilateral to bilateral involvement is 3:1.

Clinical Findings

Symptoms and Signs

While the majority of patients with facial palsy associated with Lyme disease note an antecedent rash adjacent to the site of a tick bite, others may not; the palsy may be the presenting sign of the illness. The interval between the onset of the rash and facial palsy is less than 2 months. Facial palsy may occur in association with other neurological deficits produced by meningoencephalitis and radiculoneuritis.

Following a tick bite and a 1- to 4-week incubation period, skin lesions develop in approximately 50% of infected individuals in association with flu-like symptoms. Less than half of patients suspected to have Lyme disease can recall a previous tick bite. Within weeks to months after the initial infection, constitutional, neurological, and cardiac manifestations, including ipsilateral or bilateral facial palsy, may appear. Arthritic symptoms typically follow.

Laboratory Findings

If Lyme disease is suspected, diagnostic testing should include serological testing with ELISA (Enzyme-Linked ImmunoSorbent Assay) to search for IgG and IgM antibodies. By some reports, serological evidence of Lyme disease has been found in up to 20% of patients diagnosed with Bell's palsy.

Treatment

Early antibiotic treatment is thought to enhance symptomatic improvement and prevent long-term sequelae. A 3-week course of either tetracycline (for adults) or penicillin (for children) is recommended, with erythromycin administered as an alternative choice. Adequate antibiosis provides high rates of recovery of facial function with a generally good prognosis for facial nerve recovery. Residual dysfunction was more likely in patients with bilateral involvement.

Acute Otitis Media & Mastoiditis

Clinical Findings

If the history or physical examination suggests evidence of prior or existing otitis media, or if there is a history of prior otologic surgery, an otogenic etiology should be suspected (Figure 70–10). Concomitant symptoms of hearing loss, otorrhea, and vestibular symptoms are highly suggestive of an otogenic etiology. Facial palsy due to acute suppurative otitis media is typically seen in children who appear toxic and manifest otoscopic findings of middle ear empyema. The palsy is often progressive over a 2- to 3-day interval. In such cases, there is often a history of recent episodes of otitis media that have been partially treated. In cases of prolonged palsy, radiographic evaluation of the temporal bone may rarely disclose coalescence of infection in the mastoid. Facial palsy associated with acute suppurative otitis media is generally the result of toxic neuritis and can be adequately treated with wide myringotomy and systemic antibiotics.

Treatment

Cortical mastoidectomy is required when antibiotics and myringotomy fail to render the patient afebrile after 24 hours, or when facial paralysis persists beyond 1 week. The surgical objective is to drain the empyema; extended nerve decompression is unnecessary except in cases of prolonged dysfunction.

Chronic Otitis Media

Chronic suppurative otitis media, manifesting mucosal inflammation or cholesteatoma, may produce an associated facial palsy (Figure 70–11; also see Figure 70–10). Facial nerve dysfunction associated with chronic suppurative otitis media reflects a toxic neuritis, external compression, or intraneural compression from edema or abscess.

Facial palsy associated with this disorder should be addressed surgically as soon as possible. Surgical removal of irreversible disease in the middle ear and mastoid, as well as decompression of the involved segment of the nerve without slitting the sheath, is advised. Longstanding paralysis (but less than 2 years in duration) requires sectioning of attenuated tympanic or mastoid segments of the nerve followed by grafting.

Necrotizing (Malignant) Otitis Externa

Clinical Findings

Infection by Pseudomonas aeruginosa is the primary offending agent in necrotizing infection of the external auditory canal and temporal bone. These infections are observed in patients with diabetes mellitus or in others who are immunocompromised. Patients typically present with symptoms of otorrhea and progressive, disabling otalgia. The pathognomonic signs are otoscopic evidence of ear canal inflammation or a breech of the external canal skin at the bony-cartilaginous junction. The breech is filled with granulation tissue. Facial palsy is ominous and reflects skull base extension of the osteomyelitic process along vascular channels. The diagnosis is based on the clinical presentation in association with radioisotope gallium and technetium scanning that demonstrates osteomyelitis of the temporal bone.

Treatment

Treatment of necrotizing otitis externa requires aggressive management with intravenously administered antipseudomonal antibiotics, which should be maintained for 8–12 week to facilitate sequestration of the infection. Aggressive debridement of granulation tissue within the ear canal is key to promoting the replacement of necrotic bone with viable tissue. Because necrotizing otitis externa is associated with extensive ischemia of the skull base, the operative debridement of the tympanic bone, the mastoid, and the skull base is indicated only when medical treatment fails to improve. Radioisotope scanning can be helpful while following the progress of the infection and helps to determine the length of the course of intravenous therapy that is required.

Childhood Facial Palsy

General Considerations

The evaluation of a facial palsy in a child should be guided by the fact that although Bell's palsy is the most common etiology for childhood facial palsies, it accounts for a substantially smaller proportion of palsies relative to adults. For instance, a clinically or radiographically identified etiology can be found in 20% of adult palsies initially diagnosed as Bell's palsy; this incidence may reach as high as 72% in childhood palsies. Patients under the age of 18 years with facial palsy are most likely to have an etiology of Bell's palsy (42%), trauma (21%), infection (13%), congenital causes (8%), and neoplasms (2%).

Clinical Findings

The onset of facial palsy in childhood is frequently obscured by the excellent tone of aponeurotic tissues and skin and, therefore, the excellent static suspension of central and lower portions of the face. Consequently, childhood facial nerve disorders are often referred to as “asymmetric crying facies” (see Figure 70–8).

Treatment

The treatment for childhood facial palsies generally follows that for adults.

Perinatal Facial Palsy

Traumatic Perinatal Facial Palsy

Intrauterine trauma to the facial nerve may occur as a consequence of compression from the maternal sacrum. Prolonged labor and forceps delivery may produce facial nerve trauma. The extratemporal facial nerve is at risk because the absence of an overlying mastoid tip places the vertical segment of the nerve at risk for injury. A traumatic cause of the facial nerve dysfunction is suggested by hemotympanum, periauricular ecchymosis, and the progressive decline of facial nerve responsiveness to an applied stimulus.

The assessment of perinatal facial nerve dysfunction relies heavily on electrodiagnosis. Electromyographic evidence of preserved or declining neuromuscular activity is most diagnostic. In the absence of such activity, muscle biopsy may be required to determine whether a congenital palsy exists.

A review of the etiologic basis for facial palsy in 95 newborns indicated that a traumatic etiology was suspected in 74 cases (78%), as suggested by signs of periauricular injury or electrical testing (evoked and spontaneous electromyography). There was excellent recovery in 41 of 45 children with perinatal trauma. Occasional cases of poor recovery, however, suggest the need for a radiographic and electrodiagnostic evaluation in order to detect an unfavorable prognosis for spontaneous recovery. In such cases, surgical exploration and decompression of the nerve may be critical for effective reanimation.

Congenital Perinatal Facial Palsy

Newborn facial palsy unrelated to trauma accounts for a smaller proportion of cases than does traumatic facial palsy. Both syndromic and nonsyndromic forms of congenital facial palsy occur. The palsy may be complete or incomplete, unilateral or bilateral, and isolated to particular branches. Associated craniofacial malformations, often those involving first and second branchial arch derivatives, are common. Microtia and facial clefts are most frequently noted. Palsies isolated to a single branch, particularly the marginal mandibularis, indicate the need for a cardiac evaluation in light of a high rate of concurrent cardiac conductive and anatomic anomalies.

Otologic, electrodiagnostic, and radiological evaluations are performed, as necessary, to determine the etiology. A congenital neuromuscular etiology is suggested by a concomitant defect (or defects) involving other cranial nerves and the absence of evidence of electrical responsiveness to evoked and spontaneous electromyographic evaluation.

The Möbius syndrome encompasses a wide spectrum of anomalies due to dysgenesis at the level of the brain stem with resultant neuromuscular deficits peripherally. The bilateral absence of facial and abducens nerve function, as well as other cranial neuropathies, may occur. The auditory brainstem response is often abnormal and is a helpful adjunct in diagnosis.

The prognosis for effective facial animation with congenital facial palsies is poor. However, resting tone may provide adequate eye coverage and oral competence even into adulthood. Facial motor rehabilitative procedures and reconstructive procedures to affect better symmetry may be indicated later in life.