Bell's Palsy

Reich, Stephen G. MD, FAAN

doi: 10.1212/CON.0000000000000447
Review Articles

ABSTRACT: Purpose of Review: Bell’s palsy is a common outpatient problem, and while the diagnosis is usually straightforward, a number of diagnostic pitfalls can occur, and a lengthy differential diagnosis exists. Recognition and management of Bell’s palsy relies on knowledge of the anatomy and function of the various motor and nonmotor components of the facial nerve. Avoiding diagnostic pitfalls relies on recognizing red flags or features atypical for Bell’s palsy, suggesting an alternative cause of peripheral facial palsy.

Recent Findings: The first American Academy of Neurology (AAN) evidence-based review on the treatment of Bell’s palsy in 2001 concluded that corticosteroids were probably effective and that the antiviral acyclovir was possibly effective in increasing the likelihood of a complete recovery from Bell’s palsy. Subsequent studies led to a revision of these recommendations in the 2012 evidence-based review, concluding that corticosteroids, when used shortly after the onset of Bell’s palsy, were “highly likely” to increase the probability of recovery of facial weakness and should be offered; the addition of an antiviral to steroids may increase the likelihood of recovery but, if so, only by a very modest effect.

Summary: Bell’s palsy is characterized by the spontaneous acute onset of unilateral peripheral facial paresis or palsy in isolation, meaning that no features from the history, neurologic examination, or head and neck examination suggest a specific or alternative cause. In this setting, no further testing is necessary. Even without treatment, the outcome of Bell’s palsy is favorable, but treatment with corticosteroids significantly increases the likelihood of improvement.

Address correspondence to Dr Stephen G. Reich, University of Maryland School of Medicine, 110 S Paca St, 3rd Floor, Baltimore, MD 21201,

Relationship Disclosure: Dr Reich serves as associate editor of the Journal of Clinical Movement Disorders and on the editorial board of Parkinsonism & Related Disorders. Dr Reich has received publishing royalties from Informa, has received research support as an investigator for studies from the National Institute of Neurological Disorders and Stroke, and has given expert medical testimony in legal cases related to malpractice.

Unlabeled Use of Products/Investigational Use Disclosure: Dr Reich discusses the use of acyclovir and valacyclovir for the treatment of Bell’s palsy.

Supplemental digital content: Videos accompanying this article are cited in the text as Supplemental Digital Content. Videos may be accessed by clicking on links provided in the HTML, PDF, and app versions of this article; the URLs are included in the print version. Video legends begin on page 464.

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Bell’s palsy is a common outpatient problem, and while the diagnosis is usually straightforward, a long and broad differential diagnosis exists for peripheral facial nerve palsy, and approximately one-third of cases are due to another cause. Bell’s palsy is characterized by the acute spontaneous onset (72 hours or fewer) of unilateral peripheral facial paresis or palsy in isolation (no other neurologic or systemic signs), for which no specific etiology is uncovered, and in almost all cases, shows improvement within several months.1 If a specific cause is found, such as Lyme disease or sarcoidosis, it should not be referred to as Bell’s palsy.

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Sir Charles Bell (1774 to 1842) is associated with idiopathic peripheral facial palsy, not because he was the first to observe or report this finding, since depictions of facial palsy can be traced to ancient art and texts (Figure 5-1),2 but instead because Bell recognized that peripheral facial palsy resulted from involvement of the seventh cranial nerve (which he referred to as the respiratory nerve). As he demonstrated in a series of clinical and experimental observations, the seventh cranial nerve controlled the muscles of facial expression, as stated by Bell:

On cutting the respiratory nerve on one side of the face of a monkey, the very peculiar activity of his features on that side ceased altogether. The timid motions of his eye-lids and eyebrows were lost, and he could not wink on that side; and his lips were drawn to the other side, like a paralytic drunkard, whenever he showed his teeth in rage…the conclusion is inevitable, that the motions of the lips, nostrils and eye-lids, and forehead, in expression, have nothing to do with the fifth pair of nerves… A man had the trunk of the respiratory nerve of the face injured by a suppuration, which took place anterior to the ear, and through which the nerve passed in its course to the face. It was observed, that in smiling and laughing, his mouth was drawn in a very remarkable manner to the opposite side. The attempt to whistle was attended with a ludicrous distortion of the lips: when he took snuff and sneezed, the side where the suppuration had affected the nerve remained placid, while the opposite side exhibited the usual distortion.3

Bell was born in Edinburgh, Scotland, and trained as a surgeon, but he is best recognized for his contributions as an anatomist. He was also an accomplished artist who illustrated many of his own dissections. In 1804 Bell moved to London, where he helped found medical schools at University College London and Middlesex. Prior to his discovery of the innervation of the face, Bell demonstrated that the ventral spinal root is motor; the Bell-Magendie law attributed motor and sensory functions to the ventral and dorsal roots, respectively. In addition to Bell’s palsy and the Bell-Magendie law, he is also eponymized by Bell’s phenomenon (upward deviation of the eyeball during forced closure of the lids) and by the long thoracic nerve of Bell that innervates the serratus anterior.4–6

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When evaluating a patient with a peripheral facial palsy, the most clinically relevant anatomic facts to appreciate are the following:

* A peripheral (lower motor neuron) facial palsy weakens the entire ipsilateral face, including the frontalis and orbicularis oculi muscles, which are spared with central (upper motor neuron) lesions that cause weakness of only the lower two-thirds of the contralateral face (Figure 5-2). The features of a peripheral facial palsy were beautifully described by Romberg7: “The patient is unable to corrugate his forehead, the furrows on which disappear at once with the paralysis, so that the brow of an old man becomes as smooth as that of a child, and no more effectual cosmetic is to be found for elderly ladies.” Therefore, a helpful clinical pearl for differentiating a central versus peripheral facial palsy is that the latter “gets out the wrinkles.” Of course, this is not clinically useful in the young, unwrinkled patient.

* It is distinctly rare to have a parenchymal lesion affect the facial nucleus or fascicle in isolation. The clue that a peripheral facial palsy is from a central lesion is the presence of neighborhood signs localizing to the pons. These include an ipsilateral horizontal gaze palsy due to involvement of the paramedian pontine reticular formation; ipsilateral sixth nerve palsy; internuclear ophthalmoplegia (INO) due to involvement of the ipsilateral medial longitudinal fasciculus; ipsilateral facial numbness due to involvement of the descending tract of cranial nerve V; and a contralateral hemiparesis. The combination of a peripheral seventh cranial nerve palsy along with an ipsilateral horizontal gaze palsy and INO is known as the eight-and-a-half syndrome, adding the seventh nerve palsy to the more well-known one-and-a-half syndrome.8

* The facial nerve innervates more than just the muscles of facial expression. Afferent fibers convey sensation from the external auditory canal, pinna, mastoid, and mucosa of the palate (hence the need to check the palate as well as the auditory canal for vesicles in suspected geniculate zoster/Ramsay Hunt syndrome) as well as taste from the anterior two-thirds of the tongue. Parasympathetic fibers in cranial nerve VII innervate the lacrimal gland and minor salivary glands. The sensory and parasympathetic fibers are carried via the nervus intermedius (Wrisberg nerve) (Figure 5-39).1,10–12

The nucleus of cranial nerve VII is in the tegmentum of the caudal pons. The fascicle ascends, looping around the abducens nucleus, protruding in the fourth ventricle as the facial colliculus before exiting the dorsolateral pons (cerebellopontine angle). The parasympathetics arise in the superior salivatory nucleus; taste fibers terminate in the nucleus of the tractus solitarius, and the sensory afferents terminate in the nucleus of the spinal tract of cranial nerve V.

The facial nerve travels with the vestibulocochlear nerve in the internal auditory meatus before entering the facial canal (fallopian canal), a narrow bony canal within the temporal bone. It is because of its course through this narrow canal, with little room for expansion, that inflammation of the nerve (due to any cause) is thought to cause compression resulting in paralysis and, as will be discussed, is the rationale for the use of corticosteroids for Bell’s palsy. The first branch of the facial nerve to exit, at the level of the geniculate ganglion, is composed of the fibers innervating the lacrimal gland, via the greater superficial petrosal nerve. If lacrimation is diminished in a peripheral facial palsy, it suggests a more proximal lesion. Distal to the geniculate ganglion, the fibers innervating the stapedius muscle exit (this explains why some patients with Bell’s palsy may have hyperacusis).

The chorda tympani is the final branch of cranial nerve VII before it exits the skull at the stylomastoid foramen. The chorda tympani, as previously mentioned, conveys taste from the anterior two-thirds of the tongue (as such, taste may be affected in Bell’s palsy and is sometimes the first symptom) and joins with the lingual nerve to innervate the minor salivary glands (their involvement is rarely evident in Bell’s palsy). From the stylomastoid foramen, the facial nerve courses through the parotid gland before dividing into branches that innervate all of the muscles of facial expression as well as the buccinator.1,10–12 It is at this level that individual branches of cranial nerve VII can be affected by infiltrative or compressive lesions, or trauma, and cause a partial lower motor neuron facial palsy with sparing of the frontalis. This is why it is important to do a careful head and neck examination in the patient with a peripheral facial palsy, with particular attention to the parotid gland, cervical adenopathy, or skin lesions, the latter relevant to perineural invasion by squamous or other types of cancer.13

Sparing of the frontalis with a “central (upper motor neuron) facial” is traditionally thought to reflect bilateral supranuclear innervation from the primary motor cortex, with the lower two-thirds of the face receiving predominantly contralateral innervation. In contrast, studies in nonhuman primates suggest that either there is little corticobulbar innervation of the VII subnuclei innervating the frontalis14 or that innervation is from cortical areas distinct from those supplying the lower two-thirds of the face.15,16 A study in humans suggests that sparing of the orbicularis oculi by upper motor neuron lesions is due to its dual innervation from cortical regions supplied by both the middle cerebral artery and anterior cerebral artery in contrast to the lower face, where cortical innervation is supplied solely by the middle cerebral artery.17

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The incidence rate of Bell’s palsy is 20 to 40 out of 100,000 per year, and sexes are equally affected with an average age of onset of 40 years. The incidence rate is highest in those age 70 years and older. No difference exists in the side of the face affected, nor does there appear to be a seasonal predominance.18,19 A number of “risk” factors have been reported for Bell’s palsy, including diabetes mellitus and hypertension, with little definitive evidence; however, both have been associated with a worse prognosis for recovery as has older age, non-ear pain, complete palsy, and decreased tearing.18–20 Although pregnancy is often cited as a risk factor for Bell’s palsy, this was not found to be the case in the epidemiologic study from Rochester, Minnesota, by Hauser and colleagues.18 In this regard, Katz and colleagues21 found that risk factors for Bell’s palsy during pregnancy included chronic hypertension, maternal obesity, and severe preeclampsia, but Bell’s palsy had no effect on perinatal outcome (Case 5-1).

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Case 5-1

A 31-year-old woman presented with a history of Bell’s palsy, which had been diagnosed 1 month before the visit when she was 32 weeks pregnant, and her pregnancy had otherwise been uncomplicated. Her first symptom had been that her taste was “funny.” The following day she had noticed “drooping” of the right face and difficulty closing the right eye. By the next day, she had complete right facial paralysis. She was seen by her obstetrician and started on prednisone and valacyclovir. About 1 week after the prednisone was stopped, she experienced 3 to 4 days of pain around the right side of her head and jaw, which she described as severe and that resolved spontaneously. The weakness had improved when she presented for neurologic consultation. On examination, the patient hadminimal asymmetry of her face at rest; while showing her teeth, no movement of the right side of the face occurred; she could barely approximate the lids when squeezing the eyes shut, and the frontalis muscle on the right was weak (Figure 5-4). She reported 80% return of function 6 months later.

Comment. The teaching points of this case include: (1) Bell’s palsy can occur during pregnancy, although it is not clear that this is an actual risk factor; (2) altered or diminished taste can be the initial symptom of Bell’s palsy; (3) pain is not an uncommon feature of Bell’s palsy, either at presentation or during recovery; and (4) regarding pregnancy, valacyclovir is category B, suggesting that it is probably safe to use during pregnancy.

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The cause of Bell’s palsy is not known and may not be the same in all individuals. Edema of the facial nerve within the narrow fallopian canal has been observed during decompressive surgery for Bell’s palsy22 consistent with MRI enhancement of the facial nerve in Bell’s palsy.23 The cause of the edema may be ischemia in predisposed patients, such as the elderly or those with diabetes mellitus or hypertension, akin to other known ischemic cranial neuropathies, including the abducens and oculomotor nerves.24 But this would not account for the many young people with Bell’s palsy, including children. Herpes simplex virus (HSV) type 1, according to Gilden,1 “is probably the cause of most cases of Bell’s palsy…[and] reflects virus reactivation from latency in the geniculate ganglion rather than primary infection.” Supporting evidence includes the isolation of HSV DNA from endoneurial fluid in Bell’s palsy25; increased salivary shedding of HSV DNA in patients versus controls26,27; polymerase chain reaction (PCR) evidence of HSV type 1 in the geniculate ganglia28,29; and an HSV type 1 experimental animal model of Bell’s palsy.30,31 Despite this evidence, Gilden1 acknowledged that “how the virus damages the facial nerve is uncertain.”32,33

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Patients with Bell’s palsy typically develop facial weakness over 1 to 2 days. They may find that toothpaste, liquids, or food leak from the affected side of the mouth, that the eyelid does not close, or that it is more difficult to speak, which leads many patients to the emergency department for fear of a stroke.

The key first step in evaluating the patient is to determine whether the facial weakness is peripheral or central. Of note is that, while almost all patients with a hemiparesis from stroke have facial weakness, it is rarely the presenting symptom and is often noticed by others rather than the patient (Case 5-2). As discussed in the section on anatomy, with a central facial palsy, sparing of the upper one-third of the contralateral face occurs. With a peripheral facial palsy, weakness of all muscles of facial expression occurs. The furrow is lost from the brow, and the patient cannot elevate the brow (ie, in response to the command, “raise your forehead like you’re surprised”), the palpebral fissure is wider, the nasolabial fold is flattened, the cheek cannot be puffed out, and the nares do not flare with a hard inspiration. The patient is unable to whistle, and when smiling or showing teeth, the mouth is drawn to the intact side. Having the patient test his or her ability to whistle is a useful way to document recovery.

Although most patients with Bell’s palsy do not notice a dry eye (recall that the lacrimal gland is innervated by cranial nerve VII), nevertheless, as discussed in the section on treatment, proper lubrication and eye care is necessary, particularly when severe weakness of the orbicularis oculi occurs to the extent that the upper and lower lids cannot be approximated. Paradoxically, some patients may present with tears running down the cheek, presumably due to weakness of the inferior portion of the orbicularis oculi, preventing tears from being directed toward the lacrimal duct, possibly in combination with ocular irritation. If the stapedius muscle is involved, hyperacusis may occur, as contraction of the stapedius functions to dampen the ossicles. Despite the facial nerve innervation of minor salivary glands, dry mouth is usually not experienced. Involvement of the chorda tympani causes loss of taste in the ipsilateral anterior two-thirds of the tongue; this can sometimes be the first symptom noticed by the patient, and impaired taste may portend a worse prognosis for recovery. Other factors reported to be associated with a worse outcome include complete facial palsy, older age, diabetes mellitus, and, as mentioned in the following section, non-ear pain.18–20

It is not uncommon for patients with Bell’s palsy to report pain—typically around the ear, mastoid, and face—and non-ear pain has been associated with a worse prognosis. Likewise, patients may report facial “numbness” (it is important to ask what they mean by numbness), but sensory testing is usually normal in Bell’s palsy. Yet, some authors have suggested that patients with Bell’s palsy in fact have a cranial polyneuropathy. Adour11 found evidence of involvement of cranial nerves V, VIII, IX, and X in patients with Bell’s palsy.34 In a series of 51 patients diagnosed with Bell’s palsy, Benatar and colleagues35 found that 8% had evidence of involvement of at least one other cranial nerve, including the trigeminal, glossopharyngeal, and hypoglossal. These findings raise several questions: is Bell’s palsy really a cranial polyneuropathy simply dominated by involvement of the facial nerve? Or, should signs of involvement of other cranial nerves “rule out” Bell’s palsy? The important point is that, in an otherwise “typical” case of Bell’s palsy, patients may have other subtle cranial nerve symptoms and signs, but their presence should be a red flag that the condition might not be Bell’s palsy, and careful follow-up is warranted.

The majority of patients with Bell’s palsy will not have a recurrence, but a recurrence happens in about 7%, either on the same or the opposite side.36–38 A recurrence should prompt a careful search for an alternative cause, such as sarcoidosis39,40 or other inflammatory or infiltrative disorders. The Melkersson-Rosenthal syndrome is another consideration for recurrent peripheral facial palsy; it is characterized by a fissured tongue and periodic lip or facial swelling,41 but many patients do not have the entire triad; inspection of the tongue can be an important clue.42

By adhering to the definition of Bell’s palsy as a spontaneous, acute, unilateral, isolated peripheral facial palsy, and if no red flags suggest an alternative cause, then neither laboratory testing nor imaging is needed43; unfortunately, the majority of patients undergo imaging. MRI of patients with Bell’s palsy may show enhancement in the intracanalicular and labyrinthine segments of the facial nerve (Case 5-2),23,44 and this should not necessarily suggest an alternative diagnosis. As pointed out by Sartoretti-Schefer and colleagues,44 the normal facial nerve may show enhancement of the geniculate ganglion and the tympanic-mastoid segment. Electrodiagnostic studies have little role in the management of Bell’s palsy.43 According to a clinical practice guideline from the American Academy of Otolaryngology—Head and Neck Surgery Foundation, based on level C evidence, electrodiagnostic studies are not recommended for patients with incomplete facial paralysis, most of whom will have a good recovery, but may be offered to the patient with complete paralysis for prognostic purposes, although it is not likely to change management.43

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Case 5-2

A 40-year-old woman presented to the emergency department after noticing that her face felt “swollen” upon awakening, and she noted that the right side of her face felt “distorted and weak.” She noticed toothpaste leaking from the right side of her mouth, tearing of the right eye, and inability to flair the right nostril.

On examination, the patient had mild right peripheral facial paresis with an otherwise normal examination. As she was initially suspected of having a stroke, she underwent an MRI, which demonstrated mild enhancement of the intracanalicular and labyrinthine segments of the right facial nerve (Figure 5-5). She was treated with eye care, corticosteroids, and valacyclovir. She had complete resolution of her symptoms by 3 months.

Comment. Recognition that this patient had a peripheral facial palsy, in isolation, would have steered the diagnosis and evaluation from a stroke and toward Bell’s palsy, obviating the need for the MRI. Nevertheless, it does confirm that enhancement of these particular segments of the facial nerve may occur in patients with Bell’s palsy.

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A very long list of causes of peripheral facial palsy exists (Table 5-1). At least 50% of peripheral facial palsies are due to Bell’s palsy, and when no red flags from the history or examination (Table 5-2) suggest an alternative diagnosis, the percentage is no doubt even higher. Most of the causes listed in Table 5-1 should not be confused with Bell’s palsy as long as one adheres to the features of Bell’s palsy previously mentioned: spontaneous, onset over 72 hours, otherwise normal neurologic and systemic examination, improvement over several months, and no red flags.

Historic red flags casting doubt on the diagnosis of Bell’s palsy as the cause of a peripheral facial palsy include gradual onset over weeks to months, concomitant vertigo or hearing loss, constitutional symptoms, cancer, human immunodeficiency virus (HIV)45,46 or risk factors for HIV, and features suggesting Lyme disease (eg, endemic area, known tick bite, skin rash).47–49 Since the majority of patients with Bell’s palsy improve within several months, the lack of any improvement or a gradual progression from facial paresis to facial palsy should both raise a red flag. About 7% of patients with Bell’s palsy will have a recurrence,37–39 but when this occurs, it should be considered a red flag, prompting an evaluation (to include imaging and a lumbar puncture) for another cause.

Some of the red flags from the neurologic examination include bilateral facial palsy,50 involvement of other cranial nerves (as mentioned previously, the physician may see subtle signs of other cranial nerve involvement in Bell’s palsy), hemiparesis, hearing loss or nystagmus, ataxia, horizontal gaze palsy, or systemic weakness. Important findings on the head and neck examination to look for include vesicles in the external canal, tympanic membrane or palate, cervical adenopathy, otitis media, parotid mass, skin cancer, fissured tongue, and facial swelling.41,42 It is important to recognize that a peripheral facial palsy may be the first sign of an evolving disorder such as neurosarcoidosis, meningeal carcinomatosis, or Guillain-Barré syndrome.51

Several specific causes of peripheral facial palsy deserve highlighting. It is the most common neurologic manifestation of Lyme disease,47–49 and this should always be considered in patients who live in an endemic area, especially if the facial palsy is bilateral or in a child. Halperin and Golightly49 determined that 25% of facial palsies during the summer months in an endemic area were due to Lyme disease, based on serology. Because no other clinical features may suggest Lyme disease before or at the time of facial palsy (eg, erythema migrans), and serologic evidence may lag behind the earliest clinical manifestations,47 the decision to treat rests largely on the physician’s index of suspicion for Lyme disease. If no symptoms or signs occur other than facial palsy, such as cranial polyneuropathy or evidence of parenchymal involvement, then a lumbar puncture is probably not indicated.48 Even without antibiotics, the prognosis of Lyme disease facial palsy is favorable,52 and therefore treatment is aimed at preventing sequelae. As pointed out by the American Academy of Neurology (AAN) Practice parameter, “no definitive data exist to establish the superiority, or lack thereof, of either oral or parenteral treatment.”53 For facial palsy presumed to be from Lyme disease, it is reasonable to use an oral agent. If no clinical or serologic evidence confirms the diagnosis of Lyme disease at presentation, then steroids may be considered in case the diagnosis is actually Bell’s palsy; according to the AAN practice parameter, although evidence is limited, a short course of steroids is not likely to be harmful when treating Lyme disease.53

Ramsay Hunt syndrome (Case 5-3) is manifested by a peripheral facial palsy with erythema and vesicles in the external auditory canal, the tympanic membrane, or the oropharynx. It is due to reactivation of varicella-zoster virus in the geniculate ganglion.54 Accompanying symptoms reflect neighborhood involvement of the vestibulocochlear nerve including vertigo, hearing loss, and tinnitus.

About 5% of patients with sarcoidosis will have neurologic involvement, and in one-half of those cases, it is the presenting sign, with a peripheral facial palsy being the most common manifestation. Neurosarcoidosis is particularly important to consider with bilateral peripheral facial palsy. The diagnosis may be challenging and requires a careful search for evidence of systemic involvement and, ideally, pathologic confirmation.39,40 Another important consideration, particularly when bilateral facial palsy occurs, is Guillain-Barré syndrome, which may evolve rapidly from facial palsy into a more classic picture with bulbar and limb weakness with areflexia, but a subtype of Guillain-Barré syndrome manifests by only bifacial weakness and distal paresthesia.51

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Case 5-3

A 76-year-old man noticed ear pain followed by weakness of the right face. He did not experience hearing loss or vertigo. On examination, he had a right peripheral facial palsy and erythema and vesicles in the right ear (Figure 5-6). He was diagnosed as having geniculate zoster, Ramsay Hunt syndrome, and was treated with corticosteroids and acyclovir.

Comment. Although the involvement of the ear by zoster was readily apparent in this patient, in others it is subtle, necessitating careful inspection of the external auditory canal and tympanic membrane as well as the oropharynx. The presence of vertigo, hearing loss, and tinnitus may accompany Ramsay Hunt syndrome and are important red flags pointing away from Bell’s palsy.

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Most patients with Bell’s palsy are worried they have had a stroke, so reassurance and education are important parts of treatment along with counseling that the prognosis is favorable for most patients, particularly those with mild or moderate facial weakness at presentation. Because of weakness of eyelid closure and the risk of corneal exposure, particularly in those with complete palsy, patients should use lubricating drops frequently during waking hours and a lubricating ointment at night. The lid can be taped closed at night or a cellophane patch can be applied with care so that no direct contact with the cornea occurs.

The use of steroids and antivirals to improve the recovery of Bell’s palsy is based on the previously mentioned observations about the possible roles of edema and HSV type 1 in the pathophysiology and etiology, respectively, in Bell’s palsy. Here the author relies primarily on the AAN evidence-based guidelines. The first guideline published in 2001 found only five published studies of sufficient rigor upon which to determine the effectiveness of corticosteroids (two Class I, two Class II, and one Class III), and none were sufficiently powered to allow for a definitive recommendation.55 By pooling the results of the Class I and II studies, coupled with the safety of a short course of steroids, the authors of this guideline concluded that: “steroids are safe and probably effective in improving facial functional outcomes in patients with Bell’s palsy” (level B recommendation).55 Even less evidence, and no Class I studies, existed upon which to base a recommendation for acyclovir, which received a level C recommendation of being safe and possibly effective. The lack of unbiased studies and a high complication rate precluded any evidence-based recommendations on surgical decompression.55

The AAN evidence-based guideline on steroids and antivirals for the treatment of Bell’s palsy was updated in 2012,56 and the revised recommendations were based largely on two Class I studies published since the original review. The first study by Sullivan and colleagues57 compared four treatment arms: prednisolone alone (25 mg twice per day for 10 days), acyclovir alone (400 mg twice per day for 10 days), a combination of prednisolone and acyclovir, and placebo in patients age 16 or older who presented within 72 hours of onset of Bell’s palsy (Figure 5-7). The primary outcome was the degree of facial weakness observed in digital photographs by three blinded reviewers, using the House-Brackmann facial nerve grading system, at 3 and 9 months. Of 551 patients who underwent randomization, outcome data were available for 496 (90%).

The other Class I study by Engström and colleagues58 was similar, but instead of acyclovir, valacyclovir (1000 mg 3 times per day for 7 days) was used. More than 800 patients between ages 18 and 75, presenting within 72 hours, were randomly assigned to prednisolone (60 mg/d for 5 days then reduced by 10 mg/d) and placebo, valacyclovir and placebo, placebo and placebo, and prednisolone and valacyclovir. The primary outcome measure was time to complete recovery (score of 100) on the Sunnybrook facial nerve grading system. Similar to the study by Sullivan and colleagues,57 those patients who received prednisolone had a significantly higher rate of recovery at all time points, including the final assessment at 1 year compared to placebo and to the combination of valacyclovir and prednisolone (Figure 5-8). The lower rates of recovery, even for the placebo-placebo group in the study by Engström and colleagues,58 were attributed to the higher sensitivity of the Sunnybrook scale for residual weakness. No significant adverse effects occurred in either study.

An editorial following the publication of these two trials by Tyler32 concluded that “antiviral therapy should not be routinely used in patients with [Bell’s palsy].” Tyler did, however, point out the potential benefit of antivirals for treatment of Ramsay Hunt syndrome.32 The AAN evidence-based review gave a level A recommendation to the use of corticosteroids for treatment of Bell’s palsy within 72 hours of onset. Continuing, they reiterated that adding an antiviral to a corticosteroid offers no significant benefit regarding facial recovery. However, they pointed out that the 95% confidence interval of the two Class I studies could not rule out a modest effect of adding an antiviral and gave a Class C rating to the combination.56 When discussing the combination with patients, despite counseling that adding an antiviral to a steroid does not offer significant benefit (when also told that a benefit, even modest at best, cannot be “ruled out”), most patients, in the author’s experience, opt to take an antiviral.

The clinical practice guidelines by the American Academy of Otolaryngology—Head and Neck Surgery Foundation, developed by specialists in a variety of related fields including neurology, made similar recommendations about the use of corticosteroids and antivirals for Bell’s palsy. They went on to address some of the other popularly touted treatments for Bell’s palsy, finding insufficient or poor-quality evidence to make any recommendations about the use of surgical decompression, acupuncture, and physical therapy to treat Bell’s palsy.43

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As the placebo arms of the previously mentioned studies demonstrate, up to 85% of patients with Bell’s palsy make a complete recovery within 1 year.57,58 Those left with facial weakness may be candidates for surgical procedures aimed at improving facial function, particularly when significant eyelid weakness occurs, with risk of exposure keratitis (this complication requires prompt ophthalmologic referral). These include implantation of a gold weight in the eyelid and other nerve or muscle transfer procedures that will not be reviewed here; patients should be referred to a surgeon experienced in these options.13,59

When residual weakness occurs in patients with Bell’s palsy, the apparent side of the weakness can be paradoxical. With an acute peripheral facial palsy, the nasolabial fold is flattened, and the palpebral fissure is widened. But with chronic weakness, a contracture may develop such that at rest, the nasolabial fold on the weak side is deeper and the palpebral fissure narrower (Case 5-4).60 The actual side of the weakness is readily apparent with movement, and synkinesia almost always occurs, confirming an old facial palsy. The author has been involved in a few cases where an old case of Bell’s palsy with contracture has been misinterpreted as new weakness on the patient’s good side of the face, leading to an erroneous diagnosis (usually stroke) and unnecessary testing before the findings are interpreted correctly and the history clarified. Patients are often unaware of residual weakness and synkinesia and may forget about having had Bell’s palsy many years earlier.

There are two types of synkinesias that develop after Bell’s palsy due to misdirection of regenerating fibers. The first is motor: with blinking, particularly if forceful, simultaneous contracture of the ipsilateral mouth or platysma occurs, and similarly, when smiling or showing teeth, contracture of the orbicular oculi and narrowing of the palpebral fissure occurs (Case 5-5). This is often asymptomatic but if patients are bothered, then botulinum toxin is the most effective treatment. Some patients go on to develop hemifacial spasm.61

Nonmotor fibers in the facial nerve may also misdirect, producing two types of synkinesias. The first is gustatory tearing in which salivation may be associated with lacrimation (so-called crocodile tears named for the myth that the crocodile either sheds a tear to attract its victim or sheds a tear as the victim is being eaten—in either case, the implication is that crocodile tears are insincere tears).

When salivation causes facial sweating, this is known as Frey syndrome or gustatory sweating, named for Lucja Frey, one of the first female Polish neurologists, whose productive career was cut tragically short by the Nazis.62 Although Frey was not the first to recognize this phenomenon, she is credited with discerning its physiology and pharmacology. Frey syndrome is encountered much more commonly after parotid surgery than Bell’s palsy (see the video from Reich and Grill62 for an example of Frey syndrome).

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Case 5-4

A 73-year-old man was seen for Parkinson disease and related a history of remote Bell’s palsy, from which he reported a good recovery. On examination, at rest (Figure 5-9A) the right nasolabial fold was flatter, and the palpebral fissure was wider, suggesting that was the side of the facial weakness. However, as Figures 5-9B and 5-9C demonstrate, he had a contracture on the left, which is the side of the weakness.

Comment. This case demonstrates that it can be easy to mistake the side of weakness from a previous case of Bell’s palsy, but the synkinesia is a sure giveaway.

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Bell’s palsy is characterized by the spontaneous, acute (over 24 to 72 hours) onset of unilateral peripheral facial palsy in isolation—that is, no features from the history, neurologic examination, or general examination suggest an alternative diagnosis. Red flags casting doubt on the diagnosis of Bell’s palsy include gradual onset, concurrent vertigo or hearing loss, vesicles in the external auditory canal, living in an area endemic for Lyme disease, risk factors for HIV, and systemic cancer, among others. When no red flags exist, and the diagnostic criteria for Bell’s palsy are used, additional testing is usually not necessary. Even without treatment, most patients, especially those with facial paresis rather than palsy, will have a complete recovery. A 10-day course of corticosteroids has been shown to significantly increase the likelihood of recovery; adding an antiviral does not significantly improve the likelihood of recovery, but the possibility that doing so may have a modest benefit, at most, cannot be ruled out. Residual effects of Bell’s palsy include permanent weakness and motor and nonmotor synkinesia, the latter including gustatory tearing and gustatory sweating (Frey syndrome).

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Supplemental Digital Content 5-1

Synkinesia after right facial nerve palsy. The 55-year-old woman in Case 5-5 developed a moderate right facial nerve palsy 20 years earlier as a consequence of the removal of a large acoustic neuroma, which gradually improved. When she blinks, co-contraction of the right orbicularis oris occurs, and when she smiles, co-contraction of the right orbicularis oculi occurs, causing the palpebral fissure to narrow; these are signs of aberrant regeneration of the facial nerve with synkinesia. © 2017 American Academy of Neurology.

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Case 5-5

A 55-year-old woman had undergone surgery for a large right acoustic neuroma 20 years earlier and was followed by her neurologist for headaches. Postoperatively, she had had moderate facial weakness that gradually improved, and she eventually developed an asymptomatic synkinesia. When she blinked, simultaneous movement of the right lips and mentalis occurred, and when she smiled, contraction of the orbicularis oculi occurred (Supplemental Digital Content 5-1,

Comment. This case demonstrates one of the complications of facial nerve palsy: the aberrant regeneration of motor fibers. The patient exhibits synkinesia between the orbicularis oculi and orbicularis oris, so that moving the mouth causes a contraction, which narrows the palpebral fissure, and eye closure causes retraction of the mouth. This symptom is often asymptomatic but, if bothersome, it can be treated with botulinum toxin.

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* Bell’s palsy is characterized by the spontaneous acute (72 hours or fewer) onset of a unilateral peripheral facial nerve palsy without any accompanying signs, with neither the history nor examination suggesting an alternative diagnosis.

* Sir Charles Bell determined that the seventh cranial nerve controlled the muscles of facial expression.

* A peripheral (lower motor neuron) facial palsy weakens all the ipsilateral facial muscles, including the frontalis and orbicularis oculi. A central (upper motor neuron) facial palsy weakens only the contralateral two-thirds of the face, sparing the frontalis.

* In addition to innervating the muscles of facial expression, the facial nerve also conveys sensation from the external auditory canal, pinna, mastoid, and mucosa of the palate; innervates the stapedius muscle and the lacrimal and minor salivary glands; and carries taste from the anterior two-thirds of the tongue.

* Factors suggesting a worse prognosis for recovery of Bell’s palsy include diabetes mellitus, hypertension, older age, complete paralysis, lack of improvement by 1 month, non-ear pain, and decreased tearing.

* The cause of Bell’s palsy is not known but may be due to reactivation of herpes simplex virus type 1.

* The return of the ability to whistle can be a useful way to document improvement in Bell’s palsy (assuming the patient could whistle before its onset).

* Although typically no objective sensory loss occurs with Bell’s palsy, pain around the ear and face may occur, which at times can be severe. Prolonged pain outside of these areas may be a sign that the patient has an alternative cause of facial palsy.

* Some have suggested that Bell’s palsy is actually a cranial polyneuropathy. But, anything more than subtle signs implicating other cranial nerves should be viewed as a potential red flag, casting doubt on the diagnosis of Bell’s palsy.

* About 7% of patients with Bell’s palsy will have a recurrence.

* For typical cases of Bell’s palsy, with no red flags from the history or examination, no further workup, including imaging, is necessary.

* If a patient with Bell’s palsy is imaged with MRI (typically not necessary), enhancement of the intracanalicular and labyrinthine segments of the facial nerve may be seen.

* Red flags casting doubt on the diagnosis of Bell’s palsy include gradual onset, involvement of other cranial nerves, concurrent vertigo or hearing loss, bilaterality, risk for Lyme disease or human immunodeficiency virus, and systemic cancer.

* Lyme disease is a common cause of peripheral facial palsy in endemic areas during the summer months, but in the absence of potential exposure and without other characteristic signs, routine testing is not recommended.

* A careful head and neck examination is important in patients with a peripheral facial palsy with particular attention for vesicles on the tympanic membrane, external auditory canal, or soft palate, indicating herpes zoster (Ramsay Hunt syndrome).

* A peripheral facial palsy is the most common neurologic manifestation of neurosarcoidosis and is particularly important to consider if bilateral.

* A peripheral facial palsy may the first sign of Guillain-Barré syndrome, progressing to limb weakness, but a variant of Guillain-Barré syndrome occurs with only bifacial palsy.

* To protect the cornea in patients with Bell’s palsy, lubricating drops should be used frequently during the day, and a lubricating gel should be used at night along with taping the lid closed or using a patch that does not rest on the cornea.

* The American Academy of Neurology evidence-based review gave a level A recommendation to the use of corticosteroids within the first 72 hours of onset to increase the likelihood of improvement for Bell’s palsy. Combining an antiviral with a corticosteroid does not significantly improve the outcome of Bell’s palsy, and their use was given a level C recommendation for a possible modest benefit, at best.

* Residual facial weakness after Bell’s palsy can cause a contracture, making it appear at rest that the normal side is weak with a flatter nasolabial fold and widened palpebral fissure. When facial function is tested, the weak side is readily apparent.

* A motor synkinesia is a complication of Bell’s palsy. This is usually asymptomatic but, if bothersome, can be treated with botulinum toxin.

* Two nonmotor synkinesias after Bell’s palsy include gustatory lacrimation (crocodile tears) and gustatory sweating, known as Frey syndrome.

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This article is dedicated to Donald H. Gilden, MD, FAAN (1937 to 2016), in recognition of his many contributions to Bell’s palsy and with appreciation of his friendship.

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