Description

• This paralysis may involve all of the modalities affected by the 7th cranial nerve:
  • Mimetic facial movement
  • Taste
  • Cutaneous sensation
  • Hearing acuity
  • Lacrimation
  • Salivation
• The most important feature in diagnosis and management of Bell palsy is the distinction between a peripheral and a central 7th nerve palsy.

Epidemiology

Pathophysiology

Nearly all cases of true Bell palsy are believed to arise from a viral infection of the facial nerve and, in particular, the geniculate ganglion.

Etiology

• Idiopathic: pregnancy-related
• Infectious
  • Herpes simplex virus 1
  • Human herpesvirus 6
  • Herpes zoster (without Ramsay Hunt syndrome)

Commonly Associated Conditions

• Associated illnesses can cause or predispose to an isolated facial nerve palsy but are important to distinguish from a classic Bell palsy.
• Rubella
• Lyme disease (Borrelia burgdorferi)
• Epstein-Barr virus (EBV)
• Cytomegalovirus (CMV)
• Mumps
• HIV
• Mycoplasma pneumoniae
• Sarcoidosis

History

• Mastoid or retroauricular pain ipsilateral to the side of developing symptoms (40–50% of patients)
• 50% of patients will have no clear sensory prodrome.
• Bell palsy often follows some identifiable infectious illness, such as viral upper respiratory tract infection (URI) symptoms, M. pneumoniae infection, Lyme disease, or infectious mononucleosis. However, an identified antecedent illness is not requisite for the diagnosis.
• The onset is almost always rapid, with progression to a fairly constant state of unilateral paresis or paralysis within hours to 2 to 3 days.
• As the weakness progresses, the patient (and family members) may note the following:
  • Difficulty with oral motor tasks (e.g., eating and drinking) due to inability to maintain mouth closure
  • Inability to completely close the eye on the affected side (sometimes leading untrained observers to note an eyelid “droop” on the normal side due to the contrast with normal eyelid closure and movements)
  • Decreased lacrimation and eye itching and burning
  • Hyperacusis
  • Ipsilateral facial numbness (less commonly)
  • Distortion of the taste of foods (dysgeusia)
• Bilateral symptoms (<1%) are distinctly rare and suggest an alternative diagnosis, such as Guillain-Barré syndrome or other infectious, inflammatory, or metabolic disease.

Physical Exam

• Weakness of all muscles of mimetic facial movement is noted on the affected side.
• A classic feature of peripheral facial nerve palsies is symmetric weakness or paralysis of the upper (frontalis), middle (orbicularis oculi), and lower (orbicularis oris) muscles on voluntary and involuntary mimetic movements. Having the patient wrinkle his or her forehead, raise his or her eyebrows, close his or her eyes tightly, and bare his or her teeth or smile, respectively, test these muscles.
• Occasionally, slow or absent spontaneous blinking on the affected side
• The corneal reflex should be decreased or absent on the affected side, but the consensual response on the unaffected side should be preserved.
• The sensory division of the 7th cranial nerve is tested by examining taste perception on the anterior tongue:
  • This is done by applying, ipsilaterally, swabs soaked in a sugar solution and a salt solution to the anterolateral aspect of the tongue, without allowing for mouth closure and dispersion of the substances to the other side. Taste sensation should be ipsilaterally decreased.
  • Despite complaints of retroauricular pain and unilateral facial “numbness,” abnormalities of cutaneous sensation typically are not verifiable by sensory testing in pure 7th nerve palsies. The presence of true diminution of sensation should raise the question of other cranial nerve involvement (e.g., 5th cranial nerve).
• Examination of the external auditory canal on both sides is crucial.
  • Vesicular lesions of the tympanic membrane indicate a zoster-associated palsy (i.e., Ramsay Hunt syndrome).
  • Purulent acute otitis media or evidence of trauma mandates aggressive antibiotic treatment and possibly urgent surgical subspecialty evaluation and imaging of the temporal bone.

Differential Diagnosis

• Trauma
  • Birth (especially forceps pressure to lateral face)
  • Congenital facial palsies should not be regarded as Bell palsy but rather symptomatic of some other cause.
  • Temporal bone/petrous bone fractures
  • Deep lacerations or trauma to parotid region
• Infection
  • Purulent acute otitis media/mastoiditis
  • Basilar meningitis
  • Petrous apicitis (Gradenigo syndrome)
  • Varicella-zoster virus (VZV; Ramsay Hunt syndrome)
  • Syphilis
  • Trichinosis
  • Tuberculosis
  • Leprosy
• Inflammatory
  • Sarcoidosis
  • Behçet disease
  • Giant cell arteritis
  • Polyarteritis nodosa
  • Guillain-Barré syndrome
  • Melkersson-Rosenthal syndrome: rare neurologic disorder characterized by recurring facial paralysis, swelling of the face and lips (usually the upper lip), and the development of folds and furrows in the tongue
• Tumors
  • Cerebellopontine angle tumors, osteosarcomas, cholesteatomas, neurofibromas, lymphoma
  • Hyperostosis cranialis interna, osteopetrosis
• Metabolic
  • Diabetes (nerve ischemia)
  • Hyperparathyroidism
  • Hypothyroidism
  • Porphyria
• Congenital/genetic
  • Congenital absence or hypoplasia of depressor anguli oris muscle
  • Möbius syndrome
  • Chiari malformation
  • Syringobulbia

Diagnostic Tests and Interpretation

General Measures

• Eye protection and lubrication: A significant risk for corneal injury is best managed by applying artificial tear solutions at least 3 to 4 times daily and lubricating gels (e.g., Lacri-Lube) at night. Patching and protective eyewear, during active play and sleep, are usually prescribed based on the degree of remaining eyelid closure.
• Corticosteroids: prednisone, considered only within the first 72 hours of symptoms. Recommended dose: 1 mg/kg/24 h PO (maximum 80 mg) once daily for 5 days, with a taper over the following 5 days. Recent evidence suggests that corticosteroids may worsen long-term outcomes in cases of facial palsy associated with Lyme disease. Therefore, careful consideration of this etiology prior to prescribing steroids, and prompt follow-up of laboratory results/Lyme serologies, ought to be priority. Consider adjustment of treatment strategy if Lyme serologies are positive for acute infection.
• Famciclovir: most clearly indicated for the treatment of Ramsay Hunt syndrome. It is also used empirically by some practitioners in standard Bell palsy management, although evidence for its supplementary use to corticosteroids is still relatively weak; see discussion in the following text. Recommended dose for children ≥45 kg and adolescents: 250 mg t.i.d. PO for 5 to 7 days. Valacyclovir 20 mg/kg/dose (max dose: 1,000 mg/dose) t.i.d. PO for 7 days may be used as an alternative agent for children <45 kg. Generally, any evidence of vesicular eruption in the ear canal or face should be treated promptly with antiherpetic agents (famciclovir or valacyclovir preferred over acyclovir), as outcomes from VZV-associated palsies are reported to be worse in general.

Medication (Drugs)

• Corticosteroids: Recent large series and meta-analyses indicate that treatment with corticosteroids is effective in reducing the risk of incomplete recovery; however, this treatment seems to be only effective if initiated within the first 48 hours of symptoms. The occurrence of synkinesias is less likely in patients treated with steroids within 48 hours across all age groups.
• Antivirals: There is little or no benefit to therapy with antivirals alone. Recent meta-analyses suggest that antivirals may provide benefit when used in combination with corticosteroids, both in functional recovery and reduction of long-term sequelae. However, the quality of evidence remains low to moderate. Famciclovir, when used in combination with corticosteroids, provides superior benefit compared to acyclovir, and so famciclovir seems to be the antiviral drug of choice for idiopathic facial palsy. The best evidence for added efficacy of antivirals in combination with corticosteroids still seems to be in cases with particularly severe degrees of paralysis or in cases with suspected herpes zoster infection.
• Antibiotics: In areas where Lyme disease is endemic, many practitioners will begin treatment with oral antibiotics presumptively, while awaiting serologies (recall that the IgM titer is the most useful in the acute setting). (See “Lyme Disease” chapter.)

Diagnostic Procedures/Other

Surgical decompression: Previously, surgical decompression of the 7th nerve had been proposed as a possible treatment in cases where recovery was delayed or the clinical course more severe. No clinical evidence to support the benefit of this strategy has emerged. Surgical decompression is best reserved for “other” cases of facial nerve palsy in which there is a definable syndrome of nerve compression due to extrinsic factors, such as exostoses, tumor, etc.

Issue for Referral

Subspecialty consultation: In general, patients are referred if their recovery time is prolonged or if there is a relapsing pattern or other deviations from the expected course. However, the presence of other questionable cranial nerve involvement, recent trauma, meningeal symptoms, or neurologic findings (e.g., eye movement abnormalities, acute hemiparesis, etc.) should be viewed with great concern and evaluated in an urgent care setting.

Additional Therapies

The decision to pursue physical therapy after Bell palsy is a matter of personal preference for the practitioner and family.

• A recent study of a large number of patients, comparing oral corticosteroids versus corticosteroids plus Kabat physical rehabilitation, showed a significant degree of improvement in the latter group in functional facial movement outcomes, at a much faster rate. There was no statistically significant difference in the incidence of synkinesias (abnormal involuntary movements that accompany a normally executed voluntary movement).
• However, the application of physical therapy in Bell palsy recovery remains controversial, and the latest clinical practice guidelines from the American Academy of Otolaryngology—Head and Neck Surgery include no recommendation for facial physical therapy. There is no evidence that facial physiotherapy is harmful.

Diet

There are no dietary restrictions that affect the outcome of Bell palsy.

Patient Teaching

Minimizing risk for injury to the cornea ipsilateral to the facial palsy may require either restricting some activities where debris or contusions to the eye are likely or wearing protective eyewear during such activities (e.g., beach activities and competitive sports). These restrictions only need to be in effect so long as there is inadequate closure of the eyelid on the affected side.

Prognosis

• 60–70% full-recovery rate from isolated 7th nerve palsy
• Signs of recovering function (generally improving control of mimetic movement) are typically apparent by the 3rd week after onset.
• Prognosis for recovery seems to be worse with either a secondary deterioration in function after 2 to 4 days, no signs of recovery after 3 weeks, or demonstrated gadolinium enhancement of the affected facial nerve on MRI.
• Of patients with less than total recovery, many will experience at least partial return to normal function; cosmetic results vary in this group.
• Outcome of idiopathic facial palsy as a pregnancy complication seems to be less favorable (~55% full recovery).
• Up to 7% of patients may experience a second occurrence at some point in the future.

Complications

• Corneal injury, due to decreased lacrimation and poor eye closure
• Several sequelae, generally related to aberrant reinnervation of affected end organs, are observed after an episode of Bell palsy.
  • Various synkinesias including the Marin-Amat phenomenon (spontaneous eye closure with mouth opening or its converse)
  • Blepharospasm, hemifacial spasm, facial contractures
  • The “crocodile tears” phenomenon (eating provokes ipsilateral tearing) results from crossed reinnervation between lacrimal and salivary parasympathetic fibers.

ICD-9

• 351.0 Bell’s palsy
• 351.0 Bell’s palsy

ICD-10

G51.0 Bell’s palsy

SNOMED

193093009 Bell’s palsy (disorder)