Facial nerve palsy

• Idiopathic (most common cause of peripheral facial nerve palsy): Acute idiopathic peripheral facial palsy is also known as Bell palsy. ^[1]
• Secondary
  • Trauma (e.g., temporal bone fracture)
  • Infection
    • Herpes zoster (Ramsay Hunt syndrome)
    • Borreliosis (Lyme disease)
    • HSV reactivation
    • HIV
    • Malignant otitis externa
  • Tumors (parotid gland tumors, acoustic neuroma)
  • Pregnancy
  • Diabetes mellitus
  • Guillain-Barré syndrome
  • Sarcoidosis (Heerfordt syndrome)
  • Amyloidosis
  • Stroke

References:^[2][3][4][5]

• The muscles responsible for eyelid and forehead movements are innervated by fibers from both sides.
  • Central facial palsy: There is a unilateral upper motor neuron lesion between the cortex and nuclei in the pons (corticobulbar tract), but the muscles of the eyelids and forehead are still supplied by input from the other side, so function is preserved (forehead sparing).
  • Peripheral facial palsy: There is a unilateral lower motor neuron lesion between the nuclei and muscles, which results in the paralysis of the ipsilateral eyelid and forehead muscles because no other input reaches these muscles.
• The lower facial muscles are only innervated by fibers from the contralateral hemisphere (via ipsilateral nuclei and the ipsilateral peripheral nerve), so they are paralyzed in both central and peripheral facial palsy.

References:^[6]

Central vs. peripheral facial nerve palsy ^[6]

Additional signs of peripheral facial palsy

• Sensory disturbances
  • Painful sensation around or behind the ear ^[6]
  • Impairment of taste in the anterior tongue
  • Hyperacusis
• Dry mouth (as a result of decreased saliva production)
• Ocular features
  • Bell's phenomenon: a physiologic, reflexive movement of the eye (upward and outward) that occurs when the eyelid is actively closed
  • Lagophthalmos: The patient cannot fully close the eyes (due to paralysis of the orbicular oculi muscle). ^[7]
  • Decreased lacrimation
  • Corneal ulceration and keratitis
  • Ectropion
• Facial synkinesis; : involuntary movements of the facial muscles; (e.g., facial spasms while closing the eyes)

In central facial palsy, paralysis is contralateral to the lesion, and eyelid and forehead muscles are not affected!

Clinical evaluation ^[8][9][10]

Bell palsy is a clinical diagnosis of exclusion.

• Medical history
  • Ask about symptom onset and duration (e.g., acute vs. progressive).
  • Assess for possible secondary causes, e.g., stroke, tumors, recent infections, and; exposure from outdoor trips.
• Physical examination
  • Evaluate for facial asymmetry at rest.
  • Ask the patient to perform facial movements.
    • Assess for asymmetries and facial muscle strength.
    • Differentiate between motor signs in central and peripheral facial palsy.
  • Perform a complete neurological examination: Look for focal neurological signs.
  • Evaluate for signs indicative of a secondary cause, e.g., shingles , herpes zoster oticus , erythema migrans , tick bites, signs of trauma.

Typical features of Bell palsy include acute (< 72 hours), nonprogressive, unilateral peripheral facial nerve paralysis, with no identified cause after thorough clinical evaluation. ^[9]

When an acute central cause is suspected (e.g., other acute focal neurological symptoms are present), evaluate for ischemic stroke. Consider a tumor in patients with gradual onset, or slowly progressing neurological symptoms (e.g., change in mental status, involvement of select branches of the facial nerve and/or other cranial nerves, or other subacute focal neurological deficits). ^[4][9]

Severity assessment ^[9][11]

• Determine the level of dysfunction of forehead movements, eye closure, and mouth closure.
• Consider the use of a validated severity scale.

Diagnostic studies ^[8][9][10]

Diagnostic studies are not routinely needed for acute unilateral facial nerve palsy unless a secondary cause is suspected (see “Etiology”) based on atypical symptoms and/or abnormal physical examination findings (See “Clinical features” and “Clinical evaluation”). Specialist consultation is advised.

• Laboratory studies: Consider for select infectious causes.
  • VZV: e.g., PCR or serological studies (See “Diagnostics for shingles.”)
  • Lyme disease: e.g., ELISA IgM and IgG antibodies for Borrelia, Western blot (See “Diagnostics for Lyme disease.”)
• Neuroimaging should be performed if neoplastic, vascular, or traumatic causes are suspected, for example:
  • Suspected peripheral nerve tumors: e.g., cholesteatoma, facial schwannoma, parotid gland tumor, infratemporal fossa tumors ^[9]
  • Suspected primary brain tumor or metastasis
  • Acute stroke (See “Diagnosis of stroke.”)
  • Traumatic brain injury, e.g., basilar skull fracture (See also “Diagnostics for TBI.”)
• Other neurological studies
  • Consider nerve conduction studies: e.g., for patients with Bell palsy PLUS complete facial nerve paralysis, or suspected polyneuropathy (e.g., multiple sclerosis, Guillain Barré syndrome)
  • Consider audiology to evaluate for sensorineural hearing loss (SNHL): e.g., in patients with VZV, TBI, and suspected peripheral nerve or brain tumors

Up to 25% of acute facial nerve palsy cases may be attributed to Lyme disease in highly endemic areas. ^[9]

Recommendations in this section are consistent with the 2013 American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) Bell palsy guidelines and the 2012 American Academy of Neurology (AAN) guideline update on steroids for Bell palsy (reaffirmed in January 2020). ^[8][9]

Begin initial management of ischemic stroke without delay if acute central facial nerve palsy is suspected.

Symptomatic therapy ^[8][9][10]

Provide symptom-based treatment for all patients (regardless of the cause).

• Incomplete eye closure: : Initiate eye care; (e.g., artificial tears; , eye ointment, and/or taping or patching of the eye). ^[9]
• Incomplete mouth closure: Advise the patient on proper lip and mouth care.
• Persistent facial nerve paresis (≥ 3 months): Consider physical therapy and facial reconstructive options. ^[9][10]

Consider early ophthalmology referral for patients with severe facial nerve palsy, severe, persistent lagophthalmos, or other ocular symptoms (e.g., pain, itching, irritation). ^[9]

Targeted treatment

Bell palsy ^[8][9][10]

Idiopathic peripheral facial nerve palsy is self-limited, but early treatment is recommended to improve recovery time and prevent incomplete recovery. ^[9]

• Oral glucocorticoids: Consider for all patients (regardless of severity). ; ^[9]
  • Start early (i.e., within 48–72 hours of symptom onset)
  • Available agents: prednisone OR prednisolone ^[9]
• Antivirals
  • Consider adding an antiviral to steroid therapy (do not use as monotherapy). ^[8][9]
  • Available agents: acyclovir; OR valacyclovir
• Surgical decompression ^[9][10]
  • Not routinely recommended because of severe risks and unclear benefits
  • Consider urgent surgical (e.g., plastic surgery, ENT) referral for patients with severe facial nerve involvement (confirmed on nerve conduction studies). ^[9]
• Follow up with specialist consult and/or advanced studies if the patient has any of the following: ^[9][12]
  • No signs of improvement in 2–3 weeks ^[10]
  • Persistent (≥ 3 months), progressive, and/or recurrent symptoms

Initiate therapy (i.e., oral glucocorticoids with or without antivirals) within 48–72 hours of symptom onset. ^[8][9][10]

Secondary facial nerve palsy

Consider the following depending on the suspected etiology.

• Peripheral causes
  • Antiviral therapy for herpes zoster (see “Treatment” in “Shingles”) ^[13]
  • Antibiotic therapy for Lyme disease or otitis media (see “Treatment” in “Lyme disease” and “Otitis media”) ^[14]
  • Immunosuppressants for autoimmune diseases or autoinflammatory diseases (see “Treatment” sections in “Guillain-Barré syndrome” and “Sarcoidosis”)
• Central causes: Consult the appropriate specialist to determine the best treatment options (See “Treatment” sections in “Ischemic stroke,” “Intracerebral hemorrhage,” “Multiple sclerosis,” and “Brain tumors.”)
• Traumatic facial nerve palsy: a common complication of basilar skull fractures (e.g., temporal bone fractures) ^[15]
  • Obtain urgent surgical consult (e.g., neurosurgery, ENT).
  • Delayed or incomplete paralysis: conservative management with high-dose corticosteroid therapy
  • Immediate and complete paralysis: surgical exploration and decompression

• Idiopathic facial palsy: complete recovery in ∼ 85% of cases (within 3 weeks)
• Misdirected regrowth of nerve fibers can lead to persistent disorders (e.g., synkinesias)

References:^[16][17]