Facial Paralysis: Diagnosis and Treatment

Overview

Etiology & Differential Diagnosis

Bell Palsy (Idiopathic Facial Paralysis)

Definition & Minimum Diagnostic Criteria (Taverner)

1. Paralysis or paresis of all muscle groups on one side
2. Sudden onset
3. Absence of CNS disease signs
4. Absence of ear or cerebellopontine angle disease signs

Epidemiology

• Incidence: 23–37 per 100,000/year; up to 59/100,000 in those >65 years
• Equal sex distribution; slight female predominance under age 20
• ~70% present with complete paralysis; ~30% incomplete
• Bilateral in 0.3%; recurrence in ~9%; family history in 8%

Etiology

Clinical Features

• Onset: Acute — 50% reach maximum paralysis in 48 hours; nearly all within 3–4 days
• Pain: Retroauricular pain may precede paralysis by 1–2 days
• Taste impairment: Present in most patients (lesion proximal to chorda tympani junction); resolves within ~2 weeks
• Hyperacusis: Indicates stapedius muscle paralysis
• Lagophthalmos: Inability to close the eye — risk of corneal exposure injury
• Facial numbness/fullness reported in a small number of patients
• Bell's phenomenon: Upward rotation of the eyeball on attempted eyelid closure (lower motor neuron sign)

Grading: House-Brackmann Scale

Diagnostic Evaluation

Clinical Assessment

• Distinguish upper motor neuron (UMN) vs. lower motor neuron (LMN) lesion:
  • UMN: forehead sparing (bilateral cortical representation of frontalis)
  • LMN: entire ipsilateral face involved, including forehead

Electrodiagnostic Testing

• Electroneurography (ENoG): Compares compound action potential amplitude bilaterally. >90% degeneration indicates poor prognosis; used 4–14 days post-onset
• Electromyography (EMG): Denervation potentials appear 10+ days post-onset. Retention of voluntary motor units beyond day 7 is a favorable sign; fibrillation potentials at 10–14 days predict poor outcome with ~80% accuracy
• Nerve conduction velocity: 37–58 m/s = good outcome; <10 m/s = poor prognosis

Imaging

• MRI with gadolinium: Enhancement of the facial nerve is common even in healthy individuals, limiting specificity. More pronounced enhancement correlates with worse prognosis
• Indicated when: progressive course, associated masses, suspected neoplasm, or atypical features
• CT temporal bone: Trauma or cholesteatoma evaluation

Additional Testing (when indicated)

• Lyme serology (endemic areas or bilateral palsy)
• ACE level (sarcoidosis)
• HIV testing
• VZV serology

Prognosis

• 70% recover completely within 1–2 months; 85% achieve near-normal function
• Early return of some motor function in days 5–7 is the most favorable prognostic sign
• Return of taste in the first week is also a good sign
• When degeneration is complete, recovery proceeds by axonal regeneration — may take 2 years or longer and is often incomplete
• Incomplete paralysis at presentation → near-universal complete recovery

Treatment

1. Corticosteroids (First-Line)

• Typical regimen: Prednisolone 60 mg/day × 5 days, then taper over 5 days
• Improves the probability and speed of complete recovery

2. Antiviral Agents

• Evidence is conflicting — studies differ on benefit of adding antivirals to steroids
• Acyclovir or valacyclovir is often added given the HSV-1 etiology (low risk, potential benefit)
• In Ramsay Hunt syndrome: antiviral treatment (acyclovir/valacyclovir) combined with steroids is clearly beneficial; recovery rates are significantly better with combination therapy vs. steroids alone (~16–22% full recovery with RHS vs. ~70% with Bell palsy)

3. Eye Care

• Critical to prevent corneal exposure injury due to lagophthalmos
• Artificial tears (daytime), lubricating eye ointment (nighttime), eye patching
• Moisture chamber glasses if severe lagophthalmos

4. Surgical Decompression

• Reserved for cases with >90% ENoG degeneration and absent voluntary EMG potentials
• Controversial — the evidence base is limited
• Target: decompression at the meatal foramen (labyrinthine segment)

5. Botulinum Toxin

• For persistent synkinesis post-recovery
• Orbicularis oculi injection (~40 units) effectively reduces eyelid synkinesis; lower doses preferred to avoid ptosis — Cummings Otolaryngology

6. Physical Therapy / Facial Rehabilitation

• Includes neuromuscular reeducation, mime therapy, biofeedback
• Evidence: one meta-analysis found no benefit; another found Level C support for mime therapy
• Most useful for patients with incomplete recovery

7. Facial Reanimation Surgery (Permanent Palsy)

• Static procedures: Facial slings (xenograft/muscle transfers) — restore symmetry at rest
• Dynamic procedures: Nerve grafts (hypoglossal-facial nerve anastomosis, cross-facial nerve grafts), free muscle transfer

Ramsay Hunt Syndrome (Herpes Zoster Oticus)

• Etiology: VZV reactivation in geniculate ganglion
• Triad: Facial paralysis + otalgia + vesicular eruption on pinna/external auditory canal/palate/tongue
• ~10% of cases: rash appears after initial paralysis; ~25% rash precedes paralysis (better prognosis)
• Zoster sine herpete: VZV-mediated palsy without visible rash
• Prognosis worse than Bell palsy: full recovery in only 16–22% overall; 10% after complete palsy
• Treatment: Prednisone + valacyclovir (or acyclovir) — combination is superior to steroids alone

Special Situations