What is facial nerve palsy?

Facial Nerve Palsy

Facial nerve palsy is a rapid unilateral facial nerve paresis (weakness) or paralysis (complete loss of movement) that leads to the partial or complete inability to voluntarily move facial muscles on the affected side of the face. 1

Definition and Clinical Presentation

• Facial paralysis refers to complete inability to move the face, while facial paresis indicates incomplete ability to move the face 1
• Bell's palsy, the most common form of facial nerve palsy, is defined as acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours and without an identifiable cause 1, 2
• Symptoms typically develop rapidly (within 72 hours) and may include:
  • Inability to close the eyelid on the affected side 1
  • Oral incompetence (difficulty controlling mouth movements) 1
  • Dryness of the eye or mouth 1
  • Taste disturbance or loss 1
  • Hyperacusis (increased sensitivity to sound) 1
  • Sagging of the eyelid or corner of the mouth 1
  • Ipsilateral pain around the ear or face 1

Etiology

• While the exact mechanism of Bell's palsy is currently unknown, a viral etiology is suspected 1
• Facial paresis or paralysis is thought to result from facial nerve inflammation and edema 1
• As the facial nerve travels through a narrow canal in the temporal bone, swelling may lead to nerve compression resulting in temporary or permanent nerve damage 1
• Herpes simplex virus type 1 is a possible causative agent 3

Epidemiology

• Bell's palsy can affect men, women, and children but is more common in those 15 to 45 years old 1
• Higher incidence in patients with:
  • Diabetes 1, 3
  • Upper respiratory ailments 1
  • Compromised immune systems 1
  • During pregnancy 1

Differential Diagnosis

Other conditions that may cause facial paralysis include:

• Stroke 1
• Brain tumors 1
• Tumors of the parotid gland or infratemporal fossa 1
• Cancer involving the facial nerve 1
• Systemic and infectious diseases:
  • Herpes zoster (Ramsay Hunt syndrome) 1
  • Sarcoidosis 1
  • Lyme disease 1

Diagnostic Approach

• Bell's palsy is a diagnosis of exclusion requiring careful elimination of other causes 1, 2
• Red flags requiring further investigation include:
  • Advanced age (increased stroke risk) 2
  • Bilateral facial weakness (rare in Bell's palsy) 2
  • New or worsening neurologic findings 2
  • Slow progression of symptoms (>72 hours) 2
• Diagnostic testing:
  • Routine laboratory testing is NOT recommended for typical presentations 2
  • Diagnostic imaging is NOT routinely recommended for typical cases 2
  • MRI may be considered to rule out stroke and other causes in atypical presentations 2
  • Electrodiagnostic testing may be offered only to patients with complete facial paralysis 2

Treatment

• Oral steroids within 72 hours of symptom onset are recommended 2, 3
• Antiviral therapy alone is NOT recommended, but may be offered in combination with oral steroids 2, 4
• Eye protection is essential for patients with impaired eye closure to prevent corneal damage 2
• Physical therapy modalities including electrostimulation, exercise, and massage have not been shown to be beneficial or harmful 5

Prognosis

• Bell's palsy is typically self-limited 1
• Most patients begin showing recovery within 2-3 weeks after onset of symptoms 4
• Complete recovery typically occurs within 3-4 months 4
• Without treatment, facial function is completely restored in:
  • Approximately 70% of patients with complete paralysis within 6 months 4
  • Up to 94% of patients with incomplete paralysis 4
• Potential complications include:
  • Short-term: Incomplete eyelid closure with resultant dry eye 3
  • Long-term: Permanent facial weakness with muscle contractures 3

When to Refer

• Refer to a facial nerve specialist if new or worsening neurologic findings develop 2
• Consider referral for patients without improvement after the expected recovery period 6