What are the clinical presentation and diagnosis of Bell's palsy?

Bell's Palsy: Clinical Presentation and Diagnosis

Bell's palsy is an acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours without an identifiable cause, characterized by rapid onset of unilateral facial weakness or paralysis involving the forehead. 1

Key Clinical Features

• Bell's palsy presents with rapid unilateral facial weakness or complete paralysis developing over less than 72 hours 2, 1
• Involvement of the forehead distinguishes it from central causes of facial weakness (such as stroke) 1, 3
• Associated symptoms may include:
  • Ipsilateral pain around the ear or face 1
  • Hyperacusis (increased sensitivity to sound) 1
  • Taste disturbance on the anterior two-thirds of the tongue 1
  • Dry eye and mouth due to autonomic fiber involvement 1

Diagnostic Approach

• Bell's palsy is a diagnosis of exclusion, requiring elimination of other causes of facial paresis/paralysis 2, 1
• The House-Brackmann facial nerve grading system is commonly used to assess severity, with grades ranging from 1 (normal) to 6 (total paralysis) 1
• Systematic assessment should include evaluation of all facial movements:
  • Raising eyebrows (frontalis muscle) 1
  • Closing eyes tightly (orbicularis oculi) 1
  • Smiling and puffing out cheeks 1

Red Flags Suggesting Alternative Diagnosis

• Bilateral facial weakness (rare in Bell's palsy) 1
• Slow progression beyond 72 hours 2, 1
• Involvement of other cranial nerves 1
• Isolated branch paralysis 1
• Second paralysis on the same side 1
• No recovery after 3 months 1
• History of head and neck cancer 2

Diagnostic Testing

• Routine laboratory testing and diagnostic imaging are NOT recommended for initial Bell's palsy diagnosis 1, 3
• MRI with and without contrast is the imaging test of choice when indicated for atypical presentations or no recovery after 3 months 1
• Electrodiagnostic testing may be offered to patients with complete facial paralysis but is NOT recommended for incomplete facial paralysis 1

Differential Diagnosis

• Other conditions that may cause facial paralysis include:
  • Stroke 2
  • Brain tumors 2
  • Tumors of the parotid gland or infratemporal fossa 2
  • Cancer involving the facial nerve 2
  • Systemic and infectious diseases (zoster, sarcoidosis, Lyme disease) 2, 3

Epidemiology and Risk Factors

• Bell's palsy affects all age groups but is more common in those 15 to 45 years old 2
• Higher risk in patients with:
  • Diabetes 2, 4
  • Upper respiratory ailments 2
  • Compromised immune systems 2
  • Pregnancy 2, 4
  • Hypertension 4
  • Obesity 4

Prognosis

• Approximately 70% of patients with complete paralysis recover facial function completely within 6 months 1
• Patients with incomplete paralysis have higher recovery rates, up to 94% 1
• Most patients begin showing signs of recovery within 2-3 weeks of symptom onset 1
• Complete recovery typically occurs within 3-4 months for most patients 1
• Children and pregnant women have better prognosis with recovery rates up to 90% 3

Complications

• Incomplete eyelid closure with resultant dry eye is a common short-term complication 5
• Approximately 30% of patients may experience permanent facial weakness with muscle contractures 1
• Synkinesis (involuntary co-contraction of certain facial muscles) may occur due to misdirected regrowth of facial nerve fibers 3
• Psychological impact due to facial appearance and difficulty expressing emotion 2

Eye Protection

• Eye protection is essential for patients with impaired eye closure to prevent corneal damage 1
• Protective measures include:
  • Lubricating ophthalmic drops used frequently throughout the day 1
  • Ophthalmic ointments for more effective moisture retention, particularly at night 1
  • Moisture chambers using polyethylene covers for nighttime protection 1
  • Eye patching or taping (with careful instruction on proper technique) 1
  • Sunglasses for outdoor protection 1

Follow-up Recommendations

• Patients should be reassessed or referred to a specialist if they have:
  • New or worsening neurologic findings at any point 1
  • Ocular symptoms developing at any point 1
  • Incomplete facial recovery 3 months after initial symptom onset 1