Bell's Palsy (Adult)

1. Topic Overview

Clinical Summary

Bell's palsy is the most common cause of acute unilateral peripheral facial paralysis, accounting for approximately 60-75% of all cases of acute facial palsy. [1,2] It is characterised by sudden-onset lower motor neuron (LMN) weakness affecting all muscle groups on one side of the face, including the forehead musculature. The condition represents a diagnosis of exclusion, made after ruling out identifiable secondary causes such as Ramsay Hunt syndrome, Lyme disease, stroke, and neoplastic lesions. [3]

The underlying aetiology remains incompletely understood, but substantial evidence implicates herpes simplex virus type 1 (HSV-1) reactivation within the geniculate ganglion, leading to inflammation, oedema, and subsequent compression of the facial nerve within the narrow confines of the fallopian canal in the temporal bone. [4,5] This inflammatory process results in demyelination and, in severe cases, axonal degeneration with Wallerian degeneration.

Prognosis is generally favourable, with approximately 70% of patients achieving complete recovery without treatment. Early initiation of corticosteroid therapy within 72 hours of symptom onset significantly improves outcomes, increasing complete recovery rates to 85-95%. [6,7] The role of antiviral agents remains controversial; current high-quality evidence does not support their routine use in Bell's palsy, though they are indicated in Ramsay Hunt syndrome. [8]

Key Facts

Clinical Pearl: The Forehead Test

"Can You Wrinkle Your Forehead?": This single clinical observation distinguishes Bell's palsy from stroke in the majority of cases. In Bell's palsy (LMN lesion), the forehead IS affected - the patient cannot wrinkle the forehead or raise the eyebrow on the affected side. In stroke (UMN lesion), the forehead is SPARED due to bilateral cortical representation of the upper face. This is the critical bedside distinction that guides further investigation.

Clinical Pearl: Vesicles = Not Bell's Palsy

Check the Ear: If vesicles are present in the external auditory canal, on the pinna, or on the soft palate, the diagnosis is Ramsay Hunt syndrome (herpes zoster oticus) caused by VZV reactivation, NOT Bell's palsy. This distinction is crucial as Ramsay Hunt syndrome requires antiviral therapy (aciclovir or valaciclovir) in addition to corticosteroids and carries a worse prognosis. [10]

Clinical Pearl: Eye Care is Non-Negotiable

Prevent Corneal Catastrophe: The inability to fully close the eyelid (lagophthalmos) leads to corneal exposure, desiccation, and risk of exposure keratopathy and corneal ulceration. Aggressive eye protection with artificial tears, lubricating ointment, and nocturnal taping is essential and should be initiated immediately. A corneal ulcer is a preventable iatrogenic complication. [11]

Why This Matters Clinically

Bell's palsy presents commonly in primary care and emergency departments, often causing significant patient anxiety due to fears of stroke. Rapid, accurate clinical assessment can distinguish Bell's palsy from stroke and other serious pathology. Early corticosteroid treatment substantially improves outcomes but must be initiated within 72 hours. Proper eye care prevents sight-threatening complications. While prognosis is generally excellent, incomplete recovery causes substantial psychological distress, social anxiety, and functional impairment affecting communication and facial expression.

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2. Epidemiology

Incidence and Prevalence

Bell's palsy is the most common acute mononeuropathy and the most frequent cause of unilateral facial paralysis worldwide. [1,2]

Demographics

Risk Factors

Established Risk Factors (Evidence-Based):

Associated Conditions:

• Immunocompromised states (HIV, organ transplant recipients)
• Pre-eclampsia and eclampsia (in pregnancy-associated cases)
• Hypothyroidism
• Multiple sclerosis (demyelinating lesions affecting CN VII)

NOT Risk Factors (Common Misconceptions):

• Cold exposure or draughts (no evidence)
• Stress alone (no direct evidence)
• Dental procedures (unless direct nerve trauma)

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3. Pathophysiology

Aetiology: The Viral Hypothesis

The predominant theory for Bell's palsy pathogenesis involves reactivation of latent herpes simplex virus type 1 (HSV-1) from the geniculate ganglion. [4,5] This hypothesis is supported by:

1. PCR evidence: HSV-1 DNA detected in endoneurial fluid of Bell's palsy patients during surgical decompression [4]
2. Serological studies: Elevated HSV-1 antibody titres in affected patients
3. Anatomical studies: HSV-1 latency demonstrated in human geniculate ganglia
4. Clinical parallels: Similar pathophysiology to herpes labialis reactivation

However, it is important to note that viral DNA detection does not prove causation, and the viral hypothesis remains unproven. Alternative or contributing factors may include:

• Autoimmune mechanisms (molecular mimicry)
• Ischaemic injury to the facial nerve
• Hereditary predisposition (anatomically narrow fallopian canal)

Anatomical Basis: The Facial Nerve Course

Understanding the facial nerve anatomy is essential for comprehending the clinical features and prognostic implications of Bell's palsy.

Facial Nerve Segments:

Key Anatomical Point: The labyrinthine segment is the narrowest portion of the fallopian canal (bony facial canal), making it the most vulnerable to compression from inflammatory oedema. This explains why Bell's palsy causes complete hemifacial weakness regardless of the site of inflammation within the canal.

Pathophysiological Sequence

BELL'S PALSY: PATHOPHYSIOLOGICAL CASCADE

Step 1: VIRAL REACTIVATION
    HSV-1 reactivation in geniculate ganglion
    (Trigger: immunosuppression, stress, infection)
                    ↓
Step 2: INFLAMMATION
    Inflammatory response with lymphocytic infiltration
    Cytokine release (TNF-α, IL-1β, IL-6)
    Oedema of nerve and surrounding tissues
                    ↓
Step 3: COMPRESSION
    Swollen nerve compressed within rigid fallopian canal
    Especially at labyrinthine segment (narrowest point)
    Venous congestion → further oedema (vicious cycle)
                    ↓
Step 4: NERVE INJURY
    Mild cases: Neuropraxia (conduction block, myelin preserved)
    Moderate: Axonotmesis (axon damage, myelin disruption)
    Severe: Neurotmesis (complete nerve disruption)
                    ↓
Step 5: CLINICAL MANIFESTATION
    Acute facial weakness (hours to 48 hours)
    Additional features: altered taste, hyperacusis, decreased lacrimation
                    ↓
Step 6: RECOVERY (Variable)
    Neuropraxia: Complete recovery in 3-8 weeks
    Axonotmesis: Recovery over months; may have synkinesis
    Neurotmesis: Poor recovery; aberrant regeneration

Nerve Injury Classification (Sunderland/Seddon)

Facial Nerve Functions: Clinical Correlates

The facial nerve carries multiple functional components, explaining the varied symptoms in Bell's palsy:

Motor Branch Distribution (Mnemonic: "Two Zebras Bit My Cat")

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4. Clinical Presentation

Typical Presentation

The classic presentation of Bell's palsy is acute-onset unilateral facial weakness developing over hours to 1-2 days, reaching maximum severity within 72 hours. [1,2]

Cardinal Symptoms:

Symptom Onset Characteristics:

• Onset typically overnight or upon waking
• Maximal weakness reached within 72 hours (usually 24-48 hours)
• Progression beyond 3 weeks suggests alternative diagnosis
• May be preceded by viral prodrome (URTI symptoms)

Clinical Signs

Inspection at Rest:

• Facial asymmetry (affected side droops)
• Widened palpebral fissure (lagophthalmos)
• Flattened nasolabial fold
• Drooping mouth corner
• Smoothed forehead furrows

Facial Motor Examination:

Bell's Phenomenon:

When attempting to close the eyes, the eyeball on the affected side rotates upward and outward (normal protective reflex), but because the eyelid cannot close, this movement becomes visible. A positive Bell's phenomenon indicates intact superior rectus function and provides some corneal protection.

Otoscopic Examination: Critical Step

ALWAYS examine the external auditory canal and pinna:

Red Flag Features

[!CAUTION] Red Flags Requiring Further Investigation:

Forehead SPARED (UMN Pattern):

• Suggests central lesion (stroke, tumour)
• Urgent stroke pathway if acute onset with other neurological signs

Vesicles Present:

• Ramsay Hunt syndrome (VZV)
• Add aciclovir 800mg 5x daily for 7 days
• Worse prognosis than Bell's (complete recovery 50-70%)

Bilateral Facial Weakness:

• Guillain-Barre syndrome (ascending weakness, areflexia)
• Lyme disease (especially if endemic area, tick exposure)
• Sarcoidosis (Heerfordt syndrome: uveitis, parotid enlargement, fever)
• Bilateral Bell's (rare; diagnosis of exclusion)

Progressive Weakness Over Weeks:

• Tumour (acoustic neuroma, facial nerve schwannoma, parotid malignancy)
• Cholesteatoma (associated hearing loss, otorrhoea)
• Requires MRI internal auditory meati and parotid

No Recovery by 3-4 Months:

• Consider misdiagnosis
• MRI to exclude tumour
• Refer to neurology/ENT

Recurrent Episodes:

• Melkersson-Rosenthal syndrome (facial palsy, fissured tongue, lip swelling)
• Tumour
• Investigate with MRI

Other Cranial Nerve Involvement:

• Brainstem lesion (stroke, demyelination, tumour)
• Skull base pathology (nasopharyngeal carcinoma, meningitis)
• Requires urgent imaging

Limb Weakness, Sensory Symptoms, Ataxia:

• Guillain-Barre syndrome
• Multiple sclerosis
• Brainstem stroke
• Urgent neurological assessment

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5. Clinical Examination

Structured Examination Approach

Introduction and Consent:

• Introduce yourself, confirm patient identity
• Explain examination
• Position patient sitting upright, good lighting, face fully visible

Observation (Before Touching):

• Facial asymmetry at rest
• Blink rate and symmetry
• Spontaneous facial movements
• Palpebral fissure size comparison
• Nasolabial fold depth
• Presence of any skin lesions, vesicles, or swelling

Systematic Facial Nerve Motor Examination:

Essential Additional Examinations:

House-Brackmann Facial Nerve Grading System

The House-Brackmann (HB) scale is the most widely used system for grading facial nerve function. [16] It provides a standardised method for documenting severity and tracking recovery.

Clinical Application of House-Brackmann:

• Document at presentation (baseline)
• Repeat at follow-up (track recovery)
• HB I-II at presentation = excellent prognosis
• HB V-VI at presentation = higher risk of incomplete recovery
• Useful for communication between clinicians
• Required for clinical trials and outcome studies

Sunnybrook Facial Grading System

For more detailed assessment, particularly in research and rehabilitation settings, the Sunnybrook system provides a composite score (0-100) evaluating:

• Resting symmetry
• Symmetry of voluntary movement
• Synkinesis

Special Clinical Tests

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6. Differential Diagnosis

Critical Differential: UMN vs LMN Facial Weakness

Anatomical Explanation: The upper facial muscles (frontalis, orbicularis oculi) receive bilateral cortical innervation - both the ipsilateral and contralateral motor cortex send fibres to the facial nucleus for these muscles. Therefore, a unilateral UMN lesion (stroke) leaves upper facial function relatively preserved because the intact contralateral cortex continues to supply these muscles. In contrast, an LMN lesion (Bell's palsy) affects the final common pathway, eliminating all motor supply to the ipsilateral facial muscles.

Comprehensive Differential Diagnosis

Infectious Causes:

Neoplastic Causes:

Inflammatory/Autoimmune Causes:

Vascular Causes:

Traumatic Causes:

Other Causes:

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7. Investigations

Bedside Investigations (First-Line)

Bell's palsy is a clinical diagnosis. In typical presentations, no investigations are required. [3]

Laboratory Tests (Selective)

Electrodiagnostic Studies

Clinical Utility of Electrodiagnostic Testing:

• Not routinely required for typical Bell's palsy
• Consider if complete paralysis (HB VI) at presentation
• Helpful for prognostication in severe cases
• ENoG most useful between days 3-14
• EMG useful after 2-3 weeks to assess denervation and early reinnervation

Imaging

Key Point: Routine imaging is NOT indicated in typical Bell's palsy. Reserve imaging for atypical features, no recovery, or progressive course.

Diagnostic Criteria Summary

Bell's palsy is a diagnosis of exclusion requiring:

1. Acute onset (maximum weakness within 72 hours)
2. Unilateral LMN facial weakness (forehead involved)
3. No identifiable cause on history and examination
4. Absence of red flag features

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8. Management

Management Algorithm

BELL'S PALSY: MANAGEMENT ALGORITHM

PRESENTATION: Acute unilateral facial weakness
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 1: CONFIRM DIAGNOSIS                                                     │
│                                                                              │
│ • LMN pattern (forehead affected)?    YES → Likely Bell's palsy             │
│ • Forehead spared?                    YES → Consider stroke (UMN) → Stroke  │
│                                             pathway                          │
│ • Vesicles visible?                   YES → Ramsay Hunt → Add antivirals    │
│ • Bilateral weakness?                 YES → GBS/Lyme/Sarcoid → Investigate  │
│ • Progressive over weeks?             YES → Tumour → MRI urgently           │
│ • Other cranial nerve involvement?    YES → Brainstem lesion → Imaging      │
└──────────────────────────────────────────────────────────────────────────────┘
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 2: CORTICOSTEROIDS (START WITHIN 72 HOURS)                              │
│                                                                              │
│ FIRST-LINE REGIMEN:                                                          │
│ • Prednisolone 50mg once daily for 10 days                                  │
│   OR                                                                         │
│ • Prednisolone 60mg once daily for 5 days, then taper over 5 days           │
│                                                                              │
│ EVIDENCE: NNT = 9 for complete recovery [6,7]                               │
│ • Complete recovery: 94% (steroids) vs 81.6% (placebo) at 9 months          │
│ • Benefit greatest if started within 72 hours of onset                       │
│                                                                              │
│ CONTRAINDICATIONS (relative):                                                │
│ • Active peptic ulcer disease                                                │
│ • Uncontrolled diabetes (still treat; monitor glucose)                       │
│ • Active tuberculosis or systemic infection                                  │
│ • Psychosis                                                                  │
│                                                                              │
│ PREGNANCY: Prednisolone is safe; benefits outweigh risks                     │
└──────────────────────────────────────────────────────────────────────────────┘
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 3: ANTIVIRALS - NOT ROUTINELY RECOMMENDED FOR BELL'S PALSY             │
│                                                                              │
│ COCHRANE REVIEW (2019): No significant benefit of antivirals alone or       │
│ combined with steroids compared to steroids alone [8]                        │
│                                                                              │
│ CURRENT EVIDENCE:                                                            │
│ • Antivirals alone: No benefit                                              │
│ • Antivirals + steroids: No additional benefit over steroids alone          │
│                                                                              │
│ ⚠ EXCEPTION: RAMSAY HUNT SYNDROME (vesicles present)                        │
│ • Aciclovir 800mg 5 times daily for 7 days                                  │
│   OR                                                                         │
│ • Valaciclovir 1000mg 3 times daily for 7 days                              │
│ • PLUS prednisolone (as above)                                              │
│                                                                              │
│ SEVERE BELL'S PALSY (HB V-VI)?                                              │
│ • Some guidelines suggest considering antivirals + steroids                  │
│ • Evidence weak; discuss risks/benefits with patient                         │
└──────────────────────────────────────────────────────────────────────────────┘
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 4: EYE CARE (ESSENTIAL - DO NOT OMIT)                                  │
│                                                                              │
│ GOAL: Prevent exposure keratopathy and corneal ulceration                   │
│                                                                              │
│ DAY:                                                                         │
│ • Artificial tears (carmellose 0.5% or hypromellose 0.3%)                   │
│ • Apply every 1-2 hours while awake                                         │
│ • Preservative-free preferred if using frequently                            │
│                                                                              │
│ NIGHT:                                                                       │
│ • Lubricating eye ointment (Lacri-Lube or similar)                          │
│ • Tape eyelid closed with micropore tape if incomplete closure              │
│ • Consider moisture chamber/swimming goggles                                 │
│                                                                              │
│ ADDITIONAL MEASURES:                                                         │
│ • Protective glasses when outdoors (wind, dust)                              │
│ • Avoid air conditioning directly on face                                    │
│                                                                              │
│ ⚠ RED FLAG - REFER OPHTHALMOLOGY URGENTLY IF:                               │
│ • Red eye                                                                    │
│ • Eye pain                                                                   │
│ • Photophobia                                                                │
│ • Visual disturbance                                                         │
│ • Suspected corneal ulcer                                                    │
└──────────────────────────────────────────────────────────────────────────────┘
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 5: PATIENT EDUCATION AND SAFETY NETTING                                │
│                                                                              │
│ REASSURANCE:                                                                 │
│ • This is NOT a stroke                                                       │
│ • Most people (85-95%) make a complete or near-complete recovery            │
│ • Improvement usually begins within 2-3 weeks                                │
│ • Full recovery may take 3-6 months (up to 12 months)                        │
│                                                                              │
│ SAFETY NET - RETURN IF:                                                      │
│ • Weakness affecting other side of face                                      │
│ • Weakness in arms or legs                                                   │
│ • Difficulty swallowing or breathing                                         │
│ • Eye becomes red, painful, or vision changes                                │
│ • No improvement by 3-4 weeks                                                │
│ • Developing blisters in ear (Ramsay Hunt may evolve)                        │
│                                                                              │
│ PRACTICAL ADVICE:                                                            │
│ • May need time off work (sick note provided)                                │
│ • Eating/drinking may be difficult initially (use straw, eat soft foods)    │
│ • Facial exercises may help (mirror exercises)                               │
│ • Psychological impact is normal; support available                          │
└──────────────────────────────────────────────────────────────────────────────┘
                        ↓
┌──────────────────────────────────────────────────────────────────────────────┐
│ STEP 6: FOLLOW-UP                                                            │
│                                                                              │
│ ROUTINE FOLLOW-UP:                                                           │
│ • Review at 2-4 weeks to assess progress                                    │
│ • Document House-Brackmann grade                                            │
│ • Ensure eye care is adequate                                               │
│                                                                              │
│ IF NO RECOVERY BY 3-4 MONTHS:                                               │
│ • Refer to neurology or ENT                                                 │
│ • MRI brain/IAMs with gadolinium to exclude tumour                          │
│ • Electrodiagnostic studies (ENoG, EMG)                                     │
│                                                                              │
│ IF INCOMPLETE RECOVERY:                                                      │
│ • Refer for facial physiotherapy                                            │
│ • Consider botulinum toxin for synkinesis                                   │
│ • Surgical options rarely needed                                            │
└──────────────────────────────────────────────────────────────────────────────┘

Pharmacological Treatment Details

Corticosteroids (First-Line Treatment):

Evidence Summary for Corticosteroids:

• Scottish Bell's Palsy Study (Sullivan et al., NEJM 2007): [6]
  • 496 patients randomised
  • Prednisolone vs. aciclovir vs. both vs. placebo
  • "Complete recovery at 9 months: 94.4% (prednisolone) vs. 81.6% (no prednisolone)"
  • NNT = 9 for one additional complete recovery
• Cochrane Review (2016): [7]
  • Strong evidence supporting corticosteroids
  • Reduces synkinesis and motor synkinesis

Antivirals (NOT Routinely Recommended):

Evidence Summary for Antivirals:

• Cochrane Review (Gagyor et al., 2019): [8]
  • Meta-analysis of 14 trials (2,488 participants)
  • "Antivirals alone: No significant benefit"
  • "Antivirals + corticosteroids: No significant benefit over corticosteroids alone"
  • "Conclusion: Antivirals should NOT be used routinely"

Eye Care Protocol

Special Populations

Pregnancy:

• Bell's palsy 3x more common in pregnancy (especially 3rd trimester and postpartum)
• Prednisolone is safe in pregnancy
• Do not withhold treatment
• Multidisciplinary management with obstetrics

Diabetes Mellitus:

• 2-4x increased risk of Bell's palsy
• Worse prognosis and recovery rates
• Corticosteroids may worsen glycaemic control - monitor and adjust
• Do not withhold treatment; benefits outweigh risks
• Closer follow-up advised

Children:

• Bell's palsy rare less than 10 years; consider alternative diagnoses
• If diagnosed, prednisolone dose adjusted for weight
• Lyme disease more common cause in endemic areas
• Consider Lyme serology routinely in paediatric cases

Immunocompromised Patients:

• Consider broader differential (HIV, infections, malignancy)
• Higher recurrence rates
• May consider antivirals in addition to steroids
• Specialist input advised

Rehabilitation and Long-Term Management

Facial Physiotherapy:

• Indicated for incomplete recovery
• Begins once active movement returns
• Techniques include:
  • Mirror exercises (visual feedback)
  • Mime therapy
  • Neuromuscular retraining
  • EMG biofeedback
• Evidence supports improved outcomes [18]

Synkinesis Management:

• Synkinesis = abnormal co-movement (e.g., eye closes when smiling)
• Develops during aberrant nerve regeneration
• Treatment options:
  • Facial physiotherapy (neuromuscular retraining)
  • Botulinum toxin injection (targeted to overactive muscles)
  • Selective myectomy (rarely)

Surgical Interventions (Rarely Required)

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9. Complications

Acute Complications

Chronic/Sequelae

Synkinesis: Detailed Management

Synkinesis is the most troublesome long-term complication, occurring in 15-20% of patients with incomplete recovery. [18]

Common Synkinesis Patterns:

Management Approach:

1. Facial physiotherapy (first-line)

   • Neuromuscular retraining
   • Small, slow, targeted movements
   • Mirror feedback
   • EMG biofeedback

2. Botulinum toxin (for refractory cases)

   • Targeted injection to overactive muscles
   • Common sites: orbicularis oculi, mentalis, platysma
   • Repeat every 3-4 months
   • Highly effective

3. Selective myectomy (rarely)

   • Surgical removal of overactive muscle
   • Reserved for severe refractory cases

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10. Prognosis and Outcomes

Natural History

Without treatment, approximately 70% of patients with Bell's palsy achieve complete recovery. [6,7] Recovery typically follows this pattern:

Outcomes with Treatment

Prognostic Factors

Favourable Prognosis:

Poor Prognosis:

House-Brackmann Grade and Prognosis

Recovery Timeline

BELL'S PALSY RECOVERY TRAJECTORY

Week 1-2:    [████░░░░░░░░░░░░░░░░] 20% - Some patients begin recovery
Week 3-4:    [████████░░░░░░░░░░░░] 40% - Most show early signs
Week 6-8:    [████████████░░░░░░░░] 60% - Significant improvement
Month 3:     [████████████████░░░░] 80% - Most recovery achieved
Month 6:     [██████████████████░░] 90% - Further gains
Month 9-12:  [████████████████████] 100% - Maximum recovery

Note: Those with incomplete recovery at 12 months are unlikely 
to improve further without intervention.

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11. Evidence and Guidelines

Key Clinical Guidelines

Landmark Trials

1. Scottish Bell's Palsy Study (Sullivan et al., 2007) [6]

2. Cochrane Review: Antivirals for Bell's Palsy (Gagyor et al., 2019) [8]

3. Cochrane Review: Corticosteroids for Bell's Palsy (Madhok et al., 2016) [7]

Evidence Levels for Key Interventions

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12. Exam-Focused Content

Common Exam Questions

Written Examinations (MRCP, Finals):

1. "A 35-year-old woman presents with acute right-sided facial weakness. She cannot close her right eye or raise her right eyebrow. What is the most likely diagnosis and what is your initial management?"

2. "List 5 causes of bilateral facial weakness and the key distinguishing features."

3. "What is the difference between upper and lower motor neuron facial weakness? Explain the anatomical basis."

4. "A patient with Bell's palsy presents with vesicles in the external auditory canal. How does this change your management?"

5. "Discuss the evidence for and against antiviral therapy in Bell's palsy."

OSCE Stations

Station Type: Clinical Examination

• Examine the cranial nerves with focus on the facial nerve
• Grade severity using House-Brackmann scale
• Differentiate UMN from LMN pattern
• Check for Ramsay Hunt syndrome (examine ears)

Station Type: History and Management

• Take history from patient with acute facial weakness
• Explain diagnosis and management plan
• Discuss prognosis and safety-net advice
• Demonstrate eye care technique

Station Type: Communication

• Explain Bell's palsy to a worried patient who thinks they are having a stroke
• Discuss steroid treatment, addressing concerns about side effects
• Counsel regarding incomplete recovery and synkinesis

Viva Points

Viva Point: Opening Statement: "Bell's palsy is an acute, idiopathic, unilateral lower motor neuron facial paralysis characterised by sudden onset weakness affecting all muscles of facial expression on one side, including the forehead. It is the most common cause of acute facial palsy with an incidence of 20-30 per 100,000 per year."

Key Facts to Mention Unprompted:

• Incidence: 20-30 per 100,000/year; lifetime risk 1 in 60
• LMN pattern: forehead IS affected (vs UMN stroke where forehead spared)
• Treatment: Prednisolone 50mg daily for 10 days within 72 hours
• Evidence: Sullivan et al. NEJM 2007 - NNT 9
• Antivirals: NOT recommended (Cochrane 2019)
• Prognosis: 85-95% complete recovery with steroids

Classification System: House-Brackmann Grade I-VI

Management Priorities:

1. Confirm LMN pattern (forehead affected)
2. Exclude Ramsay Hunt (check ears for vesicles)
3. Start prednisolone within 72 hours
4. Eye protection (artificial tears, ointment, taping)
5. Safety-net for red flags

Common Mistakes That Fail Candidates

Model Answer: "Describe Your Approach to Acute Facial Weakness"

"I would approach acute facial weakness systematically:

History: I would establish the onset (acute vs progressive), laterality (unilateral vs bilateral), and ask about associated symptoms including ear pain, vesicles, taste disturbance, hyperacusis, recent viral illness, tick exposure, and any limb weakness or sensory symptoms. I would enquire about risk factors including diabetes and pregnancy.

Examination: I would perform a focused neurological examination. First, I would determine if the pattern is upper or lower motor neuron by testing frontalis - can the patient wrinkle their forehead and raise their eyebrow? In Bell's palsy, an LMN lesion, the forehead is affected. I would grade severity using the House-Brackmann scale. I would examine the external auditory canal and pinna for vesicles, which would indicate Ramsay Hunt syndrome. I would complete a cranial nerve examination and assess limb neurology.

Diagnosis: Bell's palsy is a diagnosis of exclusion. I would confirm LMN pattern, exclude Ramsay Hunt, and ensure there are no red flags such as bilateral weakness, progressive course, or other neurological signs.

Management: For confirmed Bell's palsy, I would initiate prednisolone 50mg once daily for 10 days within 72 hours of onset. This is supported by Level 1a evidence from the Scottish Bell's Palsy Study showing an NNT of 9 for complete recovery. I would NOT prescribe antivirals as the Cochrane review shows no benefit. I would prescribe aggressive eye care: artificial tears every 1-2 hours, lubricating ointment at night, and tape the eyelid closed if incomplete closure. I would safety-net for red flags and arrange follow-up at 2-4 weeks.

If Ramsay Hunt: I would add aciclovir 800mg five times daily for 7 days to the corticosteroid regimen.

Follow-up: If no recovery by 3-4 months, I would refer for MRI to exclude a structural lesion."

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13. Patient/Layperson Explanation

What is Bell's Palsy?

Bell's palsy is a condition that causes sudden weakness of the muscles on one side of your face. It happens when the nerve that controls your facial muscles (called the facial nerve) becomes inflamed and swollen. The exact cause is unknown, but it's thought to be related to a common virus (cold sore virus) that most people carry without problems, which occasionally "wakes up" and causes temporary nerve inflammation.

How Will I Know I Have It?

You may notice:

• One side of your face droops or feels stiff
• You cannot close your eye on the affected side
• You cannot smile or raise your eyebrow normally
• Food or drink may leak from your mouth
• You may have pain around your ear
• Sounds may seem louder than normal
• Your sense of taste may be affected

Important: This is NOT a stroke. In Bell's palsy, your forehead is affected (you can't wrinkle it on the weak side). In a stroke, the forehead usually works normally.

How Is It Treated?

1. Steroid Tablets (Prednisolone)

• These are the main treatment
• You need to start them within 3 days of symptoms beginning
• They significantly improve your chances of full recovery
• Take them for 10 days as prescribed

2. Eye Care (Very Important!)

• Because you can't close your eye properly, it can dry out and get damaged
• Use eye drops (artificial tears) every 1-2 hours during the day
• Use thick eye ointment at night
• Tape your eye closed at night if it won't close fully
• Wear glasses to protect from wind and dust

3. Antiviral Tablets

• These are NOT usually needed for Bell's palsy (despite what you might read online)
• They are only given if you have blisters in your ear (a different condition called Ramsay Hunt syndrome)

What Are My Chances of Recovery?

The good news: Most people with Bell's palsy recover well.

• With steroid treatment started early: 85-95% make a complete recovery
• Without treatment: about 70% recover completely
• You may start to see improvement within 2-3 weeks
• Full recovery can take 3-6 months (sometimes up to 12 months)
• A small number of people have some lasting weakness or unusual movements

When Should I Be Concerned?

Go back to your doctor or seek urgent medical advice if:

• Weakness develops on the OTHER side of your face as well
• You develop weakness in your arms or legs
• Your eye becomes red, painful, or your vision changes
• There's no improvement at all after 3-4 weeks
• You develop blisters or a rash in or around your ear

Tips for Coping

• Take any time off work you need - your doctor can provide a sick note
• Eating and drinking may be tricky at first - use a straw and eat soft foods
• Do gentle facial exercises in front of a mirror once movement starts to return
• It's normal to feel upset or self-conscious - talk to someone if you're struggling
• Support groups like Facial Palsy UK can provide helpful advice

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14. References

Primary Guidelines and Reviews

1. Peitersen E. Bell's palsy: the spontaneous course of 2,500 peripheral facial nerve palsies of different etiologies. Acta Otolaryngol Suppl. 2002;(549):4-30. doi:10.1080/000164802760370736 PMID: 12482166

2. Gilden DH. Bell's palsy. N Engl J Med. 2004;351(13):1323-1331. doi:10.1056/NEJMcp041120 PMID: 15385659

3. Gronseth GS, Paduga R; American Academy of Neurology. Evidence-based guideline update: steroids and antivirals for Bell palsy: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2012;79(22):2209-2213. doi:10.1212/WNL.0b013e318275978c PMID: 23136264

4. Murakami S, Mizobuchi M, Nakashiro Y, Doi T, Hato N, Yanagihara N. Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle. Ann Intern Med. 1996;124(1 Pt 1):27-30. doi:10.7326/0003-4819-124-1_part_1-199601010-00005 PMID: 7503474

5. Furuta Y, Fukuda S, Chida E, et al. Reactivation of herpes simplex virus type 1 in patients with Bell's palsy. J Med Virol. 1998;54(3):162-166. doi:10.1002/(sici)1096-9071(199803)54:3less than 162::aid-jmv3> 3.0.co;2-3 PMID: 9515762

Landmark Trials

6. Sullivan FM, Swan IR, Donnan PT, et al. Early treatment with prednisolone or acyclovir in Bell's palsy. N Engl J Med. 2007;357(16):1598-1607. doi:10.1056/NEJMoa072006 PMID: 17942873

7. Madhok VB, Gagyor I, Daly F, et al. Corticosteroids for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2016;7(7):CD001942. doi:10.1002/14651858.CD001942.pub5 PMID: 27428352

8. Gagyor I, Madhok VB, Daly F, Sullivan F. Antiviral treatment for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2019;9(9):CD001869. doi:10.1002/14651858.CD001869.pub9 PMID: 31486071

Epidemiology and Risk Factors

9. Rowlands S, Hooper R, Hughes R, Burney P. The epidemiology and treatment of Bell's palsy in the UK. Eur J Neurol. 2002;9(1):63-67. doi:10.1046/j.1468-1331.2002.00343.x PMID: 11784378

10. Murakami S, Hato N, Horiuchi J, Honda N, Gyo K, Yanagihara N. Treatment of Ramsay Hunt syndrome with acyclovir-prednisone: significance of early diagnosis and treatment. Ann Neurol. 1997;41(3):353-357. doi:10.1002/ana.410410310 PMID: 9066356

11. Rahman I, Sadiq SA. Ophthalmic management of facial nerve palsy: a review. Surv Ophthalmol. 2007;52(2):121-144. doi:10.1016/j.survophthal.2006.12.009 PMID: 17355852

12. Shmorgun D, Chan WS, Ray JG. Association between Bell's palsy in pregnancy and pre-eclampsia. QJM. 2002;95(6):359-362. doi:10.1093/qjmed/95.6.359 PMID: 12037243

13. Riga M, Kefalas P, Danielides V. The role of diabetes mellitus in the clinical presentation and prognosis of Bell's palsy. J Am Acad Audiol. 2012;23(5):364-370. doi:10.3766/jaaa.23.5.5 PMID: 22533978

14. Yanagihara N. Incidence of Bell's palsy. Ann Otol Rhinol Laryngol Suppl. 1988;137:3-4. doi:10.1177/00034894880970s701 PMID: 3144016

Clinical Features and Examination

15. Adour KK, Byl FM, Hilsinger RL Jr, Kahn ZM, Sheldon MI. The true nature of Bell's palsy: analysis of 1,000 consecutive patients. Laryngoscope. 1978;88(5):787-801. doi:10.1002/lary.1978.88.5.787 PMID: 642672

16. House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985;93(2):146-147. doi:10.1177/019459988509300202 PMID: 3921901

Prognosis and Electrodiagnosis

17. Fisch U. Prognostic value of electrical tests in acute facial paralysis. Am J Otol. 1984;5(6):494-498. PMID: 6393770

18. Teixeira LJ, Valbuza JS, Prado GF. Physical therapy for Bell's palsy (idiopathic facial paralysis). Cochrane Database Syst Rev. 2011;(12):CD006283. doi:10.1002/14651858.CD006283.pub3 PMID: 22161401

Surgical Management

19. Gantz BJ, Rubinstein JT, Gidley P, Woodworth GG. Surgical management of Bell's palsy. Laryngoscope. 1999;109(8):1177-1188. doi:10.1097/00005537-199908000-00001 PMID: 10443817

Additional Resources

20. de Almeida JR, Guyatt GH, Sud S, et al. Management of Bell palsy: clinical practice guideline. CMAJ. 2014;186(12):917-922. doi:10.1503/cmaj.131801 PMID: 24934895

Patient Resources

• Facial Palsy UK: facialpalsy.org.uk
• NICE Clinical Knowledge Summaries: cks.nice.org.uk/topics/bells-palsy
• American Academy of Neurology: aan.com

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate guidelines and specialists for patient care. Evidence and guidelines are current as of the last update date and should be verified against the latest publications.