Bell's Palsy (Facial nerve palsy)

Related Subjects: |Bell's (Facial Nerve) palsy |Ramsay Hunt syndrome |Facial nerve anatomy

😮 Bell's Palsy is an idiopathic, acute, unilateral lower motor neuron (LMN) facial nerve palsy. ⚡ Develops rapidly (within 72 hours) and does not progress further after that. ❌ A gradually progressive palsy is not Bell’s Palsy. Ear and facial pain are common and do not necessarily imply middle ear disease.

📌 About

• Often mistaken for stroke, but Bell’s Palsy involves the entire face including the forehead (LMN lesion).
• Named after Sir Charles Bell (1774–1842).
• Incidence: 15–30 per 100,000 people annually; men and women equally affected.

🧠 Anatomy of CN VII

• Mixed cranial nerve (motor > sensory > parasympathetic).
• Courses through the temporal bone in a narrow canal → vulnerable to inflammation and compression.

🦠 Aetiology

• Mostly idiopathic, but thought to be post-viral (HSV, VZV).
• When caused by VZV (with vesicles) → Ramsay Hunt Syndrome.

🤒 Clinical Features

• Rapid unilateral facial weakness, maximal within hours to days.
• Ear pain on affected side.
• Weakness involves forehead, eye, and mouth (LMN pattern).
• Other features: altered taste (ant. 2/3 tongue), hyperacusis, reduced tear production, impaired corneal reflex.
• Bell’s sign: Eye rolls up/out when attempting closure.
• Look carefully for vesicles (Ramsay Hunt) or other CN palsies (e.g. VI nerve with pontine lesions).

🚫 Key Exclusions

• Other neurological deficits.
• Abnormal ear/throat exam (vesicles, tumours, OM).
• Neck or parotid masses.
• Consider Lyme disease, sarcoid, skull base pathology if atypical.

🧑‍⚕️ Examination Notes

• VII is primarily motor, but patients may report “numbness” despite intact sensation.
• Tests:
  • Ask to smile/show teeth → affected side droops.
  • Ask to close eyes → incomplete closure, Bell’s sign visible.
  • Forehead wrinkling reduced on affected side.

🦠 HIV: Facial nerve palsy is ~100× more common in HIV patients than immunocompetent patients.

🩺 Differentials

• Parotid tumour (often malignant).
• Lyme disease (bilateral LMN VII, rash/joint pain).
• Sarcoidosis (Heerfordt’s syndrome, hilar lymphadenopathy).
• Guillain-Barré (bilateral LMN VII + limb paraesthesia).
• Stroke: UMN → forehead spared.
• Pontine stroke: LMN VII + VI palsy ± contralateral weakness.

🔎 Investigations

• Primarily clinical diagnosis.
• Bloods: FBC, U&E, glucose, ESR, TFTs if atypical.
• MRI: Consider if atypical (pons lesion, tumour, geniculate ganglion enhancement).
• Nerve conduction/EMG: Occasionally useful to grade nerve damage.

📊 House–Brackmann Classification

• I – Normal
• II – Mild dysfunction (minimal asymmetry)
• III – Moderate dysfunction (incomplete smile, but eye closure possible)
• IV – Severe dysfunction (obvious weakness, incomplete eye closure)
• V – Minimal movement
• VI – Complete paralysis

⚠️ Complications

• Residual facial weakness.
• Synkinesis (involuntary movements, e.g. eye closes when smiling).
• Hearing loss or neuropathic pain.

💊 Management

• Steroids: If onset <72h, Prednisolone 60 mg daily (taper over 10 days). → Increases recovery rate (81.6% → 94.4%). Avoid/adjust in pregnancy, diabetes, glaucoma, ulcers, elderly with osteoporosis.
• Antivirals: Only if vesicles present (Ramsay Hunt) → Aciclovir 800 mg 5×/day ×7 days.
• Eye care: Artificial tears, Lacrilube at night, tape/patch if cornea exposed.
• Recovery: Usually within 3–6 months.

📞 Referral

• Uncertain diagnosis, recurrent, or bilateral cases.
• Urgent ophthalmology if cornea exposed.
• ENT if no improvement at 1 month, or persistent weakness >6–9 months (may need plastics).

📉 Poor Prognostic Factors

• Complete palsy with no recovery by 3 weeks.
• Age >60, severe pain, Ramsay Hunt, diabetes, hypertension, pregnancy.
• Severe nerve degeneration on EMG.

📚 References

• BMJ Review: Bell's Palsy