Facial Nerve Palsy

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Facial Nerve Anatomy & Etiology - Path & Problems

  • Anatomy (VII Nerve):
    • Origin: Pons.
    • Course: Pons → IAM → Facial canal (geniculate gang.) → Stylomastoid foramen → Parotid.
    • Functions: Motor (facial expression), Parasymp. (lacrimation, salivation), Taste (ant. 2/3 tongue). Facial nerve and branches
  • Etiology:
    • Idiopathic: Bell's Palsy (most common, ~70%). 📌 Often post-viral (HSV).
    • Infectious: Ramsay Hunt (VZV), Lyme, Otitis Media.
    • Traumatic: Temporal bone #, iatrogenic (e.g., parotid surgery).
    • Neoplastic: Acoustic neuroma, parotid tumors, facial nerve schwannoma.
    • Systemic: Diabetes Mellitus, Guillain-Barré, Sarcoidosis.
  • Path & Problems:
    • Nerve Injury Types: Neuropraxia, Axonotmesis, Neurotmesis (Sunderland).
    • Clinical Issues: Lagophthalmos (exposure keratopathy risk), epiphora, drooling, hyperacusis (stapedius), dysgeusia, synkinesis.

    ⭐ Bell's Palsy: acute, unilateral, idiopathic LMN facial paralysis; most common cause.

Clinical Features & Diagnosis - Droops & Diagnostics

  • Motor Manifestations (Unilateral):

    • Upper Face: ↓ Forehead wrinkling, eyebrow ptosis.
    • Eye: Lagophthalmos (incomplete closure), Bell's phenomenon (upward/outward eye roll on attempted closure). Epiphora or dry eye.
    • Lower Face: Flattened nasolabial fold, drooping angle of mouth, drooling, food accumulation, dysarthria.
    • Ear: Hyperacusis (stapedius palsy), retroauricular pain.
    • Other: Synkinesis (late, aberrant regeneration).
  • Sensory & Autonomic:

    • Taste loss (anterior 2/3 tongue).
    • Altered lacrimation & salivation.
  • Diagnostic Approach:

-   **Key Distinction:**
    +   *LMN Palsy (e.g., Bell's):* Entire ipsilateral face affected (forehead involved).
    +   *UMN Palsy (e.g., Stroke):* Lower face mainly; forehead spared (bilateral UMN innervation).
-   **Grading:** House-Brackmann Scale (Grade I-VI).
-   **Investigations:**
    +   *Topodiagnostic tests (historical, for lesion site):* Schirmer's, stapedial reflex, taste.
    +   *Electrophysiology:* ENoG (Prognostic; >**90%** degen.), EMG (Denervation/reinnervation).
    +   *Imaging (MRI/CT):* For suspected tumor, trauma, atypical cases, or no improvement.

⭐ In LMN facial palsy, the inability to close the eye (lagophthalmos) combined with an intact Bell's phenomenon (upward deviation of the eyeball) is a characteristic finding.

Ocular Management - Shield & Solutions

  • Corneal Protection (Conservative):

    • Lubricating eye drops (artificial tears): Frequent instillation during the day to maintain tear film.
    • Lubricating ointment (e.g., hydroxypropyl methylcellulose): Applied at night to prevent drying.
    • Moisture chambers/goggles: Reduce evaporative loss, especially in windy/dry environments.
    • Taping eyelid shut at night: Simple, effective first-line measure.
  • Medical Treatment:

    • Corticosteroids (Prednisolone): Started within 72 hours of onset for Bell's palsy; improves recovery rates.
    • Antivirals (Acyclovir/Valacyclovir): Added if Ramsay Hunt syndrome suspected (VZV).
    • Botulinum toxin (Botox) injection: Induces protective ptosis; useful for temporary corneal protection when surgery is not yet indicated.
  • Surgical Interventions:

    • Tarsorrhaphy (partial/total): Suturing of eyelids to narrow the palpebral fissure. 📌 Most common surgical procedure for corneal protection in facial palsy.
    • Gold/Platinum eyelid weight implant: Inserted into upper lid; uses gravity for passive lid closure. Preferred for long-term paralysis with cosmetically acceptable results.
    • Lower lid tightening (lateral tarsal strip): Corrects ectropion/lid laxity causing exposure.
    • Temporalis muscle transfer/gracilis free flap: For facial reanimation in irreversible palsy (>12 months).
  • Monitoring:

    • Regular slit-lamp examination for corneal staining (fluorescein).
    • Watch for corneal ulceration - a sight-threatening emergency.
    • Assess Bell's phenomenon - intact upward rotation is protective.

⭐ Tarsorrhaphy is the most reliable surgical method for corneal protection in facial nerve palsy. Gold weight implants offer a cosmetically superior alternative for chronic cases.

High‑Yield Points - ⚡ Biggest Takeaways

  • Bell's palsy (idiopathic) is the most common cause of LMN facial palsy.
  • UMN lesions spare the forehead; LMN lesions cause complete ipsilateral facial weakness.
  • Major ocular risk: exposure keratopathy from lagophthalmos and reduced tear film stability.
  • Management prioritizes corneal protection: lubricants, tarsorrhaphy, gold eyelid weights.
  • Consider Ramsay Hunt syndrome if ear vesicles accompany facial palsy.
  • Lagophthalmos (incomplete eyelid closure) is a critical sign requiring urgent attention.
  • Blink reflex abnormalities (absent or incomplete) further confirm diagnosis and severity of exposure risk.

Practice Questions: Facial Nerve Palsy

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Bilateral facial nerve palsy is seen in

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Flashcards: Facial Nerve Palsy

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Entropion occurs due to Horizontal lid _____, Vertical lid instability, Over-riding of the pretarsal by the preseptal orbicularis during lid closure and Orbital septum laxity

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Entropion occurs due to Horizontal lid _____, Vertical lid instability, Over-riding of the pretarsal by the preseptal orbicularis during lid closure and Orbital septum laxity

laxity

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