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EN4.16 | Facial Nerve Palsy — SDL Guide (Part 2)
Diagnosis and Differential Diagnosis
Bell's palsy is the commonest cause of acute LMN facial palsy, but it is a diagnosis of exclusion that can only be made after secondary causes have been considered and excluded. The approach is systematic: confirm LMN pattern, take a thorough history including ear symptoms and skin lesions, examine the ear carefully (otoscopy), palpate the parotid, and assess the rest of the cranial nerves. Any atypical feature mandates imaging. The diagnostic approach is essentially a structured search for red flags that would require further investigation — the absence of all red flags in an otherwise healthy patient with an acute LMN palsy, normal ear examination, and an intact tympanic membrane is what establishes Bell's palsy as the working diagnosis, to be confirmed by the expected spontaneous recovery trajectory.
Features that make Bell's palsy the likely diagnosis:
- Acute onset, maximum at 48–72 hours
SELF-CHECK
A 35-year-old woman presents with a 3-day history of complete right-sided facial paralysis (HB VI). The ear canal shows a cluster of painful herpetiform vesicles. She reports a blocked feeling in the right ear. Rinne and Weber tests show Rinne positive bilaterally and Weber central. The immediate management should include:
A. Prednisolone alone — antiviral therapy adds no benefit
B. Prednisolone AND antiviral therapy (acyclovir or valaciclovir) plus urgent eye care
C. Emergency surgery to decompress the facial nerve
D. No treatment — Ramsay Hunt syndrome recovers spontaneously without intervention
Reveal Answer
Answer: B. Prednisolone AND antiviral therapy (acyclovir or valaciclovir) plus urgent eye care
This is Ramsay Hunt syndrome (VZV reactivation — vesicles in ear + facial palsy). Management combines: (1) high-dose prednisolone (50 mg/day, tapering over 10 days), (2) antiviral therapy (acyclovir 800 mg 5×/day or valaciclovir 1g tds for 7 days) — the evidence for adding antivirals is stronger for Ramsay Hunt than for Bell's palsy because VZV replication is active, and (3) urgent eye care (lubricating drops, tape the eye at night) to prevent corneal exposure keratopathy. Emergency decompression surgery is not indicated acutely unless there is complete degeneration on ENoG. Ramsay Hunt has a worse prognosis than Bell's palsy; antiviral therapy is standard care.
Principles of Management
Management of facial nerve palsy depends on the underlying cause, the degree of paralysis (House-Brackmann grade), and the time since onset. The two immediate priorities in any complete facial palsy are eye protection (to prevent corneal exposure keratopathy) and treatment of any modifiable cause.
1. Eye care (immediate — all complete facial palsies)
The paralysed eyelid creates the most acute risk in facial nerve palsy. In facial nerve palsy, the orbicularis oculi muscle cannot close the eye, leaving the cornea exposed to drying, microtrauma, and bacterial contamination with each blink. The degree of risk correlates with HB grade: HB IV–VI require active corneal protection immediately. Treatment is straightforward and inexpensive — lubricating drops and ointment — but it must be prescribed at the first visit, not deferred. A patient who cannot close the eye is at risk of corneal ulceration from exposure and drying within hours. Mandatory eye care:
- Lubricating eye drops (hypromellose or similar) during the day, every 1–2 hours
CLINICAL PEARL
The most dangerous short-term complication of facial nerve palsy is corneal exposure keratopathy — not the facial cosmetic deficit. Every patient with a facial palsy and incomplete eye closure must leave the consultation with lubricating drops and an ointment prescription and an instruction to return immediately if the eye becomes red, painful, or photophobic. This is a same-session imperative. Prescribing prednisolone but forgetting the eye care is a common and potentially sight-threatening oversight. Additionally, in any facial palsy that is progressing slowly over weeks, or associated with a parotid mass: think malignancy and image before treating empirically as Bell's palsy.
Self-Assessment: Facial Nerve Palsy
Facial nerve palsy requires integration of three domains: anatomy (the intratemporal course and its branches), clinical examination (UMN vs LMN bedside distinction, House-Brackmann grading, topognostic tests), and management (eye care as an immediate priority, evidence-based medical treatment for Bell's palsy and Ramsay Hunt, surgical decompression criteria). These three domains are not independent — the anatomical level of the lesion determines both the clinical deficit pattern and the management choice, making anatomy the logical starting point for self-assessment. Before answering the questions below, try to sketch mentally the intratemporal course of the facial nerve, naming each branch and the function it carries — this anatomical map is the foundation of topognostic reasoning and is a common examination viva topic that rewards active recall.
Key concept checks:
- What is the bedside test that distinguishes UMN from LMN facial palsy, and what is the anatomical basis?
SELF-CHECK
A 60-year-old diabetic man presents with complete right LMN facial palsy of 2-day duration (HB VI). He has no vesicles and normal otoscopy. The correct first-line management is:
A. Antiviral therapy alone (acyclovir) — steroids are contraindicated in diabetes
B. Prednisolone 50 mg/day for 10 days plus eye care; antivirals optional or added per guideline
C. Urgent surgical decompression — complete paralysis always requires surgery
D. Observation only — Bell's palsy at this grade always recovers spontaneously
Reveal Answer
Answer: B. Prednisolone 50 mg/day for 10 days plus eye care; antivirals optional or added per guideline
For Bell's palsy presenting within 72 hours with complete paralysis (HB VI), the evidence-based first-line treatment is prednisolone 50 mg/day for 10 days. Diabetes is a relative concern (steroids raise blood glucose) but is NOT a contraindication — blood glucose should be monitored and doses adjusted if needed. Acyclovir alone is not better than placebo for Bell's palsy; antiviral is added to steroids, not used instead. Surgical decompression is not first-line — it is reserved for cases with >90% ENoG degeneration at day 14 in select centres. Bell's palsy with HB VI has a 70–85% chance of complete recovery with treatment but is NOT guaranteed to recover without it — withholding treatment in a young patient would be suboptimal. Eye care is mandatory at every grade where eye closure is incomplete.