Bell's Palsy HSV-1 — SCE Infectious Diseases MCQ

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EasyCNS InfectionBell's Palsy HSV-1SCE Infectious Diseases

A 40-year-old man presents with acute-onset unilateral facial weakness (lower motor neurone pattern). He has no rash, no tick exposure history, and no travel history. Lyme serology is negative. What is the most common cause of acute unilateral LMN facial palsy?

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Correct answer: B — Bell's palsy (idiopathic — thought to be HSV-1 reactivation in the geniculate ganglion in most cases)

Bell's palsy is the most common cause of acute unilateral LMN facial palsy (~70% of cases). It is thought to be caused by HSV-1 reactivation in the geniculate ganglion causing inflammation and oedema of cranial nerve VII within the facial canal. Treatment (if presenting within 72 hours): Prednisolone 25 mg BD for 10 days ± Aciclovir (evidence for antivirals is weaker). Lyme disease should be considered if: tick exposure, endemic area, bilateral facial palsy, or other neurological features. Ramsay Hunt (VZV — vesicular rash in the ear canal/auricle + facial palsy) requires Valaciclovir plus Prednisolone.

Reference: NICE CKS 2024 – Bell's palsy; Cochrane 2010 – Corticosteroids for Bell's palsy