FFinalistSouthampton · 2027
Neurology
AKT · Neurology/Cord & peripheral

Bell palsy

Idiopathic (likely viral) lower-motor-neuron CN VII palsy

Overview

An acute, idiopathic (likely post-viral, HSV-linked) LOWER-motor-neuron facial nerve palsy. The key discriminator is that it involves the WHOLE side of the face including the FOREHEAD (forehead-sparing implies an UMN/central cause such as stroke). Early prednisolone improves recovery.

Recognise

  • Acute (over hours–days) unilateral facial weakness involving the FOREHEAD (cannot raise the eyebrow / close the eye)
  • May have post-auricular pain, altered taste, hyperacusis, dry eye
  • Forehead INVOLVED = lower motor neuron (Bell); forehead SPARED = upper motor neuron (stroke)

Red flags

  • Forehead sparing (central cause — stroke), bilateral palsy, other cranial nerves, vesicles (Ramsay Hunt), no recovery → reconsider

Differentials & how to tell them apart

Stroke (UMN facial palsy)forehead SPARED (bilateral cortical innervation of the upper face) + limb signs — an emergency
Ramsay Hunt syndromeherpes-zoster vesicles in the ear/palate + facial palsy → add antivirals
Lyme diseasetick exposure, erythema migrans, may be bilateral
Parotid tumourparotid mass, gradual onset

Investigations

Clinical diagnosis. Examine for forehead sparing (UMN) and a vesicular rash (Ramsay Hunt = herpes zoster); consider Lyme/parotid causes if atypical.

Management

Prednisolone within 72h + meticulous eye protection

  1. 1Confirm it is lower-motor-neuron (forehead involved). Start prednisolone within 72 hours; protect the eye (lubricants, taping at night).Gate: Forehead SPARING means an upper-motor-neuron lesion (e.g. stroke) — that is NOT Bell palsy and needs urgent stroke assessment
  2. 2Add antivirals if Ramsay Hunt/zoster; ophthalmology if incomplete eye closure; most recover over weeks.
Prednisolone — start within 72h — improves recovery
Eye protection (lubricants, tape at night) — prevent exposure keratopathy
Aciclovir — add only if Ramsay Hunt/zoster suspected

Key points

Forehead involved = Bell (LMN); forehead spared = stroke (UMN) — the single most important discriminator. Eye protection prevents exposure keratopathy. Steroids within 72h.

Monitor & prognosis

Recovery, corneal protection/eye health.

Most recover fully within weeks; steroids improve the odds.

Source: NICE CKS Bell palsy