Bell palsy — LMN diagnosis, steroid window and corneal protection

(a) Diagnosis and forehead anatomy. This is an acute lower motor neurone (peripheral) facial (CN VII) palsy — clinically Bell palsy once secondary causes are excluded at the bedside. Forehead involvement indicates an LMN lesion because frontalis receives bilateral cortical innervation: a unilateral upper motor neurone (cortical stroke) lesion spares the forehead, whereas an LMN lesion after the facial nucleus denervates all ipsilateral facial muscles including frontalis.^[3]

(b) Drugs. Start oral prednis(ol)one ~50–60 mg daily for 5 days then taper, ideally within 72 hours of onset (Sullivan 2007; Cochrane supports corticosteroid benefit).^[1][2] Antivirals alone do not improve typical Bell palsy and add little when combined with steroid for idiopathic disease. Add high-dose antiviral (aciclovir 800 mg five times daily or valaciclovir 1 g TDS) plus steroid if Ramsay Hunt (vesicles, severe otalgia, hearing loss).^[4]

(c) Eye care and safety-net. Incomplete eye closure risks exposure keratitis: preservative-free lubricant drops by day, ointment and eyelid taping or a moisture chamber at night; urgent ophthalmology if the cornea remains unprotected. Written advice to return for new limb weakness, vesicles, visual change or fever; GP/ENT review at 3–4 weeks; ~70% full recovery expected with timely care.^[3][5]