Facial Nerve Palsy: Weakness of the Face — When Is It Bell's Palsy and When Is It Something More Serious?

Sudden weakness of one side of the face — drooping corner of the mouth, inability to close the eye, distorted smile — is a frightening presentation that sends patients and families to emergency departments across Hyderabad. The most common cause is Bell's palsy (idiopathic peripheral facial palsy) — a benign, usually self-limiting condition. But the same presentation can result from stroke, parotid gland tumour, or herpes zoster (Ramsay Hunt syndrome) — each requiring different, urgent management. The clinical examination determines which it is.

The Critical Anatomical Distinction

Lower motor neuron (LMN) facial palsy (peripheral — the nerve itself is damaged): The entire half of the face is weak — including the forehead (the eyebrow cannot be raised on the affected side; the forehead cannot wrinkle). This is because each side's facial nerve controls the entire ipsilateral face. Bell's palsy, Ramsay Hunt syndrome, parotid tumour, and facial nerve trauma all cause LMN palsy.

Upper motor neuron (UMN) facial palsy (central — the cortex or corticobulbar tract is damaged): Only the lower face is weak — the forehead is spared. This is because the forehead motor neurons receive bilateral cortical input (from both hemispheres), so a unilateral cortical stroke cannot fully paralyse the forehead. Central facial palsy from stroke is almost always accompanied by other signs: arm weakness, speech difficulty, UMN signs in the limbs. Forehead sparing in facial weakness = central cause = investigate for stroke urgently.

Ramsay Hunt Syndrome

Reactivation of varicella-zoster virus (VZV) in the geniculate ganglion of the facial nerve. Presents as: LMN facial palsy + painful vesicular rash in the ear canal or pinna + ipsilateral hearing loss and vertigo (if the cochlear and vestibular branches of the 8th nerve are involved). Treated with acyclovir + prednisolone — starting within 72 hours significantly improves outcomes.

Treatment of Bell's Palsy

Prednisolone 50mg daily for 10 days — started within 72 hours of onset. Lubricating eye drops and eye patching at night — the inability to close the eye causes corneal exposure and dryness; keratitis is a preventable complication. 85% of Bell's palsy patients recover fully within 3–6 months. Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.