Sudden one-sided facial weakness can be Bell's palsy — or it can be stroke, tumour, or Ramsay Hunt syndrome. Dr. Anand Karnam explains the critical clinical distinctions that determine the right diagnosis and treatment.
Key Points
- Bell's palsy (idiopathic facial nerve palsy) is the most common cause — probable viral inflammation of the 7th nerve.
- Key distinction from stroke: Bell's palsy affects the forehead (cannot raise eyebrow); central facial palsy (stroke) spares it.
- Ramsay Hunt syndrome (herpes zoster affecting the ear and facial nerve) is more severe with poorer prognosis.
- Eye protection is critical — lubricating drops, eye tape at night, and glasses during the day to prevent corneal injury.
- Prednisolone started within 72 hours of Bell's palsy onset gives >90% full recovery rate.
72 hrs
window for starting steroids in Bell's palsy for maximum benefit
Source: Cochrane
90%+
full recovery rate for Bell's palsy treated with prednisolone
Source: NHS
25 per 100K
annual incidence of Bell's palsy — affects all ages equally
Source: NCBI
"The first thing I do with facial palsy is look at the forehead. If the patient cannot wrinkle their forehead on the weak side — it's Bell's palsy. If the forehead is spared, I'm thinking about a stroke in the motor cortex. Same symptom, completely different emergency level."
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.
Dr. Anand Karnam
DrNB Neurology · Sri Anand CNC, Chanda Nagar Hyderabad · Sri Anand Child and Neuro Center
DrNB-qualified Neurologist, Fellow of the World Headache Society (FWHS), and Headache Specialist with 12+ years of experience treating epilepsy, stroke, migraine, and movement disorders. Practices at Sri Anand Child and Neuro Center, Chanda Nagar, Hyderabad.
References & Sources
- 1.Bell's Palsy — NCBI StatPearls — NCBI StatPearls
- 2.Bell's Palsy — NHS — NHS UK
- 3.Bell's Palsy — NIH MedlinePlus — NIH MedlinePlus
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