Facial Nerve Palsy

What the facial nerve does

The facial nerve leaves the brainstem, passes through a narrow bony canal in the skull next to the inner ear, exits just below the ear and fans out through the parotid salivary gland to the face. It controls:

• The muscles of facial expression: forehead, eyelid closure, cheek and mouth
• Tear and saliva production
• Taste from the front two-thirds of the tongue
• A small ear muscle that damps loud sounds

Damage anywhere along this path causes facial nerve palsy. Where it happens shapes the symptoms: a problem inside the bony canal often adds dry eye, taste loss and sensitivity to loud sound (hyperacusis).

Facial nerve palsy vs stroke

Any sudden facial droop should be treated as a possible stroke until a clinician has examined you.

Causes

Bell's palsy

Bell's palsy is the diagnosis when no other cause is found. It accounts for roughly 6 to 7 in 10 cases of one-sided peripheral facial palsy. It is thought to involve viral inflammation and swelling of the nerve inside its bony canal. Risk is higher in pregnancy, especially the third trimester, and with diabetes.

Infections

• Ramsay Hunt syndrome: reactivation of the chickenpox virus (shingles) in the facial nerve. It causes painful blisters in the ear canal, on the outer ear or palate, often with hearing loss, ringing and vertigo. Recovery is less complete than with Bell's palsy.
• Lyme disease: a common cause in children and adults in tick-endemic areas, particularly in summer, and a leading cause of palsy affecting both sides.
• Ear infections: acute otitis media, mastoiditis and cholesteatoma can inflame the nerve as it passes near the middle ear.
• Others: HIV, herpes simplex, and rarely tuberculosis or syphilis.

Injury

Skull base or temporal bone fractures, deep cuts to the cheek, and surgery on the ear or parotid gland can damage the nerve. Weakness that appears immediately after an injury suggests the nerve is cut or crushed, while delayed weakness usually means swelling and has a better outlook.

Tumors

Acoustic neuroma, facial nerve schwannoma, parotid gland cancer and skin cancers spreading along the nerve can cause palsy. Clues are slow onset over weeks, twitching before weakness, a lump near the ear, hearing loss, or no recovery after several months.

Other causes

• Guillain-Barre syndrome and sarcoidosis, which often affect both sides
• Congenital causes: pressure during birth, or Moebius syndrome
• Diabetes and high blood pressure, which increase risk

Bilateral facial nerve palsy

Weakness of both sides is rare and is almost never Bell's palsy. It calls for tests for Lyme disease, Guillain-Barre syndrome, sarcoidosis, HIV, leukemia and lymphoma.

How facial nerve palsy is diagnosed

The doctor checks each part of the face (raising eyebrows, closing the eyes tightly, smiling, puffing the cheeks), looks in the ears and mouth for blisters or infection, tests hearing and examines the other cranial nerves and limbs. Severity is often graded on the House-Brackmann scale from I (normal) to VI (total paralysis).

Further tests depend on the picture:

• Blood tests for Lyme disease, blood sugar, and in some cases HIV or inflammatory markers
• Hearing test when hearing loss or ringing is present
• MRI or CT for slow onset, recurrence, both sides affected, other nerve signs, trauma or no recovery by 3 to 4 months
• Electroneurography (ENoG) and EMG in complete paralysis, to estimate the chance of recovery

Treatment

Protect the eye

When the eyelid cannot close, the cornea dries and can ulcerate. Use lubricating eye drops during the day and ointment at night, wear glasses or a shield outdoors, and tape the eyelid closed for sleep if needed. Eye pain, redness or blurred vision needs prompt review.

Treat the cause

• Bell's palsy: oral steroids started within 72 hours improve recovery. Antivirals may be added in severe cases.
• Ramsay Hunt syndrome: steroids plus antiviral medicine, started as early as possible.
• Lyme disease: antibiotics.
• Ear infection: antibiotics, and sometimes surgery to drain the middle ear or mastoid.
• Trauma or tumor: surgical repair, decompression or removal, often with a nerve graft.

Rehabilitation and long-term options

Facial physical therapy helps retrain movement and reduce synkinesis, where blinking makes the mouth twitch or smiling closes the eye. Botulinum toxin injections can soften synkinesis and tightness. For lasting paralysis, options include an eyelid weight to help closure, nerve transfers, and muscle transfer surgery to restore a smile.

Outlook

Most people with Bell's palsy recover well within 3 to 6 months. Recovery is less complete after Ramsay Hunt syndrome, complete paralysis, trauma that cuts the nerve, or tumors. Early signs of improvement within 3 weeks predict a good recovery.

Frequently asked questions

What is the difference between facial nerve palsy and Bell's palsy?

Facial nerve palsy is the general term for weakness from any damage to the facial nerve. Bell's palsy is one type: sudden facial nerve palsy with no identifiable cause. Doctors diagnose Bell's palsy only after ruling out stroke, infections such as shingles or Lyme disease, injury and tumors.

How long does facial nerve palsy last?

It depends on the cause. Bell's palsy usually starts improving within 2 to 3 weeks and most people recover by 3 to 6 months. Ramsay Hunt syndrome, trauma and tumors often take longer, and recovery may be partial. No improvement after 3 months should prompt imaging and specialist review.

Can stress cause facial nerve palsy?

Stress is not a proven direct cause. Some people notice Bell's palsy after a period of illness, poor sleep or stress, possibly because the immune system lets dormant viruses reactivate. Stress does not explain palsy that develops slowly, recurs, or comes with other symptoms, which need investigation.

What causes facial palsy on both sides?

Bilateral facial palsy is rare and usually has a specific cause, most often Lyme disease, Guillain-Barre syndrome or sarcoidosis, and less often HIV, leukemia or a skull base problem. It needs blood tests, often a lumbar puncture and imaging rather than a diagnosis of Bell's palsy.

Will my face go back to normal?

Most people with Bell's palsy regain normal or near-normal movement. Some are left with mild weakness or synkinesis, which physical therapy and botulinum toxin can improve. When recovery is poor, plastic and reconstructive surgery can restore eye closure and a more symmetrical smile.