Bell’s palsy

Bell’s palsy is a sudden weakness or paralysis of the muscles on one side of the face caused by dysfunction of the facial nerve (cranial nerve VII). It often appears overnight and can make one side of the face droop, interfere with eye closure and smiling, and cause drooling or altered taste.

Most cases are idiopathic (no clear cause found), though inflammation and possible viral triggers (including herpes simplex) are suspected. The majority of people recover fully or substantially within weeks to months, especially when treated early with corticosteroids. Eye protection is critical while the eyelid cannot close properly.

Symptoms of Bell’s palsy usually develop rapidly over 48–72 hours and may include:

• Sudden weakness or paralysis on one side of the face
• Facial droop and difficulty making expressions (smiling, raising the eyebrow)
• Drooling
• Pain around the jaw or behind the ear on the affected side
• Increased sensitivity to sound in one ear (hyperacusis)
• Headache
• Loss of taste on the front two-thirds of the tongue
• Changes in tear and saliva production
• Inability to close one eye fully, leading to dryness and irritation

Symptoms are almost always limited to one side. Bilateral facial weakness is rare and warrants broader evaluation.

Bell’s palsy results from inflammation and swelling of the facial nerve as it passes through a narrow bony canal. The exact trigger is often unknown. Reactivation of herpes simplex virus type 1 in the nerve ganglion is a leading hypothesis. Other associated factors include recent upper respiratory infection, diabetes, pregnancy (especially third trimester and early postpartum), and, less often, other infections. When a specific cause is identified (Lyme disease, middle-ear infection, sarcoidosis, tumor), the facial palsy is classified as secondary rather than idiopathic Bell’s palsy.

Risk factors include:

• Pregnancy (particularly late pregnancy and early postpartum)
• Diabetes
• Upper respiratory infection or cold shortly before onset
• Family history in some cases
• Possible higher incidence with certain viral exposures

Possible complications include:

• Corneal drying, abrasion, or ulceration from incomplete eye closure
• Permanent mild facial weakness or asymmetry in a minority of patients
• Synkinesis — involuntary movement of one facial area when another is activated (e.g., eye closure when smiling) during recovery
• Chronic facial pain or spasm (uncommon)
• Psychological distress related to appearance and function during recovery

Most people regain near-normal function; incomplete recovery is more likely with complete paralysis at onset and delayed treatment.

There is no proven way to prevent Bell’s palsy. Managing diabetes and general health may help reduce risk slightly. Prompt treatment after onset improves the chance of full recovery and reduces complications.

Diagnosis is primarily clinical: acute unilateral facial nerve palsy without other central neurologic signs. Clinicians examine the forehead (forehead involvement favors peripheral facial nerve palsy over central stroke), eye closure, mouth movement, and ear/throat structures.

Additional testing is used selectively:

• Lyme serology in endemic areas
• Blood glucose assessment
• Imaging (MRI or CT) if the course is atypical, progression continues beyond a few days, or other neurologic findings are present
• Rarely, electromyography for prognostic information in severe cases

Seek medical care promptly for any sudden facial weakness. Although Bell’s palsy is the most common cause, stroke, Lyme disease, infection, tumor, and other conditions can look similar and need different treatment. Go to the emergency department if facial weakness is accompanied by arm or leg weakness, difficulty speaking, severe headache, vision changes, or altered consciousness — possible stroke signs.

Early treatment improves outcomes:

• Corticosteroids — prednisone (or equivalent) started ideally within 72 hours of onset; the mainstay of therapy
• Antivirals — sometimes added (e.g., valacyclovir) in combination with steroids, though benefit is uncertain and guidelines vary
• Eye care — artificial tears during the day, lubricating ointment and eyelid taping or a moisture chamber at night to protect the cornea; ophthalmology referral if the eye is at risk
• Pain control as needed
• Physical therapy / facial exercises — may help some patients during recovery; evidence is mixed
• Surgery — rarely considered for chronic facial paralysis or severe cases with poor prognosis under specialist care

Most recovery occurs within the first 2–3 months; further improvement can continue up to a year.

While recovering:

• Use lubricating eye drops frequently; apply ointment and protect the eye at night as instructed
• Wear glasses or sunglasses outdoors to reduce drying and irritation
• Eat soft foods and chew on the unaffected side if needed; wipe drool gently
• Take prescribed steroids exactly as directed (do not stop abruptly)
• Perform any recommended facial exercises gently
• Report increasing eye pain, vision change, or lack of any improvement after several weeks

Bring:

• Exact timing of onset and how symptoms have changed
• Recent illnesses, tick exposure, or pregnancy status
• List of medicines and medical conditions (especially diabetes)
• Questions about steroids, eye protection, expected recovery timeline, and warning signs