Bell’s palsy is the most common cause of sudden facial paralysis and can be alarming for patients because its symptoms often resemble those of a stroke. Although the condition typically develops abruptly, most individuals recover fully with appropriate treatment and supportive care.

Understanding the signs of Bell’s palsy, how it differs from other neurological conditions, and the importance of early treatment can help improve outcomes and reduce complications.

What Is Bell’s Palsy?

Bell’s palsy is an acute, isolated paralysis of the facial nerve (cranial nerve VII) that occurs without evidence of brain dysfunction or other systemic neurological disease. It is classified as a peripheral (lower motor neuron) facial nerve palsy, meaning the problem occurs in the facial nerve itself rather than within the brain.

The condition almost always affects one side of the face and develops suddenly, often reaching maximum weakness within hours to days.

Etiology & Risk Factors

The exact cause of Bell’s palsy remains unknown. However, the condition is believed to result from inflammation and swelling of the facial nerve as it travels through the narrow bony canal within the temporal bone. The swollen nerve becomes compressed, impairing its normal function.

Category	Associated Pathogens / Higher Risk Groups
Viral Etiologies	Herpes simplex virus (HSV), Herpes zoster virus (Shingles), Epstein-Barr virus (EBV), Cytomegalovirus (CMV), Human immunodeficiency virus (HIV).
Bacterial Etiologies	Lyme disease (Borrelia burgdorferi), which should be strongly considered in endemic areas.
Risk Factors	Adults, individuals with diabetes mellitus, and pregnant individuals.

Clinical Manifestations

The hallmark feature is sudden weakness or paralysis affecting one side of the face. Because the facial muscles become weak, facial expressions appear noticeably asymmetrical.

• Motor Weakness: Difficulty raising the eyebrow, inability to smile normally, drooping of the face, difficulty closing the affected eyelid, food trapped in the cheek, and accidental inner mouth biting.
• Associated Sensory & Autonomic Signs: Changes in taste sensation, ear pain (otalgia), eye discomfort, tingling or numbness around the cheek/mouth, and reduced tear production causing dry eyes.

What Remains Normal?

One helpful diagnostic feature is that several cranial and peripheral functions remain entirely intact:

• Normal swallowing
• Normal jaw movement for chewing
• Normal extraocular eye movements
• Normal visual fields
• Normal sense of smell

Distinguishing Bell’s Palsy from Stroke & Mimics

Because Bell’s palsy causes sudden facial weakness, it is frequently confused with a stroke. Differentiating peripheral from central lesions on physical exam is vital.

Condition	Forehead Involvement	Associated Neurological Findings
Bell’s Palsy (Peripheral LMN)	Affected: Inability to raise eyebrow or wrinkle forehead on the affected side. Entire half of face is weak.	Isolated facial nerve symptoms. Arm/leg strength, speech, and extraocular movements remain intact.
Stroke (Central UMN)	Spared: Forehead motion intact due to dual/bilateral cortical innervation.	Frequently accompanied by arm/leg weakness, dysarthria/aphasia, visual field defects, or altered consciousness.

Other Conditions That Can Mimic Bell’s Palsy

• Lyme disease (especially in endemic regions)
• Herpes zoster ophthalmicus or Ramsay Hunt syndrome (painful vesicular rash + ear involvement)
• Facial nerve or parotid gland tumors
• Brain tumors, Guillain-Barré syndrome, or basilar meningitis
• Malignant otitis externa or skull base osteomyelitis

Diagnostic Evaluation

Bell’s palsy is primarily a clinical diagnosis. Most patients do not require routine imaging.

• Neuroimaging (CT/MRI): Reserved for diagnostic uncertainty, head trauma, suspected tumor, or atypical focal deficits.
• Electrodiagnostic & Lab Work: Electromyography (EMG) for muscle function evaluation; Lyme serology when exposure/geography indicates.
• Re-evaluation: If symptoms fail to improve after 6 to 8 weeks, further diagnostic workup is required.

Evidence-Based Treatment

1. Corticosteroids

Oral corticosteroids (e.g., prednisone) are the mainstay of treatment. The American Academy of Neurology (AAN) strongly recommends initiating steroids within 72 hours of symptom onset to maximize facial nerve recovery. Benefit is minimal when initiated past this window.

• Dosing Regimen: Prednisone 50–60 mg daily for 5 days, followed by a 5-day taper. (A cumulative dose of ≥450 mg achieves optimal recovery outcomes).

2. Antiviral Medications

Combining corticosteroids with antivirals consistently reduces rates of long-term synkinesis. The AAN assigns antivirals a Level C recommendation as adjunct therapy, noting modest overall recovery gains (risk difference <7%). Antivirals must never be used as monotherapy due to lack of efficacy alone.

• Valacyclovir: 1 g three times daily for 7 days
• Acyclovir: 400 mg five times daily for 10 days

3. Ocular Protection

Because incomplete eyelid closure prevents normal lubrication, preventing corneal drying, irritation, and ulceration is paramount:

• Artificial tears during daytime hours
• Thick lubricating eye ointment at bedtime
• Protective eyewear, moisture chambers, or taping/patching
• Ophthalmology referral for severe incomplete closure

4. Physical Therapy

Facial neuromuscular re-education and targeted physical therapy exercises may benefit patients with incomplete recovery to enhance motor control and manage long-term sequelae.

Prognosis & Recovery

The overall outlook for Bell’s palsy is excellent. Most individuals notice clinical improvement within a few weeks, with complete functional recovery occurring within six months. A small percentage of patients may experience residual weakness, subtle facial asymmetry, or synkinesis.