What are the key differences in diagnosis and treatment between Bell's Palsy and a cerebrovascular accident (CVA) (stroke) in patients presenting with facial weakness?

Distinguishing Bell's Palsy from Stroke (CVA)

Critical Distinguishing Feature: Forehead Involvement

The single most important clinical feature to differentiate Bell's palsy from stroke is forehead involvement—Bell's palsy affects the entire ipsilateral face including the forehead, while stroke spares forehead function due to bilateral cortical innervation of upper facial muscles. 1, 2

Key Diagnostic Differences

Bell's Palsy Presentation

• Complete hemifacial weakness involving both upper and lower face, with inability to raise eyebrow, close eye, or wrinkle forehead on affected side 1, 2
• Rapid onset within 72 hours of symptom development 1, 2
• Isolated facial nerve dysfunction without other neurological deficits 1, 2
• May include ipsilateral ear/facial pain, taste disturbance on anterior two-thirds of tongue, hyperacusis, and dry eye 1, 2
• Bilateral facial weakness is extremely rare and should prompt investigation for alternative diagnoses 2

Stroke (CVA) Presentation

• Forehead sparing—patient can raise eyebrow and wrinkle forehead on affected side because upper facial muscles receive bilateral cortical innervation 1, 2
• Additional neurological symptoms including limb weakness, sensory changes, diplopia, vertigo, dysphagia, dysarthria, altered mental status, or other cranial nerve involvement 2, 3, 4
• Presence of vascular risk factors with acute onset 2
• Contralateral motor or sensory deficits in face, arm, or leg 2, 4
• Language disturbances (aphasia/anomia) indicate cortical involvement and definitively exclude Bell's palsy 3

Diagnostic Approach Algorithm

Step 1: Assess Forehead Function

• Ask patient to raise eyebrows and wrinkle forehead 1, 2
• If forehead is spared → suspect stroke, proceed to stroke protocol 2
• If forehead is involved → proceed to Step 2 1, 2

Step 2: Screen for Additional Neurological Deficits

• Evaluate all cranial nerves (especially III, IV, VI, IX, X, XI, XII) 2, 3
• Test limb strength, sensation, coordination 2, 3
• Assess speech, language, and swallowing 2, 3, 4
• If ANY other neurological findings present → suspect stroke or central pathology, obtain urgent imaging 2, 3, 4
• If isolated facial weakness only → proceed to Step 3 1, 2

Step 3: Evaluate Onset and Associated Symptoms

• Confirm onset within 72 hours 1, 2
• Check for Bell's palsy-associated features: ear pain, taste changes, hyperacusis, dry eye 1, 2
• If atypical features present (progressive weakness beyond 3 weeks, recurrent paralysis, isolated branch involvement) → obtain MRI with contrast 1, 2
• If typical presentation → diagnose Bell's palsy, no imaging needed 1, 2

Imaging Recommendations

Bell's Palsy

• Routine imaging NOT recommended for typical presentations 1, 2
• MRI with and without contrast indicated only for: atypical features, no recovery after 3 months, progressive weakness, recurrent paralysis, or other cranial nerve involvement 1, 2

Suspected Stroke

• Immediate CT or MRI required to evaluate for cerebrovascular event 2, 3
• Activate stroke protocol if within therapeutic window 3

Treatment Differences

Bell's Palsy Management

• Oral corticosteroids within 72 hours: prednisolone 50 mg daily for 10 days OR prednisone 60 mg daily for 5 days with 5-day taper 1, 2
• Evidence shows 83% recovery at 3 months with prednisolone versus 63.6% with placebo 1, 2
• Antiviral monotherapy should NEVER be prescribed—ineffective alone 1, 2
• Optional combination therapy: antivirals plus steroids may provide small additional benefit (96.5% versus 89.7% complete recovery) 2
• Mandatory eye protection: lubricating drops every 1-2 hours while awake, ointment at bedtime, eye taping/patching, sunglasses outdoors 1, 2

Stroke Management

• Immediate stroke protocol activation 3
• Thrombolytic therapy or thrombectomy if within therapeutic window 3
• No role for corticosteroids in acute stroke management 3

Critical Red Flags Requiring Urgent Evaluation

Any of the following mandate immediate stroke workup, NOT Bell's palsy treatment: 2, 3, 4

• Forehead sparing with preserved upper facial function 2
• Diplopia, gaze palsy, or nystagmus 2, 4
• Dysphagia or dysarthria 2, 4
• Limb weakness or sensory deficits 2, 3
• Language disturbances (aphasia, anomia) 3
• Altered mental status or confusion 2, 3
• Vertigo with other neurological signs 2, 4

Common Diagnostic Pitfalls

• Assuming all facial weakness is Bell's palsy—rare pontine infarcts can present as isolated facial palsy mimicking Bell's palsy, but careful examination reveals subtle additional findings 4, 5
• Missing forehead assessment—this single examination finding is the most reliable distinguishing feature 1, 2
• Overlooking subtle additional cranial nerve involvement—document function of all cranial nerves systematically 2, 3
• Failing to recognize that hemifacial paresthesia with anomia indicates stroke, not Bell's palsy recurrence 3
• Delaying imaging in atypical presentations—progressive weakness beyond expected timeline, bilateral involvement, or recurrent episodes require MRI 1, 2

Follow-Up Considerations

Bell's Palsy

• Reassess at 1-2 weeks to monitor recovery and reinforce eye protection 1
• Mandatory reassessment at 3 months if incomplete recovery—refer to facial nerve specialist 1, 2
• Approximately 70% with complete paralysis recover fully within 6 months; 94% with incomplete paralysis recover 1

Post-Stroke

• Ongoing neurological monitoring and rehabilitation 3
• Secondary stroke prevention measures 3