How do you differentiate between Bell's palsy and stroke in a child presenting with sudden onset of facial weakness?

Differentiating Bell's Palsy from Stroke in Children

The key distinguishing feature is forehead involvement: Bell's palsy causes complete hemifacial weakness including the forehead, while stroke causes central facial weakness that spares the forehead due to bilateral cortical innervation of the upper facial muscles. 1, 2, 3

Primary Clinical Distinction

Forehead Function is the Critical Differentiator:

• Bell's palsy: The child cannot wrinkle the forehead, close the eye, or raise the eyebrow on the affected side because the peripheral facial nerve lesion affects all ipsilateral facial muscles 3
• Stroke: The child can still wrinkle the forehead and raise the eyebrow on the affected side because upper facial muscles receive bilateral cortical innervation, but lower facial weakness is present 2, 3

Associated Neurologic Findings

Stroke typically presents with additional neurologic symptoms that are absent in Bell's palsy:

• Dizziness, dysphagia (swallowing difficulty), or diplopia (double vision) suggest stroke rather than Bell's palsy 3
• Weakness in extremities, speech difficulties beyond facial weakness, or altered mental status indicate stroke 3
• Involvement of other cranial nerves excludes Bell's palsy and suggests central pathology 3
• Document function of all cranial nerves VII-XII to exclude stroke and other central causes 3

Temporal Profile

Onset timing helps differentiate these conditions:

• Bell's palsy develops rapidly but progresses over up to 72 hours 1, 3
• Stroke typically has more sudden onset with maximal deficit at presentation 4, 5

Additional Clinical Features Supporting Bell's Palsy

These features suggest Bell's palsy rather than stroke:

• Ipsilateral ear or facial pain preceding or accompanying the weakness 3
• Taste disturbance from the anterior two-thirds of the tongue 3
• Hyperacusis (increased sensitivity to sound) 3
• Dry eye or excessive tearing 3
• Sagging of the eyelid or corner of mouth with drooling 3, 6

Critical Pitfalls to Avoid

Do not assume all isolated facial weakness is Bell's palsy:

• Rare pontine infarcts can present as isolated facial palsy mimicking Bell's palsy, particularly in patients with vascular risk factors like diabetes or hypertension 4, 5
• These dorsal pontine strokes are challenging to identify on imaging due to small size (as small as 4 mm) 4, 5
• Always consider stroke in children with vascular risk factors, even with isolated facial weakness 5

When to Obtain Imaging

Imaging is not routinely recommended for typical Bell's palsy presentations, but should be obtained when:

• Other neurologic findings are present at any point 1, 3
• The presentation is atypical (bilateral involvement, recurrent episodes, or no forehead involvement) 2, 3
• Vascular risk factors are present with acute onset 3
• The child has diabetes, hypertension, or other stroke risk factors 4, 5

Diagnostic Approach Algorithm

1. Assess forehead function: Can the child wrinkle their forehead on the affected side? If yes, suspect stroke; if no, consider Bell's palsy 2, 3

2. Examine all other cranial nerves: Any additional cranial nerve involvement excludes Bell's palsy 3

3. Check for limb weakness, speech difficulties, or altered consciousness: Presence of these indicates stroke 3

4. Assess for associated symptoms: Ear pain, taste changes, and hyperacusis support Bell's palsy 3

5. Consider risk factors: Diabetes, hypertension, and pregnancy increase risk for both conditions but should raise suspicion for stroke if present 4, 5

6. Obtain MRI if atypical features present: New or worsening neurologic findings, bilateral involvement, or vascular risk factors warrant imaging 1, 3

Special Consideration for Bilateral Facial Weakness

Bilateral facial palsy is extremely rare in Bell's palsy and should immediately trigger investigation for alternative diagnoses:

• Guillain-Barré syndrome 2, 3
• Lyme disease 2, 7
• Sarcoidosis 2, 7
• Do not accept bilateral presentation as idiopathic Bell's palsy 2, 7