Differentiating Facial Nerve Palsy from Stroke

Key Examination Findings

The American Academy of Otolaryngology-Head and Neck Surgery notes that Bell's palsy causes complete ipsilateral facial weakness, including inability to wrinkle the forehead, while stroke typically spares forehead movement due to bilateral cortical innervation of the upper facial muscles 1, 2
The American Academy of Otolaryngology-Head and Neck Surgery states that Bell's palsy is characterized by complete inability to wrinkle forehead, raise eyebrow, or close eye on affected side, while stroke preserves forehead movement or only mildly affects it 1, 3
The Annals of Emergency Medicine reports that stroke predominantly affects lower face with asymmetric smile and mouth droop, but the pattern may be similar to Bell's palsy in severity 4

The American Academy of Otolaryngology-Head and Neck Surgery suggests that other cranial nerve involvement, such as diplopia, dysphagia, or dizziness, indicates brainstem pathology and is more likely associated with stroke 2
The Annals of Emergency Medicine notes that limb weakness, sensory deficits, speech abnormalities, gaze abnormalities, ataxia, or incoordination are indicative of stroke 4
The American Academy of Otolaryngology-Head and Neck Surgery states that isolated facial weakness with no other neurological deficits is consistent with Bell's palsy 1, 2

The Annals of Emergency Medicine recommends testing forehead function by asking the patient to raise eyebrows and wrinkle forehead, as complete paralysis suggests peripheral (Bell's palsy) 4
The American Academy of Otolaryngology-Head and Neck Surgery suggests that if forehead movement is preserved, it indicates a central lesion (stroke), but does not exclude it if mildly weak 1, 3

The Journal of the American College of Radiology advises that multiple cranial nerve involvement requires immediate MRI regardless of forehead sparing 6, 7
The American Academy of Otolaryngology-Head and Neck Surgery notes that symptoms persisting beyond 2 months warrant MRI to exclude structural lesions 1, 3
The Journal of the American College of Radiology recommends MRI for bilateral facial weakness, as it is extremely rare in Bell's palsy and suggests an alternative diagnosis 6, 7