Summary
Bell’s palsy is differentiated from an acute stroke mainly by the pattern of facial weakness. In Bell’s palsy, a lower motor neuron lesion, the entire ipsilateral face—including the forehead—is affected, whereas in a typical stroke (an upper motor neuron lesion), the forehead is spared due to bilateral cortical innervation. A careful neuro exam assessing for additional neurological deficits (e.g., limb weakness, dysarthria, sensory loss) further supports a stroke if present.
At-a-glance
| Feature | Bell’s Palsy (Peripheral LMN) | Stroke (Central UMN) |
|---|
| Facial involvement | Entire half; inability to wrinkle forehead | Lower face predominantly; forehead spared |
| Associated deficits | Usually isolated facial nerve impairment | Often accompanied by other neuro deficits |
| Onset pattern | Acute over hours to 72 hours | Hyperacute, potentially minutes |
| Additional symptoms | Altered taste, dry eye, hyperacusis | Other cranial nerve or motor/sensory deficits |
Bell’s palsy presents with complete unilateral facial paralysis, including the inability to wrinkle the forehead, due to involvement of the entire facial nerve ^1. In contrast, a central facial palsy seen with stroke typically spares the upper face because of its bilateral innervation ^2. Assessing for concomitant signs such as limb weakness, dysarthria, or other cranial nerve deficits helps differentiate an acute stroke from an isolated Bell’s palsy ^3.