What area of the face will be affected by a stroke (UMN) that damages CN VII?

What area of the face will be affected by a stroke (UMN) that damages CN VII?

• A. Ipsilateral upper face
• B. Contralateral lower face
• C. Bilateral forehead
• D. Ipsilateral entire face

Answer: (B)

The key idea is how the brain controls facial muscles through corticobulbar projections. The upper part of the face (forehead) receives input from both sides of the brain, while the lower part mainly gets input from the opposite hemisphere. When a stroke damages the upper motor neuron pathways to the facial nerve, the resulting weakness appears on the opposite side—but only in the lower face, because the forehead retains input from the other, intact hemisphere. So the affected area is the contralateral lower face, with the forehead largely spared. This pattern distinguishes central (UMN) facial palsy from a lower motor neuron lesion, which would affect the entire ipsilateral face.

The key idea is how the brain controls facial muscles through corticobulbar projections. The upper part of the face (forehead) receives input from both sides of the brain, while the lower part mainly gets input from the opposite hemisphere. When a stroke damages the upper motor neuron pathways to the facial nerve, the resulting weakness appears on the opposite side—but only in the lower face, because the forehead retains input from the other, intact hemisphere. So the affected area is the contralateral lower face, with the forehead largely spared. This pattern distinguishes central (UMN) facial palsy from a lower motor neuron lesion, which would affect the entire ipsilateral face.