Differentiation of central from peripheral type of facial palsy

1. Big picture

Facial palsy is a classic localization question. The examiner usually wants you to decide:

Is the lesion above the facial nucleus? → Central / upper motor neuron facial palsy

or

Is the lesion in the facial nucleus, facial fascicle, or facial nerve? → Peripheral / lower motor neuron facial palsy

The key clinical rule:

Central facial palsy spares the forehead. Peripheral facial palsy involves the whole ipsilateral half of the face.

This happens because the upper face has bilateral supranuclear innervation, while the lower face mainly receives contralateral supranuclear innervation.