A lesion involving upper motor neuron of facial nerve manifests as

The facial muscles are innervated by the facial nerve. Damage to the facial nerve in the internal acoustic meatus (by a tumor), in the middle ear (by infection or operation), in the facial nerve canal (perineuritis, Bell's palsy), or in the parotid gland (by a tumor) or caused by lacerations of the face will cause distoion of the face, with drooping of the lower eyelid, and the angle of the mouth will sag on the affected side. This is essentially a lower motor neuron lesion. Check voluntary movement of the upper pa of the face on the affected side: in supranuclear lesions such as a coical stroke (upper motor neuron; above the facial nucleus in the pons), the upper third of the face is spared while the lower two thirds are paralyzed. The orbicularis, frontalis, and corrugator muscles are innervated bilaterally, which explains the pattern of facial paralysis in these cases