The UMN Facial pasly is the supranuclear palsy, charectaristically involves only the ipsilateral lower half of the face ( Upper half has bilateral supply)
It is of two types.
1. Mimetic Facial Palsy: Also called emotional facial paresis, characterized by clinically identifiable facial palsy on mimetic movements like smiling, weeping e.t.c. There is no facial paresis with voluntary facial expression like showing teeth and closing eyes.
This is seen with lesions involving the contralateral frontal lobe anterior to the precentral gyrus, SMA, frontal lobe white matter, Mesial temporal lobe, insula, thalamus and subthalamus and post encephalitic parkinsonism.
2. Volitional Facial Palsy: The facial palsy is most marked on voluntary contraction of muscles and less so on mimetic movements.
This is seen with lesions interrupting the ipsilateral corticobulbar fibers from the lower precentral gyrus, internalcapsule, cerebral peduncle, upper pons ( above facial nucleus)
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