facial paralysis, an abnormal condition characterized by the partial or total loss of the functions of the facial muscles or the loss of sensation in the face. It may be caused by disease or by trauma. The degree of paralysis depends on the nerves affected. Brain injury above the facial nerve nucleus usually does not block the innervation of the brow and the forehead muscles. Injury to the nucleus of the facial nerve or injury to its peripheral neurons paralyzes all the ipsilateral facial muscles. See also Bell’s palsy.
