Facial nerve an incorrectly placed dental local-anesthetic (Inferior alveolar nerve block). Although giving the appearance of a hemi-plegic stroke, effects dissipate with the drug. When the facial nerve is permanently damaged due to a birth defect, trauma, or other disorder, surgery including a cross facial nerve graft or masseteric facial nerve transfer may be performed to help regain facial movement. Facial nerve decompression surgery is also sometimes carried out in certain cases of facial nerve compression. Voluntary facial movements, such as wrinkling the brow, showing teeth, frowning, closing the eyes tightly (inability to do so is called lagophthalmos) , pursing the lips
Facial expression have even shown that there are similarities between species in how emotions are expressed. Research has shown that chimpanzees are able to communicate many of the same facial expressions as humans through the complex movements of the facial muscles. In fact, the facial cues were so similar that Ekman's Facial Action Coding System could be applied to the chimps in evaluating their expressions. Of course, differences between the species' physical facial properties, such as white sclera and everted lips in chimps, would mean that some expressions could not be compared. Similarly, Darwin observed that infants' method of expression for certain