First of all, it should be pointed out that, due to the anatomy of the facial nerve, the symptoms of a partial or complete functional failure of this nerve can be differently pronounced.
A complete paralysis of the facial nerve is a peripheral or central facial nerve paresis that is accompanied by a complete loss of function of the mimic muscles. It therefore affects frowning, eyelid closure, elevation of the corner of the mouth and the entire emotional expression of the affected side. Furthermore, a loss of taste sensation or a reduction of hearing (hypacusis) can also occur in the course of a complete facial nerve palsy. Approximately 70% of patients show complete paralysis of the facial nerve. It should be emphasized that the result of the clinical examination may differ from the results of electrophysiological examinations, such as the assessment of the electrical activity of a muscle (electromyography; EMG). Accordingly, an EMG examination can also provide evidence of electrical activity of the facial muscles and the continuity of the facial nerve preserved in this way even in the case of a clinical diagnosis of complete facial nerve palsy.
Incomplete facial nerve palsy can be incomplete in various respects. On the one hand, all target muscles of the facial nerve may be affected, but these may not be completely without function, but only weakened and thus partially functional. On the other hand, parts of the facial nerve may be affected, such as in isolated paralysis of the corner of the mouth lifter. Furthermore, the extent of the paralysis can increase in the case of facial nerve paresis that occurs without a recognizable reason (Bell's palsy; idiopathic facial nerve paralysis). The maximum then usually appears on the second day.