Facial Palsy: Facial nerve paralysis is a common problem that involves the paralysis of any structures innervated by the facial nerve. The pathway of the facial nerve is long and relatively convoluted, and so there are a number of causes that may result in facial nerve paralysis. The most common is Bell’s palsy, a disease of unknown cause that may only be diagnosed by exclusion.

Excerpt from: https://en.wikipedia.org/wiki/Facial_nerve_paralysis