Muscles which are affected and its actions:
Frontalis - elevates the eyebrows and wrinkles the forehead
orbicularis oculi - closes the eyelids
orbicularis oris - purses the lips
Buccinator - pulls the corner of mouth laterally; presses the cheek against the teeth
platysma muscle - draws the corners of the mouth down; it aids in depression of the mandible
Mechanism of his muscle weakness:
Bell’s palsy is an unexplained episode of facial muscle weakness or paralysis. It results from damage to the facial nerve (the 7th cranial nerve, the nerve that controls facial muscles). It usually only affects the muscles on one side of the face.
Other symptoms the patient could exhibit as a result of facial muscle weakness
-eyelids cannot fully close on the affected side
-drooling
-headache
-difficulty speaking, eating or drinking
-loss of taste
-pain around the jaw / in or behind the ear on the affected side