The muscles affected by the Bell’s Palsy include: (1) Frontalis, (2) Orbicularis Oculi, (3) Orbicularis Oris, (4) Buccinator, and (5) Platysma Muscles. The condition, Bell’s Palsy, is a unilateral paralysis of the muscles of facial expression due to damages of the facial (VII) nerve. The possible causes of this are the following: (1) inflammation of the nerve due to an ear infection, (2) ear surgery that damages the facial nerse, or (3) infection by the herpes simplex virus. Other symptoms that a patient with Bell’s Palsy are: (1) drooling, (2) difficulty in swallowing, and (3) inability to wrinkle the forehead, close the eye, or pucker the lips on the affected side.
Here is the action of each muscle affected respectively: (1) Frontalis - Draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally, (2) Orbicularis Oculi - Closes the eye, (3) Orbicularis Oris - Closes and protrudes lips; compresses lips against teeth, and shapes lips during speech, (4) Buccinator - Presses cheeks against teeth and lips; draws corner of mouth laterally, and assists in mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks), and (5) Platysma Muscles - Draws outer part of lower lip inferiorly and posteriorly; depresses the mandible