Muscles Affected by Bell's Palsy:
- Depressor anguli oris
Action: Draws angle of mouth laterally and inferiorly (i.e. opening mouth) - Orbicularis oculi
Action: Closes eye - Orbicularis oris
Action: Closes and protrudes lips (i.e. kissing); compresses lips against teeth; and shapes lips during speech - Buccinator
Action: Presses cheeks against teeth and lips (i.e. whistling, blowing, and sucking); draws corner of mouth laterally; and assists in mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks) - Platysma
Action: Draws outer part of lower lip inferiorly and posteriorly (i.e. pouting); depresses mandible
Mechanism of Muscle Weakness:
Bell's Palsy is a disorder of the seventh cranial nerve, which controls the movement of the muscles in the face. The exact cause of this condition is unknown, but experts believe that the condition is caused due to swelling and irritation of the nerve, affecting the muscles on one side of the face. Damage to this nerve causes weakness or paralysis of the muscles mentioned above.
Other Symptoms:
- Loss of taste
- Changes in the amount of tears or saliva
- Drooling
- Difficulty eating and drinking
- Drooping of one side of the mouth