5 muscles that could be affected:
- Orbicularis Oculi (closes eyes)
- Orbicularis Oris (closes and protrudes lips, compresses lips against teeth, and shapes lips during speech)
- Buccinator (presses cheeks against teeth and lips, draws corner of mouth laterally, assists in mastication by keeping food between teeth)
- Frontalis (raises eyebrows and wrinkles, protracts scalp)
- Platysma (draws outer part of lower lip inferiorly and posteriorly, depresses mandible)
Mechanism:
- Bell's Palsy is due to the damage of the facial (VII) nerve. The possible causes include: infection of ear, surgery of ear that caused damages to the facial nerve, and infection by herpes simplex virus.
Other symptoms include:
- speech difficulty
- drooling
- aching around the jaw and ear area
- weak eyelid closure
- numbing of the mouth or cheek
Reference:
Tortora, G. J., & Derrickson, B.H. (2011). Principles of Anatomy and Physiology 14th Edition. Wiley.