Bell's palsy is a condition that causes sudden weakness in the muscles on one side of the face. The exact cause of Bell's palsy is unknown, but experts think it's caused by swelling and inflammation of the nerve that controls the muscles on one side of the face. The nerve that controls facial muscles passes through a narrow corridor of bone on its way to the face. In Bell's palsy, that nerve becomes inflamed and swollen, usually related to a viral infection. The weakness makes half of the face appear to droop, and smiles are one-sided, and the eye on the affected side resists closing. The following are the five muscles affected by Bell's palsy and their actions:
1. Orbicularis oculi - closes the eyelid
2. Orbicularis oris - closes the lips
3. Buccinator - compresses the cheek
4. Frontalis - raises the eyebrows
5. Zygomaticus major - raises the corner of the mouth
Other symptoms that the patient could exhibit as a result of facial muscle weakness include dry eye, dry mouth, headache, facial pain or abnormal sensations, excessive tearing in one eye, problems with taste, low tolerance for loud noises, pain around the jaw and behind the ear, and problems eating or drinking.
References
Bell’s Palsy. (2023). National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/bells-palsy
Tortora, G. J., & Derrickson, B. (2017). Principles of anatomy and physiology (15th ed.). Wiley Custom Learning Solutions. https://handoutset.com/wp-content/uploads/2022/05/Principles-of-anatomy-and-physiology-Wiley-2017-Derrickson-Bryan-H._-Tortora-Gerard-J..pdf