According to the National Institute of Neurological Disorders and Stroke (NINDS), "Bell's palsy is a neurological disorder that causes paralysis or weakness on one side of the face" (1). It occurs suddenly and can worsen within the first two days (2).
It is believed that it is caused due to the facial nerve (seventh cranial nerve) being damaged (2), but the exact cause is unknown (3). The facial nerve...contains the motor, sensory, and parasympathetic (secretomotor) nerve fibers, which provide (nerves) to many areas of the head and neck region" (4). Swelling and irritation that controls the muscles on one side of the face may also be a root cause for this impairment (3).
More to follow...
A "map" of the seventh cranial nerve and its branches.
Sources:
1. https://www.ninds.nih.gov/health-information/disorders/bells-palsy (Information accessed on: 25 October 2024)
2. https://www.hopkinsmedicine.org/health/conditions-and-diseases/bells-palsy#:~:text=Bell%20palsy%20is%20an%20unexplained,of%20the%20face%20or%20head. (Information accessed on: 25 October 2024)
3. https://www.mayoclinic.org/diseases-conditions/bells-palsy/symptoms-causes/syc-20370028 (Information accessed on: 25 October 2024)
4. https://www.ncbi.nlm.nih.gov/books/NBK554569/#:~:text=The%20facial%20nerve%20is%20the,The%20main%20motor%20nucleus (Information accessed on: 25 October 2024)