5 muscles affected and their action:
-
Frontalis - draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally as in a look of surprise
-
Orbicularis oculi - closes eye
-
Orbicularis oris - closes and protrudes lips, as in kissing; compresses lips against teeth; and shapes lips during speech
-
Buccinator - presses cheeks against teeth and lips, as in 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 muscles - draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible
Mechanism of his muscle weakness:
-
Bell palsy is the most common cause of unilateral facial paralysis and one of the most known neurologic disorders of the cranial nerves. This condition primarily arises from the dysfunction of cranial nerve VII, which connects the brain to the muscles that control facial expression (the nerve also is involved with taste and ear sensation). In rare cases, Bell's palsy can affect both sides of the face. The exact cause of Bell's palsy remains somewhat elusive and is still a subject of ongoing research. Several factors, including viral infections, inflammation, and autoimmune reactions, have been suggested as potential triggers, but no single cause has been definitively identified.
Other symptoms:
- drooling
- difficulty speaking, eating, or drinking
- facial or ear pain
- headache
- loss of taste
- tinnitus (ringing in the ear)
- hyperacusis (sensitivity to sounds)
References:
Cleveland Clinic Medical. (2023, August 14). Bell’s Palsy. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/5457-bells-palsy
Taylor, D. (2023, June 13). Bell Palsy. Practice Essentials, Background, Anatomy. https://emedicine.medscape.com/article/1146903-overview