Muscles affected and its actions:
1. orbicularis oculi: closes eye
2. orbicularis oris: closes and protrudes lips, as in kissing; compresses lips against teeth; and shapes lips during speech.
3. 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).
4. platysma: draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible.
5. frontalis: draws scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally as in look of surprise.
Mechanism:
Inflammatory process of cranial nerve VII (facial nerve) that results to its compression which leads to temporary loss of sensory and/or motor functions.
Symptoms:
- facial droop
- drooling
- loss of taste
- change in the production amount of tears and saliva
- increased sensitivity to sound (on affected side of the face)
Reference:
https://doi.org/10.12659/MSM.889876
https://www.mayoclinic.org/diseases-conditions/bells-palsy/symptoms-causes/syc-20370028
https://emedicine.medscape.com/article/1146903-overview