Muscles affected:
Frontalis - lift eyebrows, wrinkle forehead
Orbicularis oculi - closes the eyelids and assists in pumping tears
Orbicularis oris - control the shape and movements of the lips
Buccinator - maintains the tightness of the cheeks and presses them against the teeth during chewing
Platysma - lowers the corners of the mouth and lower lip
Mechanism of muscle weakness
Bell's palsy is an inflammatory process of the facial nerve leading to its compression along this narrow segment of the fallopian canal. This inflammation initially causes a temporary loss of sensory or motor function but can lead to permanent nerve degeneration later. (Loukas et al., 2014)
Loukas, Marios. “The Neurologist’s Dilemma: A Comprehensive Clinical Review of Bell’s Palsy, with Emphasis on Current Management Trends.” Medical Science Monitor, vol. 20, 2014, pp. 83–90, www.ncbi.nlm.nih.gov/pmc/articles/PMC3907546/, 10.12659/msm.889876.
Other symptoms of Bell’s Palsy
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Inability to wrinkle the forehead
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Inability to close eye
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Inability to pucker lips
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Drooling
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Difficulty in swallowing