Bell’s Palsy- unilateral paralysis of the muscles of facial expression because facial (VIII) nerve got damaged.
Possible causes:
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ear infection,
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ear surgery that damages the facial nerve
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infection by the herpes simplex virus
Muscles Infected (action)
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Frontalis- moves scalp anteriorly, raises eyebrows, and wrinkles skin of forehead horizontally
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Orbicularis Oculi-closes eye
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Orbicularis Oris- Closes and protrudes lips, compresses lips against teeth; and shapes lips during speech.
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Buccinator- Presses cheeks against teeth and lips, as in whistling, blowing,
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and sucking; draws the corner of mouth laterally; and assists in mastication (chewing) by keeping food between the teeth (and not between teeth and cheeks).
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Platysma- draws outer part of lower lip inferiorly and posteriorly; depresses mandible
Other symptoms:
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Drooling.
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Pain around the jaw or in or behind your ear on the affected side.
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speech difficulty
Reference:
Principles of Anatomy & Physiology 14th Edition by Derrickson, B. and Tortora, G.