Five of the muscles affected by Bell’s palsy include the frontalis, orbicularis oculi, orbicularis oris, buccinator, and platysma muscles. This condition is the most common cause of unilateral facial paralysis and one of the most common neurologic disorders of cranial nerves. The most probable mechanism of this is an inflammatory process of the facial nerve, which results in its compression along this narrow segment of the fallopian canal. The inflammation initially causes temporary sensory or motor function loss, but might lead to permanent nerve damage in the long run. Other symptoms include acute onset of unilateral upper and lower facial paralysis, posterior auricular pain, ocular pain, blurred vision, epiphora, poor eyelid closure, and more.
Actions of the muscles:
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Frontalis: move eyebrows up, wrinkle forehead, move scalp
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Orbicularis oculi: close eyelids, compress lacrimal sac
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Orbicularis oris: close mouth, compress and protrude lips
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Buccinator: compress cheek against molar teeth
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Platysma: depress mandible and angle of mouth, tense skin of lower face and anterior neck