5 Muscles affected by Bell’s palsy & Actions
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Frontalis
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Action: Raises eyebrows and wrinkles forehead
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Orbicularis oculi
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Action: Closes eyelids
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Orbicularis oris
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Action: Closes and compresses the lips
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Buccinator
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Action: Presses cheeks against teeth and lips, draws angle of mouth laterally and superiorly
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Platysma
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Action: Draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible
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Mechanism of the patient’s muscle weakness
Bell’s Palsy is a facial paralysis which is caused by dysfunction of cranial nerve VII. It results in inability or reduced ability to move the muscles on the affected side of the face. The facial nerve being damaged by inflammation caused it to become enlarged. Ischemia develops when a nerve swells within its bone canal, obstructing the flow of blood to the nerve. Although this inflammation initially results in a brief loss of sensory or motor function, it has the potential to subsequently induce permanent nerve damage.
Other symptoms the patient may exhibit as a result of facial muscle weakness
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Trouble in retaining saliva on the affected side of the face
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Difficulty closing an eyelid
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Ability to wrinkle the forehead is limited
References:
Mayo Clinic. (2022). Bell’s palsy. https://www.mayoclinic.org/diseases-conditions/bells-palsy/symptoms-causes/syc-20370028#:~:text=Facial%20weakness%20or%20paralysis%20may,affected%20side%20of%20your%20face
Rubin, M. (2022). Facial Nerve Palsy. https://www.merckmanuals.com/en-ca/professional/neurologic-disorders/neuro-ophthalmologic-and-cranial-nerve-disorders/facial-nerve-palsy
Sheffield, S. (2022). Frontalis Muscle - Attachments, Actions & Innervation. https://www.getbodysmart.com/facial-expression-muscles/frontalis-muscle/
Taylor, D. (2021). Bell Palsy. https://emedicine.medscape.com/article/1146903-overview#:~:text=The%20facial%20nerve%20passes%20through,%2C%20buccinator%2C%20and%20platysma%20muscles.
Tortora, G., & Derrickson, B. (2017). Principles of Anatomy & Physiology (15th ed.). John Wiley & Sons, Inc.
Zandian, A., Osiro, S., Hudson, R., Ali, I., Matusz, P., Tubbs, S., & Loukas, M. (2014). The neurologist’s dilemma: A comprehensive clinical review of Bell’s palsy, with emphasis on current management trends. http://doi.org/10.12659/MSM.889876