Affected muscles:
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Frontalis: Raises the eyebrows and wrinkles the forehead.
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Orbicularis oculi: Closes the eyelids.
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Zygomaticus major: Elevates the corner of the mouth, allowing for smiling.
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Orbicularis oris: Closes and puckers the lips.
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Buccinator: Helps in compressing the cheeks against the teeth, aiding in chewing.
Mechanism of Muscle Weakness:
The facial nerve runs through a tiny bony canal in the skull known as the facial canal. In Bell's palsy, inflammation, presumably caused by a viral infection, compresses the facial nerve within this canal, resulting in decreased nerve transmission. This results in muscle weakness or paralysis on the affected side of the face.
Other Symptoms of Facial Muscle Weakness:
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Inability to close the eye on the affected side, leading to eye dryness or irritation.
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Difficulty eating or drinking due to impaired lip control.
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Loss of taste on the anterior two-thirds of the tongue (if the chorda tympani branch of the facial nerve is involved).
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Hyperacusis (increased sensitivity to sound) due to paralysis of the stapedius muscle in the middle ear.
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Drooling due to difficulty controlling the lips.