Muscles Affected:
Frontalis - When this muscle is affected, the patient can’t raise their eyebrows on the affected side, leading to a smooth, flat forehead.
Orbicularis oculi - With Bell's palsy, the patient struggles to fully close the eye on the affected side, which can cause the eye to remain partially open, leading to dryness and irritation.
Zygomaticus major and minor - These muscles are responsible for smiling by lifting the corners of the mouth. When they don’t work properly, the patient can’t smile fully on the affected side, which causes facial drooping and an uneven smile.
Orbicularis oris - This muscle controls the lips. When weakened, the patient has trouble closing their mouth tightly, leading to drooling or difficulty drinking without spilling.
Buccinator - This muscle helps hold the food in the mouth while chewing and also helps with blowing. In Bell’s palsy, food may fall out of the mouth, and patients might drool from the weak side.
Muscle Mechanism:
The Cranial Nerve VII controls these muscles. In Bell’s palsy, there is an inflammation or compression of this nerve, which disrupts its ability to send signals to the muscles on one side of the face. This is why the patient can’t move the left side of their face.
The exact reason isn’t always clear, but it’s often linked to viral infections like the herpes virus (the one responsible for cold sores). The inflammation can press on the nerve as it travels through a narrow bony canal in the skull, leading to muscle weakness or paralysis.
Other Symptoms:
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Because they can’t fully close the left eye, it might dry out or become irritated. If left untreated, this could damage the eye.
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Since the muscles around the mouth are weak, it’s common to see drooling from the affected side.
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The left side of their mouth is drooping, so they may struggle with certain words, especially ones that require lip movement (like "P" or "B").
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Food or liquids may spill from the affected side, making eating and drinking tricky.
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The facial nerve also affects taste, so they might notice food doesn’t taste the same on the front two-thirds of their tongue.
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Sometimes patients become more sensitive to loud sounds because the stapedius muscle in the ear (also controlled by the facial nerve) stops working.