Your 60-year-old patient, Mr. Guster, has Bell's palsy, which causes dysfunction of those portions of the facial nerve that control muscles of facial expression. He is surprised when you tell him to tape the eyelids of his right eye closed at night to prevent dryness. Why might Bell's palsy cause dryness of the eye on the affected side?

Verified step by step guidance

1. Understand that Bell's palsy affects the facial nerve, specifically cranial nerve VII, which is responsible for controlling the muscles of facial expression.
2. Recognize that the facial nerve also innervates the lacrimal glands, which are responsible for tear production.
3. Consider that dysfunction of the facial nerve can lead to a decrease in tear production, resulting in dryness of the eye.
4. Acknowledge that Bell's palsy can cause weakness or paralysis of the orbicularis oculi muscle, which is responsible for closing the eyelids.
5. Realize that if the eyelids cannot close properly, the eye is exposed to the environment, leading to increased evaporation of tears and further dryness.

Key Concepts

Facial Nerve Function

The facial nerve (cranial nerve VII) is responsible for controlling the muscles of facial expression, as well as providing sensory functions such as taste from the anterior two-thirds of the tongue. In Bell's palsy, inflammation or damage to this nerve leads to weakness or paralysis of the facial muscles, which can affect the ability to close the eyelids properly, resulting in exposure of the eye.

Corneal Protection and Tear Production

The eyelids play a crucial role in protecting the cornea and maintaining moisture on the surface of the eye through blinking, which spreads tears. When the eyelids cannot close fully due to facial nerve dysfunction, the eye is left exposed, leading to increased evaporation of tears and potential dryness, which can cause discomfort and increase the risk of corneal damage.

Management of Eye Dryness

To manage eye dryness resulting from Bell's palsy, protective measures such as taping the eyelids closed at night can be employed. This helps to prevent exposure and maintain moisture in the eye, reducing the risk of complications like corneal abrasions or infections, and is an important aspect of patient care in individuals with facial nerve impairment.