Stroke vs Bell`s Palsy

Diagnosis

How the doctors knew Julia did not have a stroke...

When Julia awoke with a crooked smile she thought she had suffered a stroke because she could not move the right side of her face. Her eye would not close completely and she could not raise the corner of her mouth. Her grandfather had recently suffered a stroke and Julia worried that she also had a stroke because, in the mirror, her face looked like her grandfather's. However, the doctors could see a subtle difference in the weakness caused by a stroke and weakness caused by Bell's palsy also known as facial nerve paralysis. A stroke is a condition that arises when cerebral neurons are injured by the sudden blockage of blood supply to that part of the brain. These neurons initiate movements of the face by sending signals to neurons in the brainstem. From the brainstem nerve fibers spread out to cover the face (see Figure 1).

Why the face looks different following a stroke compared to following a primary facial nerve injury (Bell's palsy)

Figure 1. The facial nerve and muscles of the face*

In general, cerebral neurons from the left side of the brain send their signals to brainstem neurons whose nerves innervate muscles on the right side of the face and right sided cerebral neurons go to brainstem neurons that innervate muscles on the left side. However, the facial nerve is somewhat unusual in that the fibers that spread to the upper face (muscles around the eye and the forehead) come from cerebral neurons on BOTH the right and left side of the brain. This results in a difference between how facial paralysis looks if there is injury to the brain (from a stroke) or injury to the facial nerve itself (Bell's palsy). Look at the faces in Figure 2. Why is the woman's face that of someone who had a stroke and the man's face that of someone with Bell's palsy?

Figure 2.*

Answer: If you can raise both eyebrows, the facial nerve is intact. Therefore, the woman has had a stroke involving the left side of the brain producing paralysis of the right lower face and the man has a right Bell's palsy.

* Topical Diagnosis in Neurology, by Peter Duus, Thieme Medical Publishers, Inc.   New York 1989

Photographs and diagrams reprinted with permission

Source:http://www.fbr.org/swksweb/immunolymeface.html