Let us look at the facial muscles.
Our face has a lot of different muscles for different things, but only some of them are controlled by the facial nerve CN-VII (The seventh Cranial Nerve). These are known as ďThe muscles of facial expressionĒ and, as you have found out, control the movements of our face that create our expressions.
Unlike other muscles these go directly into the skin and therefore a contraction of these muscles makes your skin move and thus creates the required expression.
With over 7000 nerve endings attached to these muscles, when instructed by your brain to move, they can do that either individually or together to create in excess of 2000 different facial expressions.
When, as in Bellís Palsy, these instructions are temporarily prevented from getting through, the result is that the muscles will not move until these instructions can get through again. Thus, we see this as a paralysis or weakness of our facial expression.
Fortunately, unlike some other muscles, the facial muscles do not begin to atrophy (the wasting or loss of muscle through lack of use) for a long time even though they are not in fact being used. Amazingly, it is now believed that this could in fact be a period of years before this could happen.
Not all the facial muscles are affected by Bellís Palsy. It is only the 7th Cranial Nerve that is affected and not the others, of which there are 12 in all.
Therefore, your eye moves perfectly, although your eyelid, eyebrow, and skin under your eye will not. Similarly your tongue will still work, you will still be able to chew and to swallow, although sometimes your taste may be affected.
We are only concentrating on this 7th Cranial Nerve as that is the only one affected. So what exactly is it, where does it go and what does it do?
THE 7TH CRANIAL NERVE (CN-VII, the facial nerve)
The easiest way to describe what it would look like is to imagine a telephone cable coming into your house through a hole in the wall. As it comes inside of your house the one thicker cable opens up into the many cables that you see are inside it to be routed and connected to the correct terminals that require stimulation.
Stimulation comes from your brain and thoughts. You decide to smile and the electrical impulses that are required for a smile are transmitted down the thick cable, through the wall into your house and then follow the specific smaller cable that are correctly connected to those muscles that create your smile. This all happens in milliseconds.
There are more than 7000 of these smaller cables that come out of the 7th cranial nerve and they all need that electrical impulse from your brain to be able to contract and work to form your required expression.
The facial nerve controls the muscles of our neck, forehead and our facial expressions but also stimulates the secretions of our tear glands and our salivary glands as well as transmitting the taste sensation of the front 2/3 of our tongue and our perception of sound from the stirrup bone (the stapes) in our ear.
So, if we use our analogy of a telephone cable and insert the correct terms of its complex route from the thought in our brain to our resulting facial expression, we can then look at what has gone temporarily wrong and what needs to happen for this temporary condition to rectify itself.
The 7th Cranial Nerve (CN-VII) originates in an area of the brain known as the Pons or brain stem (this is at the base of our skull)
After leaving the brain stem (pons) the nerve enters the temporal bone (bone of our ear) through the internal auditory canal (this is why our sense of hearing and balance can sometimes be affected)
Along its inch-and-a-half course through a small canal within the temporal bone (the fallopian canal) the facial nerve winds around the three middle ear bones, the back of the eardrum, and then out through the Stylomastoid Foramen (the bony area behind our ear).
After it has left the Stylomastoid Foramen the nerve enters the Parotid gland (our saliva gland) and this is where it starts to divide into many branches, each one continuing to divide into over 7000 nerve endings that attach to and work (if supplied with an electrical impulse) our facial expressions.
So we can return to our telephone cable analogy and explain what has temporarily gone wrong and what needs to happen for the problem to be rectified.
Imagine that the fallopian canal (see above) is the hole in the wall of your house. This is large enough for the main cable containing all of the smaller cables to come through and therefore for the messages to travel along these cables.
Now, if that hole became smaller due to some outward pressures that started to constrict the large cable and therefore the smaller cables and therefore the messages that were travelling along them, the result would be that no messages would get through. This is exactly what has happened.
Bells Palsy is caused by inflammation within the fallopian canal or of the actual facial nerve within the fallopian canal. It is already very narrow and because it is a bony canal, any pressure that is caused has nowhere to go to be released and therefore can only continue to constrict what is contained therein, our facial nerve.
Bellís Palsy is the most common form of a sudden paralysis or weakness or the facial muscles. It is most probably due to our bodyís response to a virus (most probably the Herpes Simplex Virus HSV-I). The facial nerve, as it goes through the fallopian Canal, swells and therefore creates pressure upon itself and thus becomes temporarily damaged and constricted.
Because the nerve has not yet divided into its many smaller nerve endings (smaller cables) this constriction results in the blocking of all of the main nerve messages and therefore all of the nerve endingsí messages that create our facial expression.
No electrical impulses can get through until the inflammation reduces to allow them.
Therefore, if only part of the face is affected, for instance the lower half, but the forehead and eye areas all work then the diagnosis would not be Bellís Palsy, as the nerve in that instance must have been injured or affected after it had split into its 7000 divisions.
(If you have contracted Bellís Palsy following surgery or via an accident then your medical professional will know that this is the case, whereabouts the nerve has been affected and what the remedies are for your specific problem.)
In the book All Bells and No Whistle I have purposefully explained the most common diagnosis tools. However, it is far more normal for a quick diagnosis to be given at your first appointment with your doctor. So do not worry, if you have been diagnosed already with Bellís Palsy then that is what you have.
Robert Wilkinson is the author of All Bells and No Whistle - the self help guide for living with and recovering from Bell's Palsy He is currently writing his latest book on the subject of stress.
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