Testing The Facial Nerve
Voluntary facial movements, such as wrinkling the brow, showing teeth, frowning, closing the eyes tightly (inability to do so is called lagophthalmos), pursing the lips and puffing out the cheeks, all test the facial nerve. There should be no noticeable asymmetry.
In an UMN lesion, called central seven, only the lower part of the face on the contralateral side will be affected, due to the bilateral control to the upper facial muscles (frontalis and orbicularis oculi).
Lower motor neuron lesions can result in a CNVII palsy (Bell's palsy is the idiopathic form of facial nerve palsy), manifested as both upper and lower facial weakness on the same side of the lesion.
Taste can be tested on the anterior 2/3 of the tongue. This can be tested with a swab dipped in a flavoured solution, or with electronic stimulation (similar to putting your tongue on a battery).
Corneal reflex. The afferent arc is mediated by the General Sensory afferents of the Trigeminal Nerve. The efferent arc occurs via the Facial Nerve. The reflex involves consensual blinking of both eyes in response to stimulation of one eye. This is due to the Facial Nerve's innervation of the muscles of facial expression, namely Orbicularis oculi, responsible for blinking. Thus, the corneal reflex effectively tests the proper functioning of both Cranial Nerves V and VII.
Read more about this topic: Facial Nerve
Famous quotes containing the words testing the, testing, facial and/or nerve:
“Traditional scientific method has always been at the very best 20-20 hindsight. It’s good for seeing where you’ve been. It’s good for testing the truth of what you think you know, but it can’t tell you where you ought to go.”
—Robert M. Pirsig (b. 1928)
“Bourbon’s the only drink. You can take all that champagne stuff and pour it down the English Channel. Well, why wait 80 years before you can drink the stuff? Great vineyards, huge barrels aging forever, poor little old monks running around testing it, just so some woman in Tulsa, Oklahoma can say it tickles her nose.”
—John Michael Hayes (b.1919)
“You must call up every strength you own
And you can rip off the whole facial mask.”
—William Dewitt Snodgrass (b. 1926)
“Tom: All right, boys. C’mon. Why don’t you say I’m a yellow belly and a big mouth at that?
Shep: You yellow? Who thinks you’re yellow? Did you hear what he said? A guy who’s got the nerve to marry? That’s more than Flash Gordon ever did.”
—Billy Wilder (b. 1906)