Have you ever wondered "Is my doctor wacky?" when you go into a physical and the doctro starts telling you to puff out your cheeks, stick out your tounge, shrug your shoulders, blink your eyes etc... It doesn't make any sense. I am going to tell you that each one of those movements really does have a lot of information and value and here's why?
When your doctor asks you to smell, or asks about your "smelling ability" he is actually testing your Olfactory Nerve. If you were to have a decrease in smell or loss of smell, this could indicate an abnormality in this nerve.
When your Doctor looks inside your eyes with that "little light instrument" called a fundoscope he is actually looking at the Optic nerve which leaves the back of your eye. When he tests your visual acuity (i.e. read the eye chart E F P D....) he is also evaluating the optic nerve. If you were to loose vision in a certain area of your eye this can indicate which side of the optic nerve there is a problem. For example if you loose your vision in only your right eye, he would deduce that a problem might exist in the Right optic nerve and NOT the left optic nerve. It gets a lot more complicated from here, but it's fun to learn.
When your doctor makes you follow his finger while he draws an "H" in the air and eventually puts his finger between your eyes so you are then cross-eyed, he is testing THREE nerves. Each one of the these nerves innervates different muscles in your eyes and therefore are responsible for certain movements. For example if you look to the right, one of your eyes might be able to go much further to the right than the other, this can indicate either weakness of that specific muscle or a problem with the nerve innervating that muscle. I think it's funny because many of us have a hard time going "cross-eyed" and this indicated weak eye muscles (usually not a nerve problem). Soooo in yoga there is something called "eye-exercises" in order to keep these muscles strong. Check it out!
When your doctor asks you to open your mouth, and touches your face with cotton balls, this is not for pure enjoyment, it is actually to locate different sensation patterns on your face. If you were to have less or no feeling on your left forehead compared to your right forehead, the doctor could deduce that there is an abnormality in a branch of the Trigeminal nerve (which innervates your entire face via 6 branches). The facial nerve also innervates the muscles that help you open your mouth, if you can't open your mouth..... nerve problem??? maybe
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When your doctor asks you to puff out your cheeks, raise your eyebrows, frown, smile... he is actually testing different branches of the Facial nerve. If you notice sometimes people can smile higher on one side than the other, this could indicate less innervation on that side. Each facial action test each area of the facial nerve, so look to see if things are the same on both sides of your face. If you had a problem with certain branches you might not be able to lift your right eyebrow, but you can your left.
I think this one is self-explanatory - your vestibulocochlear nerve tests your hearing, but when and if your Dr. tickles your ear canal with cotton, he is also testing a reflex to make sure this nerve has sensation and not only "hearing" function.
Have you ever wondered why the Dr asks you to say AHHHHHH, it is not to see if you can speak, he is actually looking at the funky peach drop from the top of your mouth called the uvula. He is looking to see if it RISES (look in the mirror and see it rise) because if it doesn't or only half of it does, this indicates a nerve problem with the glossopharyngeal, vagus nerve!
A simple shrug of your shoulders tells the doctor if your Spinal Accessory nerve is intact...
Last but not least, when the doctor tells you to stick out your tongue he is actually testing the strength of your hypoglossal nerve. Sometimes people might be able to stick out their tongue but it might go to one side, this indicates that the other side is not working or weak etc...
So I hope this was fun for you so next time your Wacky doctor plays "head, shoulders, knees and toes" you can be happy to do it!
smell, watch, cross-eyes, open your mouth, tickle-tickle your face, raise your eyebrows, puff out your cheeks, smile, frown, tickle-tickle your ear, AHHHHHHH, shoulder shrug, stick out your tongue... YOU'VE JUST TESTED ALL TEN OF THE CRANIAL NERVES!!! good job!