We are going to test both light touch and pin prick on the face. And we need to test the three main areas of the face: the forehead, cheeks and over the chin – three components of trigeminal nerve, V1, V2, V3. Now, it is important to stay tight inside the face, don’t go way out. If you go too far out, you are within the cervical sensory dermatome, and you are not in the trigeminal dermatome. Now, to test the light touch, you may use a cotton swab or you can simply use your fingers, that’s fine, and have the patient close his eyes and ask if he feels, where he feels it, and then if it feels the same in both sides.
-“Close your eyes, sir. Okay, where am I touching you?”
-“Left forehead, right forehead.”
-“Same both sides?”
-“Yes.”
-“Right cheek, left cheek.”
-“Same both sides?”
-“Yes.”
-“Right chin, left chin.”
-“Same both sides?”
-“Yes.”
Now, we’ll use a pin. Now, it is best to use a safety pin. Don’t use a needle, because that will break the skin. But never reuse a pin on another patient. Very important for infection control purposes and there is no need to go hard, it is a very simple tap.
-“Now, I’m just going to poke you very gently. Close your eyes and tell me if you feel sharp or dull.”
-“Sharp, sharp.”
-“Same both sides?”
-“Yes.”
-“Sharp, sharp.”
-“Same both sides?”
-“Yes.”
-“Dull, sharp, sharp.”
-“Same both sides?”
-“Yes.”
Now, I simply use one dull stimulus to make sure he was paying attention. Sometimes the patients will say the same thing over and over, sharp, sharp, sharp, and not pay attention to what you are saying. That is the only reason why you need a negative stimulus. Notice, however, that when I did the negative stimulus, I went back and rechecked the positive stimulus in the same side, because what I really care about is can he feel the sharp stimulus in all the areas. If I skip over an area and don’t put sharp there, I won’t know if he can feel it. So, you don’t need to constantly be doing dull, sharp, dull, sharp – and occasional dull just to make sure that the patient is awake.