Introduction:

Cranial nerves are nerves that originate in the brain. Humans have 12 pairs of cranial nerves:
1). olfactory nerve
2). optic nerve
3). oculomotor nerve
4). trochlear nerve
5). trigeminal nerve
6). abducens nerve
7). facial nerve
8). vestibulocochlear nerve
9). glossopharyngeal nerve
10). vagus nerve
11). spinal accessory nerve
12). hypoglossal nerve

The functions of these nerves include carrying sensory information to the brain, controlling muscles, and regulating glands and internal organs. The first picture above depicts each cranial nerve's point of departure from the brain.

This particular Instructable focuses on cranial nerve 5, the trigeminal nerve. This nerve originates in the pons, a part of the brainstem, and has both sensory and motor functions. The trigeminal nerve controls muscles of mastication (biting and chewing) and carries sensory information about touch and pain from the face. The second picture above shows the three areas of the face that the trigeminal nerve innervates. This Instructable will demonstrate 3 useful exercises for checking a patient's trigeminal nerve function. By testing the sense of touch and the muscle contractions of the face, these exercises will demonstrate the trigeminal nerve's ability to carry sensory information from the face to the brain, and its ability to control the temporalis, masseter, and pterygoid muscles that manipulate the jaw.

Requirements:
1). basic understanding of anatomy
2). patient who is comfortable with his/her face being touched
3). Q-tip
4). scissors (for cutting the Q-tip in half)

Time: 10 minutes

Safety Concerns: The one performing the examination should be careful not to unnecessarily poke the patient with the Q-tip.

Images:
Lynch, Patrick J. "Brain human normal inferior view with labels en." Illustration. Wikipedia.com 04 May 2011. 03 April 2014. http://en.wikipedia.org/wiki/Cranial_nerves.
"Facial areas innervated by the trigeminal nerve." Illustration. Spinesurgery-wecareindia.com. 03 April 2014. http://www.spinesurgery-wecareindia.com/condition/trigeminal_neuralgia.html.

Step 1: Preparation

1). Get a Q-tip and cut it in half. It does not matter how long the halves are. Discard one of the halves. The cut Q-tip should look like the small Q-tip in the picture above. It should have a soft end and a blunt end.

2). Have the patient sit so that, as you stand, your patient's face is approximately at your eye level. You will be standing during the physical examination.

3). Again, as listed in the requirements, make sure your patient is comfortable with his/her face being touched. If not, this examination should not be performed on him/her.

Step 2: Testing Sensation

1). Say to the patient, "I'm going to test your facial sensation using a Q-tip that has been cut in half."

2). Gently rub the blunt end of the Q-tip on the back of the patient's hand and tell him/her that this is the sharp side.

3). Gently rub the cotton end of the Q-tip on the patient's hand and tell him/her that this is the soft side.

Be careful with the Q-tip. Avoid unnecessary poking of the patient's face, especially the eyes.

4). Say, "With your eyes closed I'm going to touch your face with either side of the Q-tip, and I want you to tell me if you feel the sharp side or the soft side."

5). (See the first picture above) Gently rub either side of the Q-tip on one of the patient's temples while asking, "Is this the sharp or soft side?" Make sure the patient answers correctly. If the patient does not answer correctly, continue with this entire exercise, and see the final comment.

6). Gently rub either side of the Q-tip on the patient's other temple while asking, "Sharp or soft?" Make sure the patient answers correctly. Again, if the patient does not answer correctly, continue until the end of this exercise.

7). Repeat with the patient's left and right cheeks, and then with both sides of the patient's chin (see the second and third pictures). You may use the sharp and soft ends of the Q-tip in any order, as long as you make sure the patient answers correctly.

If your patient was unable to identify the sharp or soft side of the Q-tip at any point throughout this exercise, make a mental note of it, but proceed with the entire examination, and the issue will be addressed in Step 5.

Step 3: Testing the Temporalis and Masseter Muscles

1). Say, "I'm now going to test your jaw."

2). Place one hand on each temple of the patient's head (see the first picture above).

3). Ask the patient to clench his/her jaw. Feel for a muscle contraction. This is the temporalis muscle that helps control the jaw. If you cannot feel a muscle contraction, continue with this exercise, and see the last comment.

4). Ask the patient to release his/her clenched jaw.

5). Place your hands close to the ear on each of the patient's cheeks (see the second picture).

6). Ask the patient to clench his/her jaw. Feel for a muscle contraction. This is the masseter muscle, which also helps control the jaw. Again, if there is no muscle contraction, proceed with the exercise.

7). Ask the patient to release his/her clenched jaw.

8). Remove your hands.

If you did not feel a muscle contraction at any point throughout this exercise, continue with the examination, and the issue will be addressed in Step 5.

Step 4: Testing the Pterygoid Muscles

1). Say, "Please open your jaw and keep it open."

2). Place one hand under the patient's chin and the other hand on top of the patient's head (see first picture above).

3). Say, "Don't let me close your jaw."

4). With a small amount of force, gently and briefly push the patient's chin up as if to close his/her mouth. You should not be able to close the patient's mouth because the pterygoid muscles should be strong enough to keep the jaw open. If you are able to close the patient's mouth with a small amount of force, continue with the exercise, and the issue will be addressed soon.

5). Remove your hands.

6). With the patient's mouth still open, ask, "Please move your jaw from side to side." Observe that the patient's jaw moves approximately the same distance to each side (see second picture above). If your patient's jaw does not move the same distance to each side, see the comment below.

If your patient performed as expected on all of the exercises (he/she correctly identified the sharp and soft ends of the Q-tip, exhibited muscle contractions, opposed you pushing on his/her chin, and moved his/her jaw the same distance to either side), then you are done with the examination and may skip to the conclusion of Step 5. If your patient did not perform as expected on all of the tests, proceed to the beginning of Step 5.

Step 5: What to Do When a Patient Displays Improper Nerve Function

Your patient may have displayed improper nerve function if he/she...

a). did not correctly identify the sharp or soft end of the Q-tip

b). did not exhibit muscle contractions

c). was not able to oppose you pushing on his/her chin

d). did not move his/her jaw the same distance to either side

There is no need to worry if your patient did not perform as expected on any of the three exercises.

1). Go back to the particular exercise where the patient performed incorrectly, and repeat the exercise twice.

2). If the patient is still not performing as expected and has no known neurological disorder (any disorder of the nervous system), ask the patient to see his/her physician about the issue. Again, there is no need to be concerned at this point. If you or your patient have any questions about a loss of sensation in the face or about problems with the jaw, please visit the website links below.

Conclusion:

Now you know how to test if someone’s trigeminal nerve is working! This nerve has an important role in facial sensation and in jaw motion, so it is crucial to have a functioning trigeminal nerve.

Thank you for reading this instructable. I hope it was fun and educational, and if you would like to learn more about the trigeminal nerve and its functions, please visit the following websites:

*Information on the trigeminal nerve:

http://www.dartmouth.edu/~dons/part_1/chapter_5.ht...

http://en.wikipedia.org/wiki/Trigeminal_nerve

*Information on numbness in the face:

http://www.nlm.nih.gov/medlineplus/ency/article/00...

http://www.newhealthguide.org/Numbness-In-Face.htm...

http://www.webmd.com/a-to-z-guides/facial-problems-noninjury-topic-overview

*Information on problems with the jaw:

http://www.patient.co.uk/health/temporomandibular-...

http://www.webmd.com/oral-health/temporomandibular-disorders