The Testing of the Glossopharyngeal nerve and the Motor function of the Vagus nerve

Question 1

In the OSPE, the examiner may ask you to recall how you might test the glossopharyngeal nerve. How would you do this and would you actually have to do it in the exam?

Answer 1

You would say “the actual test involves asking the patient to open their mouth, informing them that the test may be uncomfortable, and use a tongue depressor (a wooden lollipop stick) to gently touch the back of their throat to elicit the patient’s gag reflex”
- won’t have to actually do it in the OSPE

Question 2

What is the physiology behind this test?

Answer 2

The gag reflex physiology is simple

• the sensory limb is mediated by the glossopharyngeal nerve (CN IX) which innervates the oropharynx and the posterior 1/3rd of the tongue
• the motor limb is mediated by the vagus nerve (CN X)

Question 3

How would you test the motor function of the vagus nerve?

Answer 3

Ask the patient to open their mouth and say “ahh”

• Use a pen torch to look to the back of the patient’s mouth and observe the uvula
• The uvula should elevate and should not deviate from the midline

Question 4

What has happened if the uvula deviates to one side?

Answer 4

A lesion in the opposite side to the deviation’s vagus nerve has occurred, paralysing the muscles in that side of the face allowing the muscles on the opposite side of the face to pull the uvula up and towards them.