Chapter 5: Facial sensations & movements

Questions

Define the following terms:

hyperacusis, ageusia.
Hyperacusis is the excessive perception of sound.
Ageusia is the loss of taste perception.

5-1. Which division of the trigeminal nerve has motor fibers?

Answer 5-1. Only the mandibular division of the trigeminal nerve has motor fibers (to the muscles of mastication).

5-2. What are some good ways to distinguish hysterical sensory loss on the face?

Answer 5-2. The trigeminal nerve does not follow artificial lines on the head (hairline, jawline), and there is no lesion that will abolish the ability of the patient to detect a vibrating tuning fork placed on a bony prominence of the skull. The corneal reflex may be useful as well.

5-3. Where is the trigeminal ganglion located?

Answer 5-3. The trigeminal ganglion is lateral to the sella turcica/pituitary and in wall of cavernous sinus.

5-4. Where does the trigeminal nerve root enter the brain?

Answer 5-4. CN V enters the pons.

5-5. Which modalities would test the integrity of the spinal tract of the trigeminal nerve?

Answer 5-5. Pain and temperature sense.

5-6. Where do pain and temperature nerve fibers in the trigeminal nerve run after entering the pons?

Answer 5-6. Pain and temperature fibers run caudally through the lateral brain stem to reach the spinal nucleus of V in the medulla and upper spinal cord; lateral brain stem lesions can block ipsilateral pain from face.

5-7. What is the pathway of the corneal reflex?

Answer 5-7. The sensory limb of the corneal reflex is the ophthalmic division of the trigeminal nerve and the motor limb is the facial nerve. The response is consensual.

5-8. What are the symptoms of Bell's palsy?

Answer 5-8. Bell's palsy damages the facial nerve in the facial canal and weakens all muscles of facial expression on the side of lesion. Depending on where the damage occurs, there may be hyperacusis or loss of taste on that side of the tongue.

5-9. How can you distinguish weakness of the face that is due to damage to the brain (such as with a stroke) from weakness due to damage of the facial nerve?

Answer 5-9. Damage to corticobulbar fibers (from cortex to the pons) will produce supranuclear weakness of the lower face (sparing of forehead) on the contralateral side, while damage to the nerve should produce weakness of all muscles of facial expression on that side.

5-10. Describe the reflex arc of the jaw-jerk reflex.

Answer 5-10. Jaw jerk reflex - afferent is trigeminal, efferent is trigeminal. It is a muscle stretch reflex with the reflex center in the pons (sometimes called the pontine reflex).