Cranial nerves V-VIII
In this lesson, we’ll cover cranial nerves V-VIII.
1) Watch the following videos about cranial nerves V through VIII:
2) Next, watch this video about a reflex involving cranial nerves V and VII:
3) Watch these videos to learn about disorders involving cranial nerves V and VII, respectively:
4) Finally, answer these questions to test your understanding:
1. Marcus is hit in the forehead with a baseball and immediately feels sharp pain in that area. Which division of the trigeminal nerve carries this sensory information?
- A. ophthalmic division (V1)
- B. maxillary division (V2)
- C. mandibular division (V3)
- D. none of the above; it would be carried by the facial nerve
Show Answer
Correct answer: A
The trigeminal nerve is the main sensory nerve of the head. It has three divisions, the ophthalmic, maxillary, and mandibular divisions, which supply three different regions of the head and face. The forehead is supplied by the ophthalmic division of the trigeminal nerve.
2. This cranial nerve innervates the lateral rectus muscle to move the eye laterally, toward the side of the head:
- A. optic nerve (CN II)
- B. oculomotor nerve (CN III)
- C. trochlear nerve (CN IV)
- D. abducens nerve (CN VI)
Show Answer
Correct answer: D
The abducens nerve innervates the lateral rectus muscle to move the eye laterally.
3. Bell's palsy is characterized by facial weakness or paralysis and results from dysfunction of which cranial nerve?
- A. CN III
- B. CN VII
- C. CN X
- D. CN XI
Show Answer
Correct answer: B
Bell’s palsy is a disorder that results from the dysfunction of cranial nerve VII, the facial nerve. It involves weakness or paralysis, typically on one side of the face. The cause of Bell's palsy is not clear, and Bell’s palsy is only diagnosed when there is not another identifiable cause of the facial paralysis (e.g., Lyme disease, trauma).
4. A doctor lightly touches a patient's right cornea with a wisp of cotton. Her right eye blinks, but her left eye does not. What does this suggest?
- A. a deficit with the right trigeminal nerve
- B. a deficit with the right facial nerve
- C. a deficit with the left trigeminal nerve
- D. a deficit with the left facial nerve
Show Answer
Correct answer: D
The corneal reflex is used clinically to assess the trigeminal nerve (sensory/afferent limb) and the facial nerve (motor/efferent limb). Touching the right cornea should produce blinking in both eyes. Because the right eye blinks, the right trigeminal nerve and right facial nerve are intact. The absence of blinking in the left eye indicates a deficit in the left facial nerve.
5. What is typically the main symptom of trigeminal neuralgia?
- A. Progressive facial muscle weakness
- B. Persistent numbness in the cheek and jaw
- C. Sudden, severe, stabbing facial pain
- D. Difficulty swallowing and speaking
Show Answer
Correct answer: C
Trigeminal neuralgia, also known as tic douloureux, is a disorder of cranial nerve V, the trigeminal nerve. The trigeminal nerve is the main sensory nerve for the face; it also controls motor functions of the jaw like biting and chewing. Trigeminal neuralgia is a pain disorder that causes sudden intense pain, typically on one side of the face.
