CN IV Trochlear

Question 1

Where is the nucleus for the CN IV Trochlear located?

Answer 1

In dorsal medial caudal midbrain tegmentum (at level of inferior colliculus)

Question 2

Where does the CN IV Trochlear exit?

Answer 2

Crosses when it exits dorsally and descends to extreme caudal midbrain before crossing in order to exit inferior to the inferior colliculus

Question 3

Type of neurons are the CN IV Trochlear?

Answer 3

Voluntary motor

Question 4

One extraocular muscle?

Answer 4

Superior oblique

Question 5

When the eyelid is adducted, contraction of this muscle (Superior oblique) will depress the eye (test position is to have the patient look)

Answer 5

In and down

Question 6

Only cranial nerve that exits on the?

Answer 6

Dorsal side of the brainstem

Question 7

Where does the CN IV Trochlear exit at junction of?

Answer 7

Midbrain and pons, then wraps around outside the brainstem to join the others on the anterior side

*Posterior aspect injury will affect this nerve

Question 8

The CN IV Trochlear is the only cranial nerve where all fibers cross just before?

Answer 8

Exiting!

Question 9

Left nucleus controls?

Answer 9

Right eye but left nerve controls left eye

Question 10

Right nucleus controls?

Answer 10

Left eye but right nerve controls right eye.

Question 11

Injury to nerve or nucleus?

Answer 11

Diplopia

• Affected eye positioned slightly up
• Trouble looking down when adducted (trouble descending stairs and reading)