Unit II: Cranial Nerves IV, VI

Question 0

Where is the trochlear nucleus?

Answer 0

Periaqueductal gray, just caudal to the oculomotor nuclei

Question 1

What muscle is supplied by cranial nerve IV?

Answer 1

Superior oblique

Question 2

What is unique about the pathway of the trochlear nuclei?

Answer 2

They decussate as they leave the CNS and head posteriorly to exit from the midbrain just inferior to the inferior colliculi

Question 3

From which area do the trochlear nuclei receive information?

Answer 3

Bdmn. Area 8, superior colliculus, medial longitudinal fasciculus

Question 4

After leaving the brainstem on the posterior side, where is cranial nerve IV carried in its pathway?

Answer 4

Cavernous sinus

Question 5

Cranial nerve IV communicates with what structure while in the cavernous sinus?

Answer 5

Cavernous plexus (postganglionic sympathetic fibers)

Question 6

Why is cranial nerve IV named trochlear nerve?

Answer 6

For the pulley-like mechanism located on the superomedial aspect of the orbit

Question 7

What passes through the trochlea located on the superomedial aspect of the orbit?

Answer 7

The superior oblique muscle (not the trochlear nerve)

Question 8

What muscle is supplied by cranial nerve VI?

Answer 8

Lateral rectus

Question 9

What is the location of the abducens nucleus (nucleus of origin)?

Answer 9

On the floor of the rhomboid fossa, on the inferior part of the pons

Question 10

What is the name of the nucleus of origin for cranial nerve IV?

Answer 10

Trochlear nucleus

Question 11

Cranial nerve VI exits the skull through which structure?

Answer 11

Superior orbital fissure

Question 12

What occurs with internal strabismus?

Answer 12

Affected eye deviates medially (eyes cross, converge)

Question 13

What occurs with external strabismus?

Answer 13

Affected eye deviates laterally (eyes are directed away from each other, diverging)

Question 14

What is the term for double vision?

Answer 14

Diplopia

Question 15

What is the term for the condition where the eyelid droops due to a weakness of the levator palpebrae superioris?

Answer 15

Ptosis

Question 16

What could be the cause of ptosis?

Answer 16

Oculomotor nerve lesions

Question 17

What is the issue when dealing with complaints of diplopia?

Answer 17

It is completely subjective

Question 18

What is seen with oculomotor paralysis (external opthalmoplegia)?

Answer 18

Ptosis, diplopia, diverging strabismus (external)

Question 19

What would we see with trochlear paralysis?

Answer 19

Slight converging strabismus, diplopia when looking down (difficulty descending stairs)

Question 20

Which is the most common visual cranial nerve paralysis?

Answer 20

Abducens paralysis

Question 21

What is seen with abducens paralysis?

Answer 21

Weak abduction, converging strabismus (internal), diplopia

Question 22

What is internuclear ophthalmoplegia?

Answer 22

Damage to the medial longitudinal fasciculus

Question 23

What is the result of internuclear ophthalmoplegia?

Answer 23

Nystagmus when abducting

Question 24

Internal ophthalmoplegia would result in lack of what functions?

Answer 24

Inability to construct pupil, loss of light and accommodation reflexes

Question 25

What are possible etiologies associated with oculomotor paralysis?

Answer 25

Uncal herniation, PCA aneurysms, diabetes

Question 26

What is the most common ocular cranial nerve paralysis?

Answer 26

Abducens paralysis

Question 27

Bilateral ocular cranial nerve paralyses indicate what overlying issue?

Answer 27

CNS lesion

Question 28

Are ocular cranial nerve paralyses usually unilateral or bilateral?

Answer 28

Unilateral