Cranial Nerves III, IV, VI

Question 1

Eye Muscles and their Innervation

Answer 1

LR6 SO4
Lateral rectus - VI
Superior oblique -IV
All the others - III
Medial rectus, Inferior rectus, Superior rectus, Inferior oblique, Levator palpebrae

Question 2

Location of Abducens (SE) nucleus

Answer 2

Pontine tegmentum

Question 3

Where do the abducens rootlets exit?

Answer 3

anteriorly

Question 4

CN with longest intracranial course

Answer 4

Abducens

Question 5

Lesions of the abducens nerve

Answer 5

Diplopia at rest

Diplopia accentuated toward paralyzed side

Question 6

Diplopia

Answer 6

commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally

Question 7

Only the ________ _______ muscle can depress the eye when deviated medially

Answer 7

Superior oblique m.

Question 8

Location of Trochlear (SE) nucleus

Answer 8

Midbrain tegmentum

Question 9

Where do the Trochlear rootlets exit?

Answer 9

anteriorly

Question 10

True or False: The trochlear is seldom involved in isolated lesions

Answer 10

True

Question 11

Paralysis of Left Superior Oblique muscle

Answer 11

Unopposed action of inferior oblique muscle (left)
Produces diplopia
Diplopia is greatest when looking downward and
medialward
Head tilt reduces diplopia (right)

Question 12

Location of Oculomotor (SE and GVE) nuclei

Answer 12

Midbrain tegmentum

Question 13

Where do Oculomotor rootlets exit?

Answer 13

interpeduncular fossa

Question 14

Oculomotor n. (GVE) functional component

Answer 14

Edinger-Westphal nucleus; ciliary

ganglion

Question 15

Oculomotor n. (SE) functional component

Answer 15

Oculomotor nucleus
All extraocular muscles except SO and LR
Levator palpebrae muscle

Question 16

Accomodation for Near Vision

Answer 16

Ciliary muscle adjusts shape of lens

Pupillary constrictor muscles reduce size of pupil

Question 17

Convergence of Eye

Answer 17

Medial rectus muscles converge eyes
Lens thickens to accomodate for near vision
Pupil constricts to sharpen image

Question 18

Pupillary Light Reflex pathway

Answer 18

Retina; Optic nerve ->
Pretectum; Posterior commissure ->
Edinger-Westphal nucleus ->
Ciliary ganglion; Pupillary constrictor muscles ->
Direct and Consensual Reflex

Question 19

Lesion of Oculomotor n.

Answer 19

Affected eye:
Down and out
Dilated pupil

Question 20

Uncal Herniation

Answer 20

Supratentorial space-occupying lesion
Cerebral edema
Herniation of uncus
Compromise of CN III
      Pupillary dilation
      Reduced reaction to light
Confusion
Coma

Question 21

Abducens nucleus is a ________ nucleus

Answer 21

motor

Question 22

T or F: Abducens nucleus only includes motor neurons

Answer 22

False: Abducens nucleus also contains internuclear neurons

Question 23

Abducens internuclear neurons connect the abducens to the _____________ nuclear complex

Answer 23

Oculomotor

Question 24

Abducens nucleus controls eye movements in the

____________ plane

Answer 24

horizontal

Question 25

Loss of the abducens nucleus results in paralysis of _______ ____

Answer 25

Lateral Gaze

Question 26

Internuclear Ophthalmoplegia

Answer 26

a disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction. When an attempt is made to gaze contralaterally (relative to the affected eye), the affected eye adducts minimally, if at all. The contralateral eye abducts, however with nystagmus (involuntary eye movement)