Neuroscience Week 5: Gaze Disorders

Question 1

Horizontal gaze centers location

Answer 1

Paramedian pontine reticular formation (PPRF)

Question 2

Vertical gaze centers location

Answer 2

Dorsal Midbrain

Question 3

VOR AKA

Answer 3

Vestibuloocular reflex

Question 4

PPRF AKA

Answer 4

Paramedian Pontine Reticular Formation

Question 5

The PPRF is controlled by?

Answer 5

Contralateral Frontal Eye Field in the frontal cortex

Question 6

Stimulation of the LEFT frontal eye field in the cortex will activate?

Answer 6

The RIGHT PPRF, which stimulate coordinated, simultaneous movement of both eyes to the right

Right lateral rectus

and

left oculomotor to stimulate medial rectus through the MLF

Question 7

Stimulation of the RIGHT frontal eye field in the cortex will activate?

Answer 7

The LEFT PPRF, which stimulate coordinated, simultaneous movement of both eyes to the left

Causes right oculomotor nerve to contract medial rectus through the MLF

and

simultaneous contraction of the left abducens lateral rectus

Question 8

MLF AKA

Answer 8

Medial Longitudinal Fasciculus

Question 9

Intranuclear opthalmoplegia (INO)

Answer 9

often the first symptom in MS!

Image is Left INO (disruption of the Left MLF)

Question 10

often the first symptom in MS!

Answer 10

Intranuclear Opthalmoplegia (INO)

Question 11

Left INO looking right

Answer 11

right eye Horizontal nystagmus on rightward gaze

left eye doesn’t move past midline on rightward gaze

Question 12

Right INO looking Left

Answer 12

Left eye Horizontal nystagmus on leftward gaze

right eye doesn’t move past midline on leftward gaze

Question 13

Common causes of IMO

3 listed

Answer 13

• Multiple Sclerosis
• pontine infarcts
• neoplasms involving the MLF

Question 14

Gaze disorders of gazing right

Answer 14

LEFT FEF drift toward side of lesion

LEFT frontal eye field drives right PPRF

Question 15

Lesion #1

Answer 15

Question 16

Lesion #2

Answer 16

Question 17

Lesion #3

Answer 17

Question 18

Lesion #4

Answer 18

Question 19

PPRF has unilateral/bilateral innervation

Answer 19

Mostly unilateral but has some bilateral innervation so overtime the unlesioned side can take over

Question 20

Question 1

Answer 20

C.

Question 21

if convergence is normal but there is the inability to adduct an eye during left or right gaze

Answer 21

Think MLF because convergence pathways are also in the dorsal midbrain so it is an INO

Question 22

PPRF

Question 23

Lesion in the left FEF involving left corticospinal tract, maybe MCA artery, will cause

Answer 23

eyes drift toward the side of the lesion and away from the weakness

Question 24

Lesion in the pons where the PPRF is, including corticospinals, will cause

Answer 24

eyes will drift away from the lesion and toward the side of the weakness

Question 25

Question 2

Answer 25

B.

Question 26

Vertical Gaze Center Location

Answer 26

Rostral midbrain thalamomesencephalic junction

Question 27

Parinaud’s Syndrome AKA

Answer 27

Dorsal Midbrain Syndrome

Question 28

Dorsal Midbrain Syndrome Clinical Presentation

Answer 28

• Impairment of vertical gaze, especially upgaze due to compression of the dorsal part of the vertical gaze center
• Light-near dissociation: Large, irregular pupils that do not react to light but to near-far accommodation. (due to disruption of optic tract fibers traveling to the EW nuclei via dorsal pathways)
• Bilateral
  Eyelid Retraction (Collier’s Sign)
• Convergence-retraction nystagmus: eyes rhythmically converge and retract in the orbits, especially on attempted upgaze

Question 29

Dorsal Midbrain Syndrome Common Causes

Answer 29

• Pineal Tumors
• Hydrocephalus

Question 30

Dorsal Midbrain Syndrome lesion location

Answer 30

Question 31

Question 3

Answer 31

B.

Question 32

Semicircular canals

Answer 32

Question 33

Vestibular nuclei and vestibular tracts

Answer 33

Question 34

Doll’s Eyes reflex

Answer 34

tests the integrity of the brainstem circuits in a comatose patient