Test 2: Eye movement CC

Question 1

**Vestibuloocular reflex is sensed by? **

Answer 1

Vestibular labyrinth. Senses **acceleration **

Question 2

**Optokinetic reflex is sensed by? **

**Afferent limb? **

Answer 2

• Movement of whole visual field. Senses **velocity. **
• **Stripes moved in from of subject to elicity nystagmus. Stimulation of WIDE-FIELD retinal ganglion cells sensitive to SLOW movements of receptive feild. **

Question 3

• **Strabismus- What is it? **
• **What can cause it? **

Answer 3

• Eyes are misaligned causing diplopia.
• May be due to misaligned pulleys (trochlear n?)

Question 4

How does the brain deal with constant diplopia?

Answer 4

Amblyopia- ignores input from one eye and doesn’t focus it. That way there isn’t any double vision.

Question 5

SX: Ipsilateral mydriasis and paralysis of accomodation

Answer 5

(Mydriasis= dilated pupil)

**Weber syndrome: **Lesion to oculomotor nerve= loss of preganglionic fibers

Question 6

**Contralateral hemiplegia, loss of abduction in ipsilateral eye. **

1. What’s the syndrome called? (What’s this “class” of disorders called?)
2. Where is the lesion
3. What could cause this lesion?

Answer 6

1. **Foville Syndrome. **This is an example of alternating hemiplegia and crossed deficit.
2. ALS and abducens damage in **caudal pons. **
3. occlusion of paramedian branches of basilar artery

Question 7

Right Eye: abducts when looking right, adducts when looking left

Left Eye: abducts when looking left, no change when looking right.

1. What’s this called
2. where’s the lesion?
3. What happens during convergence?

Answer 7

1. Internuclear ophthalmoplegia
2. MLF lesion between abducens nucleus and CN III
3. No deficits. Both eyes adduct.

Question 8

Abducens nucleus vs abducens nerve lesion

Answer 8

Lesion to nucleus= loss of medial rectus of contralateral eye during abduction, loss of lateral rectus of ipsilateral eye

Lesion to nerve= only loss to lateral rectus of ipsilateral eye.

Question 9

1.5 syndome=

Answer 9

MLF + abducens nucleus

Ipsilateral eye: doesn’t move in either direction for horizontal gaze

Contralateral eye: only abducts

Question 10

Horner’s syndrome

Answer 10

• ptosis, miosis (no dilator action), anhidrosis (no sweating)
• damage to sympathetic input (T1-T3 sympathetic trunk), ipsilateral cervical ganglion.

Question 11

What causes verticle gaze deficits?

Answer 11

Pinealomas pressing on posterior commisure.

Question 12

What does oblique saccades?

Answer 12

Combination of vertical and horizontal gaze centers.

Question 13

Why do Parkinson’s patients have spontaneous eye movement?

Answer 13

Unmodulated activity in nigrotectal pathway.

Question 14

What is the frontal eye field important for?

Answer 14

Voluntary and Memory-guided eye movements

Question 15

What is the superior colliculus impt for?

Answer 15

Reflexive orienting movements.

Question 16

1. Loss of superior colliculus=
2. Loss of FEF=
3. Loss of SC + FEF=

Answer 16

1. Few deficits after recovery
2. Few deficits after recovery (they compensate for eachother)
3. profound visuomotor impairment

Question 17

Smooth eye movement deficit caused by lesions in?

Answer 17

**floccular lesion (in cerebellum) **

Question 18

Pupillary light reflex

Answer 18

4 neuron arc

1. Retinal ganglion cells vis optic nerve==> optic tract==> midbrain==>
2. Olivary pretectal nucleus ==> projects BILATERALLY to
3. Edinger wesphal preganglionic nucleus==> preganglionic fibers exit via CN III==>
4. Ciliary ganglion ==> post ganglionic fibers to retina and excitiation of constrictor muscle

THE PURPOSE IS **MAINTAIN RETINAL ILLUMINATION **

Question 19

**tonic **dilated pupil=

Answer 19

Adie syndrome- damage to post ganglionic fibers leaving ciliary ganglion to innervate constrictor.

Question 20

What cells can respond to light?

Answer 20

1. Photoreceptors
2. Melanopsin containing ganglion cells (allos for pupillary light response even if they can’t “see” the light)

Question 21

Uneven pupil size=

Answer 21

aniscoria

Question 22

Uncal herniation

Answer 22

compression of CN III causing loss of superficial CN III fibers= pupillary fibers.

Question 23

Relative afferent pupillary defect

Answer 23

AKA marcus gunn pupil

Swinging light/alternating light test demonstrates that diseased eye has a slower and diminished response to light. Constriction time is also shortened.

Question 24

**Symptoms: **

• Small pupils with weak/absent pupillary light reflex bilaterally.
• Visual acuity is normal
• Constriction of pupils in near response

1. What is the disorder?
2. Where is the lesion?
3. What else do we know?

Answer 24

1. Argyll robertson pupil (often from tabes dorsalis)
2. Bilateral degeneration of olivary pretectal nuclei or their projections
3. Afferent and efferent limbs of light reflex are intact.

Question 25

Desire causes pupil dilation. What else could I do to make the pupils dilated?

Answer 25

Crack probably works. **cholinergic blockers. **

Question 26

Corneal blink reflex

Answer 26

Tests facial n and V1 V1--\> spinal trigeminal nucleus --\> facial motor (stimulatory) + inhibitory to CNIII levator palpebra

Question 27

WHY ARE YOU BLINKING SO MUCH AND SO FAST?

Answer 27

**blepharospasm=** disorder in rhthmic blinking behavior (12/min)

Question 28

You're eyes look dry and susceptible to lesions, please blink some more. (why isn't this person blinking)?

Answer 28

**Parakinosonism= **decreased blinking rate.

Question 29

Loss of blink reflex. No ptosis or loss of vertical gaze. Where's the lesion?

Answer 29

Facial nerve damage.

Question 30

Ptosis, loss of vertical gaze. Blink reflex is normal.

Answer 30

Oculomotor nerve lesion.

Question 31

Deer in headlights! (why does this happen)

Answer 31

Donno if it's for real in deer, but in humans... **Incrased sympathetic tone= superior tarsal activation**= wide eyes