Neuro - Anat & Phys (Eye Applications Pt. 2)

Question 1

What is miosis? With what part of the nervous system is it associated?

Answer 1

Miosis (constriction [of pupil], parasympathetic)

Question 2

What is mydriasis? With what part of the nervous system is it associated?

Answer 2

Mydriasis (dilation [of pupil], sympathetic)

Question 3

What are the 1st and 2nd neurons involved in Miosis? Briefly describe the route each takes.

Answer 3

1st neuron: Edinger-Westphal nucleus to ciliary ganglion via CN III; 2nd neuron: short ciliary nerves to pupillary sphincter muscles

Question 4

What are the 1st, 2nd, and 3rd neurons involved in Mydriasis? Briefly describe the route each takes.

Answer 4

1st neuron: Hypothalamus to ciliospinal center of Budge (C8-T2); 2nd neuron: Exit at T1 to superior cervical ganglion (travels along cervical sympathetic chain near lung apex, subclavian vessels); 3rd neuron: Plexus along internal carotid, through cavernous sinus, Enters orbit as long ciliary nerve to pupillary dilator muscles

Question 5

Describe the pathway for the Pupillary light reflex and its consequence.

Answer 5

Light in either retina sends a signal via CN II to pretectal nuclei (dashed lines - in visual on p. 480 in First Aid 2014) in midbrain that activates bilateral Edinger-Westphal nuclei; Pupils contract bilaterally (consensual reflex)

Question 6

What can be observed clinically due to the Pupillary light reflex (if patient has normal reflex)?

Answer 6

Result: Illumination of 1 eye results in bilateral pupillary constriction

Question 7

What causes Marcun Gunn pupil? How does it present? How is it tested?

Answer 7

Marcus Gunn pupil (afferent pupillary defect) - Due to optic nerve damage or severe retinal injury. Decreased bilateral pupillary constriction when light is shone in affected eye relative to unaffected eye. Tested with the “swinging flashlight test”

Question 8

Draw a visual depicting the pupillary light reflex, including and labeling the following: (1) Edinger-Westphal nucleus (2) Ciliary ganglion (3) Light (4) Lateral gerniculate nucleus (5) Oculomotor nerve (6) Optic tract (7) Pretectal nucleus (8) Pupillary constrictor muscle.

Answer 8

See p. 480 in First Aid 2014 for visual in middle on the right

Question 9

In general, what are 2 major components of CN III, and where are they located in the nerve?

Answer 9

CN III has both motor (central) and parasympathetic (peripheral) components.

Question 10

Where does CNIII send its motor output? What category of disease primarily affects this, and why? Give an example of such a disease.

Answer 10

Motor output to ocular muscles - affected primarily by vascular disease (e.g., diabetes: glucose –> sorbitol) due to decreased diffusion of oxygen and nutrients to the interior fibers from compromised vasculature that resides on the outside of the nerve.

Question 11

What are 2 signs of CNIII motor damage?

Answer 11

Signs: ptosis, “down and out” gaze

Question 12

What part of CN III is first affected by compression, and why? Give 2 examples of such compression.

Answer 12

Parasympathetic output - fibers on the periphery are first affected by compression (e.g., posterior communicating artery aneurysm, uncal herniation)

Question 13

What is the major sign of CNIII parasympathetic damage?

Answer 13

Signs: diminished or absent pupillary light reflex, “blown pupil” often with “down-and-out” gaze

Question 14

What consequence/symptom is associated with Retinal detachment? What is the deficit, and what is its pathogenesis?

Answer 14

Separation of neurosensory layer of retina (photoreceptor layer with rods and cones) from outermost pigmented epithelium (normally shields excess light, support retina) –> degeneration of photoreceptors –> vision loss

Question 15

What are 3 causes to which retinal detachment may be secondary?

Answer 15

May be secondary to retinal breaks, diabetic traction, inflammatory effusions

Question 16

In what patient population are retinal breaks more common?

Answer 16

Breaks more common in patients with high myopia

Question 17

What often precedes retinal breaks?

Answer 17

Often preceded by posterior vitreous detachment (flashes and floaters) and eventual monocular loss of vision like a “curtain drawn down”

Question 18

How should retinal detachment be managed?

Answer 18

Surgical emergency

Question 19

What is age-related macular degeneration, and what 2 effects does it have?

Answer 19

Degeneration of macula (central area of retina). Causes distortion (metamorphosia) and eventual loss of central vision (scotomas)

Question 20

What is the difference between dry and wet age-related macular degeneration? How prevalent is each type?

Answer 20

Dry (nonexudative, > 80%); Wet (exudative, 10-15%)

Question 21

What characterizes Dry age-related macular degeneration?

Answer 21

Dry (nonexudative, > 80%) - deposition of yellowish extracellular material in and beneath Bruch membrane and retinal pigment epithelium (“drusen”) with gradual decrease in vision.

Question 22

What are 2 substances used to prevent progression of dry age-related macular degeneration?

Answer 22

Prevent progression with multivitamin and antioxidant supplements.

Question 23

What characterizes Wet age-related macular degeneration?

Answer 23

Wet (exudative, 10-15%) - rapid loss of vision due to bleeding secondary to choroidal neovascularization.

Question 24

What are 2 treatment options for wet age-related macular degeneration?

Answer 24

Treat with anti-vascular endothelial growth factor injections (anti-VEGF) or laser

Question 25

Draw the visual field defect (including Left and Right eyes) AND lesion associated with each of the following conditions: (1) Right anopia (2) Bitemporal hemianopia (pituitary lesion, chiasm) (3) Left homonymous hemianopia (4) Left upper quadrantic anopia (right temporal lesion, MCA) (5) Left lower quadrantic anopia (right parietal lesion, MCA) (6) Left hemianopia with macular sparing (PCA infarct), macula –> bilateral projection to occiput (7) Central scotoma (macular degeneration).

Answer 25

See p. 481 in First Aid 2014 for bottommost 2 visuals.

Question 26

What is associated with Meyer loop? What structure does it loop around?

Answer 26

Meyer loop - inferior retina; Loops around inferior horn of lateral ventricle.

Question 27

What is associated with the Dorsal optic radiation? Through which structure does it take the shortest path?

Answer 27

Dorsal optic radiation - superior retina; Takes shortest path via internal capsule.

Question 28

How is an image oriented when it hits the primary visual cortex?

Answer 28

Note: When an image hits primary visual cortex, it is upside down and left-right reversed

Question 29

What lesion can cause Bitemporal hemianopia? What structure can be affected to cause Bitemporal hemianopia?

Answer 29

Bitemporal hemianopia (Pituitary lesion, Chiasm)

Question 30

What lesion can cause Left upper quadrantic anopia? What vessel is associated with Left upper quadrantic anopia?

Answer 30

Left upper quadrantic anopia (right temporal lesion, MCA)

Question 31

What lesion can cause Left lower quadrantic anopia? What vessel is associated with Left lower quadrantic anopia?

Answer 31

Left lower quadrantic anopia (right parietal lesion, MCA)

Question 32

What infarct can cause Left hemianopia with macular sparing?

Answer 32

Left hemianopia with macular sparing (PCA infarct)

Question 33

What defect causes Central scotoma?

Answer 33

Central scotoma (macular degeneration)

Question 34

What kind of projection comes from the macula, and to what structure does it go?

Answer 34

Macula –> bilateral projection to occiput

Question 35

What is the Medial longitudinal fasciculus (MLF), and what function does it serve?

Answer 35

Medical longitudinal fasciculus (MLF): Pair of tracts that allows for crosstalk between CN VI and CN III nuclei. Coordinates both eyes to move in same horizontal direction.

Question 36

Describe and explain the level of myelination on MLF.

Answer 36

Highly myelinated (must communicate quickly so eyes move at same time).

Question 37

With what kind of condition are MLF lesions seen? Give a specific example.

Answer 37

Lesions seen in patients with demyelination (e.g., multiple sclerosis); Think: “MLF in MS”

Question 38

What disorder does a MLF lesion causes? Explain its presentation.

Answer 38

Lesion in MLF = INO (Internuclear ophthalmoplegia): lack of communication such that when CN VI nucleus activates ipsilateral lateral rectus, contralateral CN III nucleus does not stimulate medial rectus to fire. Abducting eye gets nystagmus (CN VI overfires to stimulate CN III). Convergence normal.

Question 39

Explain the directional term of INO (e.g., right INO, left INO).

Answer 39

Directional term (e.g., right INO, left INO) refers to which eye is paralyzed

Question 40

Explain what events related to MLF occur as a patient looks left.

Answer 40

When looking left, the left nucleus of CN VI fires, which contracts the left lateral rectus and stimulates the contralateral (right) nucleus of CN III via the right MLF to contract the right medial rectus.

Question 41

Draw a visual of MLF and its related pathway, including and labeling the following: (1) Nuclei of CN VI (on both sides) (2) Left MLF (3) Right MLF (4) Lateral recti (5) Medial rectus subnucleus of CN III (6) Medial recti.

Answer 41

See p. 482 in First Aid 2014 for visual on left

Question 42

Draw eyes depicting right INO. Label the following: (1) Which side has the MLF lesion? (2) Eye with Impaired adduction (3) Eye with Nystagmus (4) Direction of gaze.

Answer 42

See p. 482 in First Aid 2014 for visual on right