Visual field defects

Question 1

visual field defects - types

Answer 1

1. (right/left) anopia
2. Bitemporal hemianopia
3. (left/right) homonymous hemianopia
4. (left/right) upper quadrantic anopia
5. (left/right) lower quadrantic anopia
6. (left/right) hemianopia with macular sparing
7. Central scotoma

Question 2

Central scotoma is caused by

Answer 2

macular degeneration

Question 3

(right or left) anopia?

Answer 3

total blindness of left or right eye

Question 4

(right or left) anopia - mechanism

Answer 4

complete lesion of the right or left optic nerve

Question 5

bitemporal hemianopia?

Answer 5

vision is missing in the outer half of both the right and left visual field.

Question 6

bitemporal hemianopia is caused by

Answer 6

pressure exerted on the optic chiasm by a pituitary tumor

Question 7

(left or right) homonymous hemianopia is a

Answer 7

visual field loss on the left or right side of the vertical midline

Question 8

(left or right) homonymous hemianopia is caused by

Answer 8

1. a lesion in (left or right) of the left optic tract

2. a complete lesion in (left or right) of the left optic radiation

Question 9

(left of right) hemianopia with macular sparing is caused by

Answer 9

posterior cerebral artery occlusion (Lesion of the occipital cortex)

Question 10

left upper quadrantic anopia is caused by

Answer 10

1. partial involvement of the optic radiation (Meyer loop) by a lesion in the right temporal lobe
2. Middle cerebral artery stroke

Question 11

Mayer loop contains fibers from the

Answer 11

inferior retina (superior part of the visual field)

Question 12

Mayer loop pathway

Answer 12

through the temporal lobe by looping around the inferior horn of the lateral ventricle

Question 13

left lower quadrantic anopia is caused by

Answer 13

1. partial involvement of the optic radiation (dorsal optic radiation) by a lesion in the left parietal lobe
2. Middle cerebral artery stroke

Question 14

dorsal optic radiation

Answer 14

Fibers from the superior retina (inferior part of the visual field)

Question 15

dorsal optic radiation - pathway

Answer 15

takes shortest path (through the parietal lobe) via internal capsule

Question 16

Calcarine sulcus function

Answer 16

primary visual cortex (V1) is concentrated

Question 17

medial longitudinal fasciculus (MLF) is a

Answer 17

pair of tracts that allows for crosstalk between CN VI and the contralateral CN III nuclei

Question 18

medial longitudinal fasciculus (MLF) - function

Answer 18

it coordinates both eyes to move in same horizontal direction

Question 19

medial longitudinal fasciculus (MLF) - speed of communication (and mechanism and why)

Answer 19

highly myelinated –> to communicate quickly so eyes move at the same time

Question 20

medial longitudinal fasciculus (MLF) - highly myelinated

–>…

Answer 20

to communicate quickly so eyes move at the same time

Question 21

bilateral medial longitudinal fasciculus (MLF) - classically seen in

Answer 21

multiple sclerosis

Question 22

medial longitudinal fasciculus (MLF) - it coordinates both eyes to move in same horizontal direction - mechanism

Answer 22

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

Question 23

lesion in medial longitudinal fasciculus (MLF) –>

Answer 23

internuclear ophthalmoplegia (INO)

Question 24

internuclear ophthalmoplegia - mechanism

Answer 24

Lack of communication such that when CN VI nucleous activates ipsilateral lateral rectus, contralateral CN III nucleous does not stimulate medial rectus to fire, and the abducting eye gets nystagmous (CN VI overfires to stimulate III) –> the Convergense is normal

Question 25

internuclear ophthalmoplegia - the abducting eye gets nystagmous - mechanism

Answer 25

CN VI overfires to stimulate CN III

Question 26

directional term for internuclear ophthalmoplegia (e.g. right INO, left INO)

Answer 26

refers to which eye is paralysed

Question 27

internuclear ophthalmoplegia - convergence?

Answer 27

normal

Question 28

internuclear ophthalmoplegia usually implies

Answer 28

intrinsic brainstem disease

Question 29

MCC of unilateral internuclear ophthalmoplegia

Answer 29

stroke

Question 30

disease that can mimic a lesion of the medial longitudinal fasciculus

Answer 30

myasthenia gravis