Special Senses: Vision, Hearing and Vestibular

Question 1

T/F: There is a greater proportion of our brain devoted to vision than any other sense?

Answer 1

TRUE

multiple concurrent visual processes are ongoing continuously like:

1. conscious perception of visual image info
2. conventional visual reflexes
3. saccadic movements
4. regulation of sleep/wake

Question 2

A lesion to the optic nerve prior to the optic chiasm would result in what type of visual deficit?

Answer 2

blindness in the ipsilateral eye

Question 3

what are the functional implications to ipsilateral blindness?

Answer 3

1. poor depth perception
2. small visual field
3. far peripheral vision is impacted = difficulty with driving and other higher level tasks
4. potential musculoskeletal issues like pain from positioning to compensate

Question 4

compression of the optic chiasm would result in what visual defict?

Answer 4

binasal hemianopsia = loss of nasal fields bilaterally, temporal fields spared

Question 5

what are the functional implications of binasal hemianopsia?

Answer 5

trouble with near vision and any tasks that utilize that like reading

difficulty concentrating

difficulty with ADLS

**these pts can usually learn to compensate pretty well though

Question 6

a lesion to the optic chiasm would result in what visual deficit?

Answer 6

bitemporal hemianopsia = results in loss of temporal fields, nasal fields spared

Question 7

bitemporal hemianopsia is commonly seen with what type of injury?

Answer 7

pituitary tumors

Question 8

what are the functional implications of bitemporal hemianopsia?

Answer 8

it’s like having horse blinders on!

miss peripheral objects and trip on things

miss doors

common fall risk

Question 9

what do patients with bitemporal hemianopsia require?

Answer 9

prism glasses or other external aids to be safe on their feet

Question 10

a lesion to the optic tract after the optic chiasm results in what type of visual deficit?

Answer 10

homonymous hemianopsia = complete loss in affected region of binocular visual field

Temporal half of R/L visual field + nasal half of L/R visual field

Question 11

homonymous hemianopsia is common with what type of injury?

Answer 11

CVA

Question 12

what are the functional implications of homonymous hemianopsia?

Answer 12

difficulty seeing everything on one side

must teach pt to turn towards the side they are missing

Question 13

a lesion to the lower division of the optic radiations (in temporal lobe) results in what visual deficit?

Answer 13

upper quadrantopia

Question 14

what are the functional implications for someone with upper quadratanopia?

Answer 14

none really!

just mostly annoying to pts but they can function just fine

Question 15

a lesion to the upper division of the optic radiation (temporal lobe) would result in what visual deficit?

Answer 15

lower quadrantanopia

Question 16

what are the functional implications of lower quadrantanopia?

Answer 16

might just be an annoyance and pt can function/adapt just fine

BUT, pts often forget to compensate with this making tripping and falling more common

Question 17

what causes homonymous hemianopia with macular sparring?

Answer 17

a lesion to both division of the optic radiations

or a lesion to the visual cortex

Question 18

what are the functional implications to homonymous hemianopsia with maccular sparring?

Answer 18

the exact same as homonymous hemianopsia

Question 19

what is the typical cause of monoaural hearing loss?

Answer 19

peripheral lesion/damage

cochlear lesion or damage to CN VIII

Question 20

what does having 2 ears help us with?

Answer 20

localization of source of sound

Question 21

what are some common causes of acquired hearing loss?

Answer 21

1. acoustic neuroma
2. meniere’s disease
3. traumatic brain injury
4. ototoxicity
5. presbycusis

Question 22

what are the functional implications of hearing loss?

Answer 22

can impact the ability to participate in social settings

but other than that none really/just annoying

Question 23

T/F: if there is acquired hearing loss, vestibular loss/dysfunction is usually not far behind

Answer 23

TRUE

Question 24

List the 3 vestibular reflexes

Answer 24

1. Vestibulo-occular reflex (VOR)
2. Vestibulospinal reflex (VSR)
3. Vestibulocollic reflex (VCR)

Question 25

what is the VOR?

Answer 25

allows us to stabilize gaze during head movements results in eye movements that equally coutner head movements

Question 26

describe how the VOR would work with L head turning

Answer 26

+L semicircular canals → +R abducens and +L occulomotor to move eyes -R semicircular canals → -L abducens and -R occulomotor

Question 27

Vestibular damage involving the VOR would most likely impact what structures?

Answer 27

1. Central: damage to midbrain and pons 2. Peripheral: CN VIII, labryinth structures

Question 28

damage to the VOR would result in what impairments?

Answer 28

1. difficulty stabilizing image on retina while head is moving 2. bilateral vestibular dysfunction 1. oscillopsia = bouncing vision 3. unilateral vestibular dysfunction 1. nystagmus 2. saccedes

Question 29

what do the VSR and VCR help with?

Answer 29

postural adjustments

Question 30

what structures are involved with the VSR?

Answer 30

1. otoliths (utricle and saccule) project to LVN 2. axons descend to antigravity muscles at all levels of the spinal cord

Question 31

what structures are involved with the VCR?

Answer 31

1. MVN axons descend in MLF to upper cervical levels of spinal cord * these help dictate head position in response to head rotation

Question 32

how does the VSR work?

Answer 32

Head is tilted to one side 1. Canals and otoliths are stimulated ipsilaterally (and inhibited contralateral) 2. Increased input through the vestibular nerve to the vestibular nuclei ipsilaterally 3. Impulses transmitted through the lateral & medial vestibulospinal tracts to the spinal cord \*\* result in increased lateral extension of trunk on side of head tilt, increased flexion contralaterally

Question 33

Damage to the VSR/VCR would result in what?

Answer 33

Postural instability, difficulty sensing falling/tipping Truncal ataxia

Question 34

what is truncal ataxia?

Answer 34

incoordination, unstable trunk movement during movement