Special Senses: Vision, Hearing and Vestibular Flashcards
T/F: There is a greater proportion of our brain devoted to vision than any other sense?
TRUE
multiple concurrent visual processes are ongoing continuously like:
- conscious perception of visual image info
- conventional visual reflexes
- saccadic movements
- regulation of sleep/wake
A lesion to the optic nerve prior to the optic chiasm would result in what type of visual deficit?
blindness in the ipsilateral eye
what are the functional implications to ipsilateral blindness?
- poor depth perception
- small visual field
- far peripheral vision is impacted = difficulty with driving and other higher level tasks
- potential musculoskeletal issues like pain from positioning to compensate
compression of the optic chiasm would result in what visual defict?
binasal hemianopsia = loss of nasal fields bilaterally, temporal fields spared
what are the functional implications of binasal hemianopsia?
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
a lesion to the optic chiasm would result in what visual deficit?
bitemporal hemianopsia = results in loss of temporal fields, nasal fields spared
bitemporal hemianopsia is commonly seen with what type of injury?
pituitary tumors
what are the functional implications of bitemporal hemianopsia?
it’s like having horse blinders on!
miss peripheral objects and trip on things
miss doors
common fall risk
what do patients with bitemporal hemianopsia require?
prism glasses or other external aids to be safe on their feet
a lesion to the optic tract after the optic chiasm results in what type of visual deficit?
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
homonymous hemianopsia is common with what type of injury?
CVA
what are the functional implications of homonymous hemianopsia?
difficulty seeing everything on one side
must teach pt to turn towards the side they are missing
a lesion to the lower division of the optic radiations (in temporal lobe) results in what visual deficit?
upper quadrantopia
what are the functional implications for someone with upper quadratanopia?
none really!
just mostly annoying to pts but they can function just fine
a lesion to the upper division of the optic radiation (temporal lobe) would result in what visual deficit?
lower quadrantanopia
what are the functional implications of lower quadrantanopia?
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
what causes homonymous hemianopia with macular sparring?
a lesion to both division of the optic radiations
or a lesion to the visual cortex
what are the functional implications to homonymous hemianopsia with maccular sparring?
the exact same as homonymous hemianopsia
what is the typical cause of monoaural hearing loss?
peripheral lesion/damage
cochlear lesion or damage to CN VIII
what does having 2 ears help us with?
localization of source of sound
what are some common causes of acquired hearing loss?
- acoustic neuroma
- meniere’s disease
- traumatic brain injury
- ototoxicity
- presbycusis
what are the functional implications of hearing loss?
can impact the ability to participate in social settings
but other than that none really/just annoying
T/F: if there is acquired hearing loss, vestibular loss/dysfunction is usually not far behind
TRUE
List the 3 vestibular reflexes
- Vestibulo-occular reflex (VOR)
- Vestibulospinal reflex (VSR)
- Vestibulocollic reflex (VCR)
what is the VOR?
allows us to stabilize gaze during head movements
results in eye movements that equally coutner head movements
describe how the VOR would work with L head turning
+L semicircular canals → +R abducens and +L occulomotor to move eyes
-R semicircular canals → -L abducens and -R occulomotor
Vestibular damage involving the VOR would most likely impact what structures?
- Central: damage to midbrain and pons
- Peripheral: CN VIII, labryinth structures
damage to the VOR would result in what impairments?
- difficulty stabilizing image on retina while head is moving
- bilateral vestibular dysfunction
- oscillopsia = bouncing vision
- unilateral vestibular dysfunction
- nystagmus
- saccedes
what do the VSR and VCR help with?
postural adjustments
what structures are involved with the VSR?
- otoliths (utricle and saccule) project to LVN
- axons descend to antigravity muscles at all levels of the spinal cord
what structures are involved with the VCR?
- MVN axons descend in MLF to upper cervical levels of spinal cord
- these help dictate head position in response to head rotation
how does the VSR work?
Head is tilted to one side
- Canals and otoliths are stimulated ipsilaterally (and inhibited contralateral)
- Increased input through the vestibular nerve to the vestibular nuclei ipsilaterally
- 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
Damage to the VSR/VCR would result in what?
Postural instability, difficulty sensing falling/tipping
Truncal ataxia
what is truncal ataxia?
incoordination, unstable trunk movement during movement
