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Neuro 2 > Week 1 Vestibular > Flashcards

Week 1 Vestibular Flashcards

1
Q

What are the major functions of the vestibular system?

A

a. Estimates body position and movement
b. Postural control
c. Control of eye movements

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2
Q

Describe the movements associated with pitch, yaw, and roll.

A

a. Pitch – yes head nod
b. Yaw – no head shake
c. Roll – lateral flexion L and R

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3
Q

What is the peripheral vestibular system tasked with?

A

a. Stabilize visual images on fovea of retina during head movement for clear vision
b. Maintain postural stability, especially during head movement
c. Spatial orientation information

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4
Q

How does the peripheral vestibular system complete its primary functions?

A

relay information about static and dynamic positions of head and neck

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5
Q

What does the bony labyrinth contain?

A

perilymphatic fluid and supportive connective tissue

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6
Q

What does membranous labyrinth contain?

A
  • endolymph fluid
  • vestibule (otolith organs - utricle and saccule)
  • 3 semicircular canals
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7
Q

What is the function of the otolith organs? What directions is each organ associated with?

A
  • Relay information: linear acceleration/deceleration of head/neck and static head position
    a. Utricle – detects movement in the HORIZONTAL plane
    b. Saccule – detects movement in the VERTICAL plan
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8
Q

Describe how the otolith organs detect movement

A
  • Gravity dependent motion sensitivity
    a. Movement of sterocilia TOWARDS kinocilium = EXCITATORY
    b. Movement of sterocilia AWAY from kinocilium = INHIBATORY
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9
Q

stereocilia and kinocilium location in utricle

A

i. Stereocilia on floor
ii. Kinocilium towards midline

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10
Q

stereocilia and kinocilium location in saccule

A

i. Stereocilia on medial wall
ii. Kinocilium towards lateral edges

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11
Q

What is the function of the semicircular canals? Name the canals.

A
  • Relay information about angular velocity of the head
  • Filled with endolymph
    a. Anterior
    b. Posterior
    c. Horizontal
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12
Q

What is the ampulla and what is its functional relevance?

A

a. Bulbous formation at the start or finish of each canal
b. Contains cupula which houses stereocilia – sensitive to angular movements only

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13
Q

Explain the relevance to the directional flow of endolymph fluid in the semicircular canals

A
  • Endolymph will move in the opposite direction of the head movement
    a. Head rotation  movement of endolymph in corresponding canal  movement of hair cells in ampulla  depolarization/ hyperpolarization
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14
Q

T/F: The ampulla is sensitive to angular and gravity dependent movements.

A

False - the ampulla is ONLY sensitive to angular movements

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15
Q

Define utriculopedal and utriculofugal cupular displacement. How does this concept’s impact change with each canal?

A

a. TOWARDS utricle = ultroculopedal cupular displacement
i. Horizontal canal = excitatory
ii. Anterior/posterior canal = inhibatory
b. AWAY from utricle = ultriculofugal cupular displacement
i. Horizontal canal = inhibitory
ii. Anterior/posterior canal = excitatory

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16
Q

What structures are sensitive to gravity dependent motion?

A

otolithic organs - utricle and saccule

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17
Q

Explain how the R and L semicircular canals are paired. What movement is each canal most sensitive to?

A

a. L anterior paired with R posterior
b. R anterior paired with L posterior
c. Turn head R = R horizontal excited and L horizontal inhibited

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18
Q

What is the major source of vascularization for the vestibular system?

A

a. Labyrinthine artery off of AICA (anterior inferior cerebellar artery)

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19
Q

What does the anterior vestibular artery supply?

A

a. Vestibular nerve
b. Utricle
c. Ampullae of anterior and horizontal SCC

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20
Q

What does the common cochlear artery supply?

A

a. Cochlea
b. Ampulla of posterior SCC
c. saccule

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21
Q

____ seconds of ischemia = cell death

A

15

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22
Q

generates eye movements that enable clear vision during head motion

A

a. Vestibulo-Ocular Reflex (VOR)

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23
Q

generates compensatory body movements to maintain head and postural stability

A

b. Vestibulospinal Reflex (VSR) - cats

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24
Q

acts on neck musculature to stabilize the head

A

c. Vestibulocollic Reflex (VCR) - chicken

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25
List the steps involved in the vestibular-ocular reflex.
i. + R horizontal semicircular canal  R vestibular nucleus  L abducens nucleus  L abducens nerve to contract L lateral rectus and R oculomotor nucleus (MLF) to oculomotor nerve to contract R medial rectus ii. - L horizontal semicircular canal  L vestibular nucleus  R abducens nucleus  R abducens nerve to inhibit R lateral rectus and L oculomotor nucleus (MLF) to oculomotor nerve to inhibit L medial rectus
26
List the steps involved in the vestibulospinal reflex.
a. Head tilts to side b. Ipsilateral SCC/otolith excitation c. ↑ Input from vestibular nerve  vestibular nuclei ipsilaterally d. MVST/LVST (medial/lateral vestibulospinal tract) descending drive to truncal muscles e. Increase lateral truncal extension ipsilaterally/increase truncal flexion contralaterally
27
Cervico-Ocular Reflex (COR)
i. Interacts closely with VOR ii. Eye movements driven by neck proprioceptors
28
Cervicospinal Reflex (CSR)
i. Changes in limb position driven by neck afferent activity
29
Cervicocollic Reflex (CCR)
i. Helps stabilize head on body ii. Afferent input caused by changes in neck position leads to contralateral reflexive contraction of appropriate neck muscles
30
What is the function of the central vestibular system?
a. Eye movement control for gaze stabilization during movement b. Postural control and movement – aid in maintaining muscle tone c. Spatial orientation d. Autonomic nervous system control
31
Major function of lateral nucleus
principle vestibular relay
32
Major function of medial nucleus
VOR and VSR relay
33
Major function of superior nucleus
VOR relay
34
Major function of inferior nucleus
cerebellar and reticular formation relay
35
function of lateral vestibulospinal tract
i. Head and body position in space ii. Walking upright iii. Righting and equilibrium reactions
36
function of medial vestibulospinal tract
i. Head movements ii. Integrating head and eye movements
37
intended vs actual movement/error correcting mechanism
b. Vestibulocerebellar tract
38
adaption of postural responses based on prior experiences i. Not having to adjust to when subway starts to move ii. Moving sidewalks
c. Cerebellar-cortical loop
39
What cortical areas are associated with vestibular function?
a. Parieto-Insular Vestibular Cortex (PIVC) b. Medial Superior Temporal Region c. Ventral Intraparietal Region
40
a. Parieto-Insular Vestibular Cortex (PIVC)
i. Visual, somatosensory, and vestibular integration ii. Optokinetic nystagmus
41
b. Medial Superior Temporal Region
i. Visuo-vestibular integration ii. Self-motion perception
42
c. Ventral Intraparietal Region
i. Spatial orientation ii. Proprioceptive, auditory, visual, tactile, vestibular integration
43
What are the components of an audiogram?
a. Auditory Asymmetry b. Retrocochlear Pathology c. Ear Canal and Tympanic Membrane integrity
44
What does auditory asymmetry indicate?
ii. Indicates possibility of peripheral vestibular or auditory nerve pathology
45
What is retrocochlear pathology?
i. Unilateral sensorineural hearing loss, impaired speech recognitions ii. Damage to CN 8, cerebellopontine angle or CN 8 nerve root
46
Explain the utilization of ENG and VNG.
a. ENG (extraocular muscles) – electrodes placed around eye to measure VOR via muscle activation b. VNG – video goggles to monitor eye movement and VOR
47
What is the purpose of caloric testing? Explain how the test works. What are considered normal and abnormal results?
a. Evaluates integrity of unilateral vestibular apparatus by SCC endolymph manipulation b. Inject cold (inhibitory) or hot (excitatory) water into ear while patient has visual blocking and watch for nystagmus to occur (normal) c. COWS: COLD water generates nystagmus in OPPOSITE direction, WARM water in the SAME direction d. No nystagmus or asymmetry means abnormal functional of vestibular system
48
What is the purpose of VEMP testing and how does it work? What are considered normal and abnormal results?
a. Measurement of otolith function – look at muscle reflexes in neck or eyes i. cVEMP – measurement of reflexive SCM ipsilaterally response to sound ii. oVEMP – measurement of reflexive inferior oblique (eye elevation) contralaterally to air or bone conducted sound b. Abnormal results i. No muscular response to sound or ii. Asymmetrical response
49
When might a rotational chair test be ordered? What are considered normal and abnormal results?
a. Used for bilateral vestibular hypo-dysfunction b. Normal – test creates nystagmus c. Abnormal – no VOR gain observed
50
Dizziness
i. Feelings of imbalance, spinning, and lightheadedness ii. Multiple causes
51
Vertigo
i. The room is spinning ii. Rotational or linear iii. Due to imbalance of tonic neural activity to vestibular cortex iv. Caused by peripheral or central vestibular damage
52
Oscillopsia
i. Gaze instability – environment is moving and shaking even though head is still ii. Bilateral > unilateral vestibulopathy, central vestibular dysfunction iii. ONLY occurs when eyes are OPEN
53
What can only occur when the eyes are open?
oscillopsia
54
What is the purpose of the Motion Sensitivity Quotient? What cutoff scores are available?
a. Position-dependent clinical exam – rate symptoms on 0-5 and track how long symptoms occur i. 0-30 = mild vestibular dysfunction ii. 11-30 = moderate vestibular dysfunction iii. 31-100 = severe vestibular dysfunction
55
What is the purpose of the Dizziness Handicap Inventory? What cutoff scores and other metrics are available?
a. Self-assessment to evaluate self-perceived handicap from dizziness i. Higher score = higher perceived handicap (0-100 scale) ii. 0-30 = Mild iii. 31-60 = Moderate iv. 61-100 = Severe 1. MCID = 18
56
Optokinetic movements
– involuntary, perceives motion in visual field and supplements VOR to stabilize vision i. Happens when watching a very visual dynamic scene ii. Combination of slow and fast paced eye movements
57
Nystagmus. how is it named?
– abnormal, bouncing eye movements back and forth (fast and slow phase) - named by direction of fast phase
58
Effect of fixation (lights on) on peripheral and central vestibular nystagmus
peripheral - nystagmus decreases central - nystagmus either does not change or increases
59
Direction of gaze on peripheral and central vestibular nystagmus
peripheral - mixed, horizontal and torsional central - single-plane horizontal, torsional or vertical
60
Effect of gaze on peripheral and central vestibular nystagmus
peripheral - nystagmus increases with gaze toward direction of quick phase central - nystagmus either does not change or reverses direction
61
vestibular nuclei projection to locus coeruleus for:
stress and panic
62
vestibular nuclei projection to nucleus of the solitary tract for:
vagus nerve: nausea
63
vestibular nuclei projection to area postrema for:
vomiting
64
vestibular nuclei projection to central nucleus of amygdala for:
emotional memory
65
vestibular nuclei projection to parabrachial nucleus for:
arousal
66
vestibular nuclei projection to infralimbic cortex for:
fear, emotional regulation
67
vestibular nuclei projection to hypothalamus for:
memory, BP, circadian rhythm

Neuro 2 (19 decks)

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