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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
Q

List the steps involved in the vestibular-ocular reflex.

A

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

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26
Q

List the steps involved in the vestibulospinal reflex.

A

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

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27
Q

Cervico-Ocular Reflex (COR)

A

i. Interacts closely with VOR
ii. Eye movements driven by neck proprioceptors

28
Q

Cervicospinal Reflex (CSR)

A

i. Changes in limb position driven by neck afferent activity

29
Q

Cervicocollic Reflex (CCR)

A

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
Q

What is the function of the central vestibular system?

A

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
Q

Major function of lateral nucleus

A

principle vestibular relay

32
Q

Major function of medial nucleus

A

VOR and VSR relay

33
Q

Major function of superior nucleus

A

VOR relay

34
Q

Major function of inferior nucleus

A

cerebellar and reticular formation relay

35
Q

function of lateral vestibulospinal tract

A

i. Head and body position in space
ii. Walking upright
iii. Righting and equilibrium reactions

36
Q

function of medial vestibulospinal tract

A

i. Head movements
ii. Integrating head and eye movements

37
Q

intended vs actual movement/error correcting mechanism

A

b. Vestibulocerebellar tract

38
Q

adaption of postural responses based on prior experiences
i. Not having to adjust to when subway starts to move
ii. Moving sidewalks

A

c. Cerebellar-cortical loop

39
Q

What cortical areas are associated with vestibular function?

A

a. Parieto-Insular Vestibular Cortex (PIVC)
b. Medial Superior Temporal Region
c. Ventral Intraparietal Region

40
Q

a. Parieto-Insular Vestibular Cortex (PIVC)

A

i. Visual, somatosensory, and vestibular integration
ii. Optokinetic nystagmus

41
Q

b. Medial Superior Temporal Region

A

i. Visuo-vestibular integration
ii. Self-motion perception

42
Q

c. Ventral Intraparietal Region

A

i. Spatial orientation
ii. Proprioceptive, auditory, visual, tactile, vestibular integration

43
Q

What are the components of an audiogram?

A

a. Auditory Asymmetry
b. Retrocochlear Pathology
c. Ear Canal and Tympanic Membrane integrity

44
Q

What does auditory asymmetry indicate?

A

ii. Indicates possibility of peripheral vestibular or auditory nerve pathology

45
Q

What is retrocochlear pathology?

A

i. Unilateral sensorineural hearing loss, impaired speech recognitions
ii. Damage to CN 8, cerebellopontine angle or CN 8 nerve root

46
Q

Explain the utilization of ENG and VNG.

A

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
Q

What is the purpose of caloric testing? Explain how the test works. What are considered normal and abnormal results?

A

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
Q

What is the purpose of VEMP testing and how does it work? What are considered normal and abnormal results?

A

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
Q

When might a rotational chair test be ordered? What are considered normal and abnormal results?

A

a. Used for bilateral vestibular hypo-dysfunction
b. Normal – test creates nystagmus
c. Abnormal – no VOR gain observed

50
Q

Dizziness

A

i. Feelings of imbalance, spinning, and lightheadedness
ii. Multiple causes

51
Q

Vertigo

A

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
Q

Oscillopsia

A

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
Q

What can only occur when the eyes are open?

A

oscillopsia

54
Q

What is the purpose of the Motion Sensitivity Quotient? What cutoff scores are available?

A

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
Q

What is the purpose of the Dizziness Handicap Inventory? What cutoff scores and other metrics are available?

A

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
Q

Optokinetic movements

A

– 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
Q

Nystagmus. how is it named?

A

– abnormal, bouncing eye movements back and forth (fast and slow phase)
- named by direction of fast phase

58
Q

Effect of fixation (lights on) on peripheral and central vestibular nystagmus

A

peripheral - nystagmus decreases

central - nystagmus either does not change or increases

59
Q

Direction of gaze on peripheral and central vestibular nystagmus

A

peripheral - mixed, horizontal and torsional

central - single-plane horizontal, torsional or vertical

60
Q

Effect of gaze on peripheral and central vestibular nystagmus

A

peripheral - nystagmus increases with gaze toward direction of quick phase

central - nystagmus either does not change or reverses direction

61
Q

vestibular nuclei projection to locus coeruleus for:

A

stress and panic

62
Q

vestibular nuclei projection to nucleus of the solitary tract for:

A

vagus nerve: nausea

63
Q

vestibular nuclei projection to area postrema for:

A

vomiting

64
Q

vestibular nuclei projection to central nucleus of amygdala for:

A

emotional memory

65
Q

vestibular nuclei projection to parabrachial nucleus for:

A

arousal

66
Q

vestibular nuclei projection to infralimbic cortex for:

A

fear, emotional regulation

67
Q

vestibular nuclei projection to hypothalamus for:

A

memory, BP, circadian rhythm

Neuro 2 (19 decks)

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