Week 7: Walsh style

What are the 4 functions of the vestibular nuclei?

1. sensory information about head movement and position relative to gravity

2. gaze stabilization

3. postural adjustments

4. autonomic function and consciousness

The vestibular system detects changes in __________

rate of motion vs. motion itself

acceleration/deceleration

What is the VOR?

• vestibular-ocular-reflex

• allows for eyes to move opposite of the head

• eyes can remain fixed on a point even if the head is moving

• contributes to gaze stabilization

Describe the anatomic arrangement of the three semicircular canals and their relationship to the horizontal plane

Describe the two otolithic organs

List the movements detected by the semicircular canals and otolithic organs

Describe the inhibitory visual-vestibular interaction in the cerebral cortex

List the structures constituting the peripheral and central vestibular systems

Explain the role of the vestibular system in motor control

Explain postural vertical disorder. List the three types of postural vertical disorder and give an example of each

Compare peripheral and central vestibular disorders and give examples of each

Diagram the vestibulospinal reflex and describe its function

Explain how to differentiate between vestibular, cerebellar, and sensory ataxia

Describe the indications and associated procedures for caloric testing, rotatory chair testing, and electronystagmography

Describe the effectiveness of rehabilitation for various vestibular pathologies

What is one way to differentiate between central dizziness from peripheral?

• person can’t find midline, likely central issue

• STROKE ALERT

Stroke of the _____ can present like _______

• PICA: posterior inferior cerebellar artery

• BPPV: benign paroxysmal positional vertigo

Receptors in the __________ detect movement of the head by ___________

• semicircular canals

• sensing motion of the endolymph

What is the cupula?

• gelatinous mass where hair cells are embedded

What causes the cupula to move and what is the resulting effect?

• fluid moves the cupula

• this causes hair cells attached to the cupula to bend

• hair cells change pattern of firing based on direction they are bent

Bending toward the tallest hair cell causes…

EXCITATION

Bending away from the tallest hair cell causes…

inhibition

A head turn towards the R results in… (what happens on either side of head)

• excitation of hair cells on the R side of the head (toward direction of turn)

• inhibition of hair cells on the L side of the head

Which canal are crystals most likely to get stuck in?

• posterior canal

Excitation of the posterior canal on the R causes _______ on the left _______

• inhibition

• L anterior canal

• RECIPROCAL SIGNS

What happens when signals from a pair of semicircular canals are NOT reciprocal?

• person will experience difficulties with control of posture, have abnormal eye movement, nausea

Information from the semicircular canals results in…

• stabilization of vision

• keeping eyes on target while head turns

If VOR does NOT occur, the issue is….

PERIPHERAL

True or false: otolithic organs are NOT sensitive to rotation

TRUE

What types of motion do otolithic organs respond to?

• linear acceleration/deceleration

What is the general process of otolithic organ function?

1. changing head position tilts the macula

2. weight of otoconia displaces gel mass causes bending of the hair cells

3. bending hair cells stimulates or inhibits hair cells based on direction of bend

   1. TOWARD = EXCITATION

   2. away = inhibition

4. determines frequency of firing of neurons in vestibular nerve

Information from the otolithic organs results in…

• adjustment of activity in LMN that innervate postural muscles

• ability to walk and stand and not have constant readjustment

What makes up the macula?

• hair cells that are enclosed in a gelatinous mass topped with calcium carbonate crystals in the utricle and saccule

The _______ is sensitive to horizontal movements whereas the ______ is sensitive to vertical movements

utricle: horizontal

saccule: vertical

In the NORMAL head position there is _______ in the utricle because…

• NO signal

• equal weight of crystals on hair cells so cilia remain straight

What causes ACTIVATION of hair cells in the utricle?

• acceleration

• head stays still but gel lags behind, bending the cilia

• bending of the cilia causes activation and action potential

When going _______ like in an elevator, hair cells in the ________ generate nerve impulses

• up/down

• saccule

What is the function of the vestibular nerve?

• to transmit info from the semicircular canals and otolithic organs to

  • vestibular nuclei in medulla and pons

  • flocculonodular node of cerebellum

Does a PICA stroke affect the peripheral vestibular system???

NO!!!

When vestibular activity increases, visual details are _______

suppressed

visual activity decreases

they are reciprocally inhibitory

If I spin around a bunch and then try to walk, why can’t I see very well?

• brain is processing too much vestibular input

• reciprocal inhibition of vestibular on visual information

• as a result vision is not accurate

What is the function of the vestibulospinal reflex?

• to generate compensatory body movements to maintain head and postural stability

• to prevent falling

What is the function of the vestibulocollic reflex?

• to keep the head steady on the neck

What are the two most common signs/symp of a vestibular disorder?

• vertigo

• pathologic nystagmus

How is nystagmus different in central lesions vs. peripheral?

• nystagmus is continuous, doesn’t fatigue

• also doesn’t change with position

What are traits of pathologic nystagmus in PERIPHERAL lesions?

• fatigable

• habituates

In PNS lesions, vertigo results from ______

position change!

What are typical signs of a peripheral vestibular disoder?

• recurring periods of vertigo

• moderate to severe nausea

• nystagmus that fatigues

What is the provoking stimulus for BPPV?

• head position change

Patient reports he has vertigo every time he looks over his shoulder while driving. Upon examination, you observe that nystagmus is present when turning his head to the side but it subsides within 2 minutes. What is his likely condition?

BPPV

Explain the pathophysiology of BPPV

• loose otoliths float into a semicircular canal

• quick head movements cause loose otolith to fall into a new gravity dependent position which causes abnormal fluid to flow into the canal

• this causes hair cells in cupula to be stimulated and send signals via vestibular nerve that head is moving when it’s actually stationary

crystals are not where they’re supposed to be so they cause abnormal stimulation of the cupula

What activities tend to provoke BPPV?

• getting in/out of bed

• bending over to look under bed

• reaching for something off a high shelf

• turning over in bed

• looking over shoulder while driving

What is the most common cause of BPPV?

• canalithiasis

  • displacement of otoconia from macula into a semicircular canal

What is cupulolithiasis?

• atypical form of BPPV

• otoliths attach to cupula

• need to shake pt’s head to get crystals free

Patient is experiencing the following symptoms: intense dizziness, nystagmus without latency, prolonged nystagmus when position is maintained, nystagmus non-fatiguable. What is the likely condition?

cupulolithiasis

Patient presents with the following symptoms: severe vertigo, nausea, unsteadiness, no change in hearing, spontaneous nystagmus. PT treatment is not helping. What is the likely condition?

vestibular neuritis

Patient presents with the following symptoms: vertigo, tinnitus, hearing loss, vomiting, sensation of fullness in ear. What is the likely condition?

Meniere’s disease

Patient presents with the following symptom: they describe the world as “bouncing up and down” what is the likely condition and name of the symptom they are experiencing?

• bilateral lesions of vestibular nerve

• oscillopisa

Will a patient with bilateral lesions of the vestibular nerve will present with vertigo and nausea? why or why not?

No

• vertigo results from asymmetry in sensory signals but with a bilateral lesion both sides are affected so there is no asymmetry

The _________ pathway from the vestibular nuclei has bilateral connections with nuclei of CN ___, ___, ___, and the _____, in order to influence eye and head movements

• medial longitudinal fasciculus

• CN 3,4,6

• superior colliculus

The _______ from the vestibular nuclei are both ____ and ________ and go to the ________ neurons that influence posture

• vestibulospinal tracts

• medial and lateral

• LMN

The __________ pathway from the vestibular nuclei goes to the nucleus of cranial nerve _______ to influence head position

• vestibulocollic

• cranial nerve XI, spinal accessory

The __________ pathways from the vestibular nuclei provide conscious awareness of _______ and ________ and input to the __________ tracts

• vestibulothalamocortical

• head position and movement

• corticospinal

The __________ pathways from the vestibular nuclei go to the ______ which controls the magnitude of muscle responses to vestibular information, including the ____________

• vestibulocerebellar

• vestibulocerebellum

• vestibulo-ocular reflex

The ________ pathways from the vestibular nuclei go to the _______ influencing the tracts and autonomic centers for _________

• vestibuloreticular

• reticular formation

• nausea and vomitting

The ______ vestibulospinal tract influences LMN to postural muscles in the limbs and trunk

lateral

The _______ vestibulospinal tract conveys signals that adjust ______ to upright via projections to _________

• medial

• head position

• cervical spinal cord

Describe the characteristics of postural vertical disorder and the subtypes (and which conditions they’re commonly seen with)

• person misperceives postural vertical

• they misalign their body relative to gravity

• lateropulsion: pushing body across midline to affected side

  • commonly seen with a stroke

• retropulsion: tendency to lean or walk backward

  • seen with Parkison’s diseae

• anteropulsion: tendnecy to lean or fall forward when walking

  • also seen with Parkinson’s disease and festering gait

What can cause a central vestibular disorder?

• damage to vestibular nuclei or connections within the brain

• result from

  • ischemia or tumors in brainstem/cerebellar region

  • cerebellar degeneration

  • MS

  • arnold-chiari malformation

How are symptoms with central vestibular disorders compared to peripheral?

• typically milder

Lesions of the vestibulothalamocortical pathway will cause…

• abnormal perception of vertical

• NO DIZZINESS OR VERTIGO

Patient presents with the following symptoms:

• dizziness and unsteadiness that persists for 3+ months

• dizziness worse with upright posture

• aggravated by motion of person, environment, visual demands

• they have anxiety

• recently they had a mild concussion (TBI)

what is the likely condition?

Persistent postural perceptual dizziness: 3D

Unilateral vestibular loss will present with what kind of symptoms? What is the pathophys?

• problems with posture

• eye movement control issues

• nausea

• signals from damaged side are not correctly balanced with signals from intact side

Unilateral vestibular loss affects the _________ system which causes a tendency to fall toward _______

• vestibulospinal

• side of lesion

Bilateral vestibular loss will present with what kinds of symptoms? What is the pathophys?

• difficulty walking in dark or on uneven surfaces

• NO VERTIGO

• oscillopsia: world seems to bounce

pathopys:

• bilateral loss of otolith input eliminates person’s internal sense of gravity

• person has to rely on visual and proprioceptive cues for spatial orientation

What are the main questions to ask a person when evaluating them for a vestibular system issue?

1. onset of symptoms

2. how long it’s been happening

3. what makes it better/worse

The following are characteristics of what type of ataxia:

• ataxic gait

• limb movements normal in supine

vestibular ataxia

The following are characteristics of what type of ataxia:

• ataxic gait regardless of if eyes are open or closed

cerebellar ataxia

The following are characteristics of what type of ataxia:

• impaired vibratory and position sense

• decreased or lost ankle reflexes

• lack of nystagmus and vertigo

• balance worse with eyes closed

sensory ataxia

In a ______ vestibular disorder, symptoms will fatigue

PNS

In a _______ vestibular disorder, symptoms will NOT fatigue even if _______

• CNS

• stimulus is removed