02. Vestibular System (Dennis)

Question 1

What are the two types of hair cells?

Answer 1

Type 1 are chalice shaped and are surrounded by an afferent terminal called a nerve calyx. These are located more centrally on the crista ampullaris.

Type 2 are cylindrical and are innervated by synaptic boutons. These are located more laterally on the crista ampullaris.

Question 2

What is the origin of the afferent fibers to the vestibular apparatus?

Answer 2

The vestibular ganglion.

Question 3

Which way would you expect a patient to have nystagmus if you placed cold water in their left ear?

What about warm water in their right ear?

Answer 3

Cold water in the left ear shows right-beat nystagmus.

So does warm water in the right ear.

COWS: Cold water causes nystagmus that beats towards the Opposite side, Warm water beats towards the Same side.

Question 4

What laminae of the spinal cord recieve vestibular input from the medial and lateral vestibulospinal tracts?

Answer 4

Laminae VII, VIII, and IX

(7 , 8, 9)

Question 5

Which vestibular nuclei are associated with the lateral vestibulospinal tract?

What about the medial vestibulospinal tract?

Answer 5

Lateral vestibulospinal tract: lateral and inferior vestibular nuclei

Medial vestibulospinal tract: medial, as well as the lateral and inferior vestibular nuclei.

Question 6

What are the functions of Brodman area 2v and 3a?

Answer 6

They are in the primary somatosensory cortex.

2v: sensation of whole body motion
3a: integration of the motor control of the head and body

Question 7

Which portion of the vestibular apparatus detects torsional movements for the vestibuloocular reflex?

Answer 7

Vertical canal and utricle.

Question 8

What is the function of the insular areas of the lateral sulcus and parietoinsular vestibular cortex (PIVC)?

Answer 8

Responds to body motion, somatosensory, proprioceptive, and visual motion stimuli

Lesions cause vertigo and loss of perception

Question 9

What are the functions of Brodman area 7?

Answer 9

Involved in spatial coding, visual and vestibular motion signals

Integrates cues of body motion in space

Lesions result in confusion in spatial awareness

Question 10

What is the name of the disease associated with excessive pressure in the membranous labyrinth?

What are the symptoms?

Answer 10

Meniere’s Disease

This causes several symptoms:

Fluctuating hearing loss

Tinnitus

Vomiting

Nystagmus

Other vestibular sx.

Question 11

Which portion of the vestibular apparatus accounts for horizontal movements for the vestibulocular reflex?

Answer 11

The horizontal semicircular canals and utricle.

Question 12

What is the function of the medial vestibulospinal tract?

Answer 12

Vestibular stimulation of the neck muscles.

Question 13

Which portion of the vestibular apparatus detects vertical movements for the vestibulocular reflex?

Answer 13

Vertical semicircular canal and saccule

Question 14

How do hair cells detect motion?

Answer 14

The vestibular sensory receptors are hair cells with stereocilia that project from the apical surface. They all contain stereocilia and one long kinocilium. That kinocilium causes an activating signal when the stereocilia bend towards it, and an inhibitory signal when they bend away.

Question 15

Which portions of the vestibular apparatus is involved in the detection of translational movement?

Answer 15

The utricle and saccule.

Question 16

What two arteries supply the blood supply to the vestibular system?

Answer 16

The labyrinthine artery and the stylomastoid artery.

Question 17

How does the vestibular system coordinate movements between the right and left?

Answer 17

Vestibulovestibular fibers, which are collateral fibers between the right and left vestibular nuclei (left superior vestibular nucleus to right, and so on).

Question 18

What are the two different parts of the lateral vestibulospinal tract?

What are their functions?

Answer 18

Anterorostral areas: vestibular stimulation of the cervical spinal cord fibers.

Posterocaudal regions: vestibular stimulation of the lumbosacral cord.

Question 19

What are the vestibular functions of the prefrontal cortex and superior frontal gyrus?

Answer 19

Receive vestibular signals and are related to the frontal eye field.

Controls “saccades” and smoothes out eye movements.

Question 20

If the medial longitudinal fasciculus was cut, what muscle would not turn during the vestibulocular reflex?

Answer 20

The ipsilateral (to the turn) medial rectus.

If your head was turning left, your medial rectus would not pull your left eye to the right, because the fibers from the contralateral abducens to the ipsilateral oculomotor nucleus would be severed.

Question 21

What path do the primary vestibulocerebellar fibers take to reach the cerebellum?

Answer 21

The juxtarestiform body.

Question 22

What are the two types of vertigo?

Answer 22

Subjective vertigo: patient experiences the sensation of spinning while things

in the environment are not moving.

Objective vertigo: sensation is one of objects spinning while the patient is not

moving.

Question 23

BPPV

What “buzzword” is it associated with?

Answer 23

vertigo related to changes in body position, like turning over in bed, getting up from bed, bending over, etc.

cupololithiasis: crystals from the utricle separate form the otolith membrane and become lodged in the cupula of a semicircular canal

Question 24

Vestibular Schwannoma

Answer 24

benign tumor originating from schwann cells of the vestibular root

typically within the cerebellopontine angle impinging on structures in the acoustic meatus (CN VII, VIII and labyrinthine A.)

slow growin, may have hearing loss, gait issues, tinnitus

Question 25

Vestibular Neuritis

Answer 25

vertigo, N/V, NO HEARING LOSS or other CNS issues

possibly due to edema of the vestibular nerve or ganglion due to recent virus, such as HSV

may have recent history of viral infection

tx with antiemetics, vestibular suppressants, corticosteroids and antivirals

Question 26

COWs test in comotose pts

Intact brainstem:

Bilateral MLF Transection:

Lower Brainstem damage:

Answer 26

• No nystagmus is seen.
• With the brainstem intact, the eyes deviate to the side of cold irrigation
• With bilateral MLF transection, the abducting eye deviates to the side of cold​ irrigation.
• With lower brainstem damage to vestibular nuclei, the eyes do not deviate.