Vestibular System

Question 1

What vestibular fluid has similar composition to CSF?

Answer 1

Perilymph

Question 2

What movements are monitored by the semicircular canals?

Answer 2

Rotational head movements/Angular acceleration

Question 3

What movements are monitored by the utricle and saccule?

Answer 3

Translational head movements/linear acceleration

Question 4

What are the primary arteries supplying the vestibular system?

Answer 4

Labyrinthine A. (primary source) from AICA

Stylomastoid A.

Question 5

Where are the sensory receptors for the semicircular canals located?

Answer 5

Base of the ampulla

Question 6

What is the orientation of the receptors within the utricle and saccule?

Answer 6

Utricle - Longitudinal orientation

Saccule - vertical orientation

Question 7

What structure connects the saccule to the cochlea?

Answer 7

Ductus reuniens

Question 8

What disease is characterized by abnormal distention of membranous labyrinth?

Answer 8

Meniere’s disease

Question 9

What type of cells have a single, long kinocilium projecting from the apical surface? What is its function?

Answer 9

Hair cells with stereocilia

Vestibular sensory receptor

Question 10

What is the difference between a Type I and Type II hair cell?

Answer 10

Type 1: chalice shaped, surrounded by nerve calyx

Type II: Cyllindrical, innervated by nerve boutons

Question 11

In the ampulla, which hair cells are located more centrally and more peripherally in the crista?

Answer 11

Type I - centrally

Type II - peripherally

Question 12

What structure within the ampulla surrounds the hair cells and displaces them in the same direction as head movements?

Answer 12

Cupula (Displaced by endolymph)

Question 13

What structure displaces the hair cells in the macula?

Answer 13

Otolith membrane

Question 14

What movements displace the otoconia?

Answer 14

Changes in head position relative to gravity/linear acceleration

Question 15

Which vestibular nuclei are located in the superolateral pons?

Answer 15

Superior vestibular nucleus

Medial vestibular nucleus

Lateral Vestibular nucleus

Question 16

Which vestibular nuclei are found in the part of the medulla that makes up the floor of the 4th ventricle?

Answer 16

Medial vestibular nucleus

Lateral vestibular nucleus

Question 17

Which vestibular nuclei are found in the upper and lower medulla?

Answer 17

Medial vestibular nucleus

Inferior vestibular nucleus

Question 18

What side do the vestibular afferents project to?

Answer 18

Contralateral

Question 19

What structure do the primary vestibulocerebellar fibers travel through in the cerebellum and where do they terminate?

Answer 19

Inferior cerebellar peduncle

Terminate in Dentate Nucleus as mossy fibers

Question 20

Where do the secondary vestibulocerebellar projectsions come from? Where do they go?

Answer 20

Vestibular nuclei => fastigial and dentate nuclei

Question 21

What nuclei do the vestibulovestibular fibers arise from? What side do they connect with?

Answer 21

Superior and medial nuclei

The analogous contralateral nucleus

Question 22

What nuclei do the spinovestibular fibers provide input to?

Answer 22

Medial and lateral vestibular nuclei

Question 23

What is the reflex that achieves compensatory eye stabilization, allowing you to focus keep a fixed gaze on an object while the head is moving?

Answer 23

Vestibuloocular reflex

Question 24

What reflex is being suppressed so that you can focus your eyes on a moving target?

Answer 24

Vestibuloocular

Question 25

What vestibular structures are associated with vertical eye movements?

Answer 25

Vertical semicircular canals Saccule

Question 26

What vestibular structures are associated with horizontal eye movements?

Answer 26

Horizontal canals and utricle

Question 27

What vestibular structures are associated with torsional eye movements?

Answer 27

Vertical semicircular canals Utricle

Question 28

If you are focusing on an object and turn your head to the left? Which CN nuclei are activated? What is inhibited?

Answer 28

Activated: Ipsilateral CN III (oculomotor), contralateral abducens Inhibited: Ipsilateral abducens N.

Question 29

What is the linear vestibuloocular reflex?

Answer 29

Linear head movements result in linear eye movements in a direction equal to and opposite of the head movement Stabilizes gaze

Question 30

Describe the two phases of nystagmus.

Answer 30

Slow phase - vestibuloocular reflex directs eyes slowly in direction opposite to head motion Fast phase - Eyes rapidly spring back to central position to the same direction as the head (Named for direction of fast phase)

Question 31

How is the caloric test performed? What is a normal result?

Answer 31

Warm water - nystagmus beats toward ear which warm water was poured Cold water - nystagmus beats away from cold water Should be equal bilaterally

Question 32

What is an abnormal result of a caloric test?

Answer 32

Reduced/absent nystagmus ipsilaterally

Question 33

An unresponsive patient arrives in the ED. In order to evaluate the condition of the brainstem, you perform a Doll's Eyes maneuver. What result would indicate that the patient's brainstem was intact? What part of the brainstem?

Answer 33

Pt's eyes move in opposite direction of the head turn Reticular formation intact

Question 34

What laminae do the fibers of the vestibulospinal tracts terminate in?

Answer 34

Lamina VII to IX

Question 35

What vestibular tract terminates on the alpha and gamma motor neurons?

Answer 35

Laateral vestibulospinal tract

Question 36

Which vestibular tract monitors neck flexor and extensor motor neurons?

Answer 36

Medial vestibulospinal tract

Question 37

Where do the fibers of vestibular nuclei project and terminate? On what side?

Answer 37

Contralateral thalamic nuclei

Question 38

What are the areas of the vestibular cortex associated with primary somatosensory cortex?

Answer 38

Area 2v - sensations of whole body motion Area 3a - motor control of head and body

Question 39

What part of the vestibular cortex is the parietal cortex associated with?

Answer 39

Area 7

Question 40

What is the function of area 7 of the vestibular cortex?

Answer 40

Houses neurons involved in spatial coding, visual (optic flow), and vestibular motions signals Integrates cues of body motion in space (spatial awareness)

Question 41

What is the function of the insular area of lateral sulcus and Parietoinsular vestibular cortex (PIVC)?

Answer 41

Monitor body motion, somatosensory, proprioceptive, and visual motion stimuli

Question 42

PIVC lesions would result in what symptoms?

Answer 42

Episodes of vertigo, unsteadiness, loss of perception for "visual vertical"

Question 43

What is the function of the vestibular cortex portion of prefrontal cortex and superior frontal gyrus?

Answer 43

Receive vestibular signals Related to frontal eye field Controls saccades and smooth pursuit eye movements

Question 44

If a patient feels like he is spinning, but the environment around him is not, what is the most likely disorder?

Answer 44

Subjective vertigo

Question 45

If a patient feels like he is not spinning but that the room is spinning around him, what is his disorder?

Answer 45

Objective vertigo

Question 46

What type of vertigo would you see nystagmus? In what direction?

Answer 46

Objective vertigo Nystagmus beating in opposite direction to rotation

Question 47

What disorder results from cupulolithiasis? What happened?

Answer 47

Benign Paroxysmal Positional Vertigo *Probably* otoconia separated from the otolith membrane and became lodged in the cupula =\> abnormal cubula deflections when head changes position

Question 48

What does a Vestibular Schwannoma typically impinge upon?

Answer 48

CN VII, CN VIII, Labyrinthine A.

Question 49

Where is a Vestibular Schwannoma typically located?

Answer 49

Cerebellopontine angle/Internal acoustic meatus

Question 50

What can a Vestibular Schwannoma present with?

Answer 50

Hearing loss Gait difficulties Tinnitus

Question 51

Irritation of the vestibular ganglion from a virus can cause what disorder? What symptoms will a patient present with?

Answer 51

Vestibular neuritis Severe vertigo, nausea/vomiting (NO hearing loss)