Hearing and balance

Question 1

You can differentiate true vertigo from other causes of “dizziness” by finding these two clinical findings:

Answer 1

Nystagmus and nausea/vomiting

Question 2

“right-beating” nystagmus means the fast phase is to the right or left?

Answer 2

Right

Question 3

A pt experiencing nystagmus sees the world spinning. Why is this?

Answer 3

Their brain is only processing images during the slow phase, thus they can essentially only see during the slow phase. If they have right-beating nystagmus, the slow phase is to the left, which makes the world look like it is spinning towards their right (or their head is spinning towards their left).

Question 4

The sacculus and utricle lie coplanar with which axises? (horizontal vs. verticle)

Answer 4

Sacculus- verticle

Utricle- horizontal

Question 5

This structure, found within the ampulla of the 3 semicircular canals is what detects changes in angular movements.

Answer 5

The cupula

Question 6

Crystals called otolith are found in the semicircular canals. What are they made of?

Answer 6

CaCO3 (calcium carbonate)

Question 7

In the ampullae of the semicircular canals, deflection of the hair cell cilia and kinocilia are towards or away from the kinocilia when generating an action potential (depolarization)? i.e towards –>iiI or away –>Iii

Answer 7

Towards —>iiI
to generate AP (depolarize cell)

Against—>Iii
to suppress AP (hyperpolarize cell)

Question 8

What channels open to cause depolarization of hair cells?

Answer 8

K+ channels

Question 9

The depolarization of hair cells causes K+ to move from the endolymph to the peripymph. How does this occur?

Answer 9

K+ channels open allowing K+ to flow from K+ rich endolymph into hair cell. Depolarization of hair cell opens Ca-dependent K+ channels that efflux K+ into basal side of hair cell that is seated in K+ poor perilymph.

Question 10

In the utricle, the kinocilia are facing toward or away from the striola (central valley)?

Answer 10

Toward

iiI iiI striola Iii Iii

Question 11

In the saccule, the kinocilia are facing toward or away from the striola (central valley)?

Answer 11

Away

Iii Iii striola iiI iiI

Question 12

Because of the orientation of the cilia in the saccule and its relative orientation to the surface of the earth when the head is facing forward, which cilia (upper or lower) would depolarize if you were standing in an elevator that moved UP.

Answer 12

Lower cilia would depolarize.
They are facing away from the striola and as the elevator ascends, they would be pushed down by the static otolithic membrane (towards their kinocilia), causing them to deoplarize.

Question 13

Are otoliths present on top of hair cells in the ampullae of the semicircular canals?

Answer 13

No

Question 14

You can think of the vestibular apparati as pushing or pulling the eyes?

Answer 14

Pushing.

Left vestibular apparatus is damaged, right pushes eyes left unopposed.

Question 15

This word represents the physical presentation of uneven tone on eyes by a damaged/weakened vestibular apparatus.

Answer 15

Nystagmus

Question 16

Your pt has left beating nystagmus. In which vestibular app. is the lesion?

Answer 16

Right vestibular apparatus lesion (fast phase beats AWAY from lesion. Slow phase beats TOWARDS lesion)

Question 17

What causes gaze evoked nystagmus?

Answer 17

NOT vestibular damage! You will NOT see vertigo!

• EtOH
• sedatives
• anti-convulsants

Question 18

You are testing whether or not your pt is in a true coma or a psychogenic coma. You irrigate the pt’s RIGHT ear. If your pt is in a TRUE coma, what will you see?

Answer 18

True coma means brainstem NOT communicating w/ vestibular nuclei. Brainstem does not sense “damage” to right vestibule “induced” by cold water irrigation.
- The pt’s “intact” left vestibular nucleus will “push” eyes towards “damaged” right side.
THERE WILL BE NO CORRECTIVE NYSTAGMUS towards left bc brainstem not intact to correct!

Question 19

You are testing whether or not your pt is in a true coma or a psychogenic coma. You irrigate the pt’s RIGHT ear. If your pt is in a PSYCHOGENIC coma, what will you see?

Answer 19

Psychogenic coma means brainstem IS communicating w/ vestibular nuclei. Brainstem senses “damage” to right vestibule “induced” by cold water irrigation.
- The pt’s “intact” left vestibular nucleus will “push” eyes towards “damaged” right side.
THERE WILL BE CORRECTIVE NYSTAGMUS towards left bc brainstem is “correcting” for “damage” pushing eyes to the right!

Brainstem—> correction by frontal eye fields in cortex

ONLY PSYCH pts will generate corrective (fast) saccades
Both have slow phase towards “side of damage”/cold water irrigation

Question 20

How fast can the CNS compensate for vestibular disturbances?

Answer 20

FAST days-weeks utilizing visual fixation. That’s why you may need Frenzel lenses to see nystagmus in pts who have CNS correction (visual fixation) for vestibular damage.

Question 21

If you have a central lesion such as MS or a stroke, can your CNS compensate for it with visual fixation?

Answer 21

NO

Question 22

Name the main drugs KNOWN to cause PERMENANT hearing/vestibular damage.

Answer 22

Cyotoxics (Cisplatin, Cyclophosphamide)
Aminoglycosides (-mycins)
maybe loop diuretics

Question 23

Name the 5 methods for unmasking compensated nystagmus.

Answer 23

Frenzel lenses
Head thrust- turning head TOWARDS side of lesion--> catch up saccade
Head shaking
Dix-Hallpike
Fundoscopy (obs. optic disk for shaking)

Question 24

Performing Dix-Hallpike on a BPPV pt will illicit nystagmus immediately or latently (5-20 seconds) after laying the pt down?

Answer 24

Latent: 5-20 secs. Cured w/ Epley maneuver

Central damage = NO LATENCY, NO IMPROVEMENT W/ REPETITIONS OF MANEUVER or Epley maneuver

Question 25

Which semicircular canal is occluded in BPPV?

Answer 25

Posterior

Question 26

Pts w/ BPPV will experience nausea only on movement or regardless of movement.

Answer 26

Only on movement.

- occlusion of canal = over stimulation of ampulla = brain thinks you are moving much faster than you actually are

Question 27

Vestibular neuritis is MCC by:

Answer 27

Viral infxn: HSV1 or Bell’s palsy

Question 28

How do you tx vestibular neuritis?

Answer 28

Benzos- decr. compensatory response
neclizine- decr. compensatory response
scopolamine - decr. compensatory response
Steroids to reduce inflammation

Question 29

How does vestibular neuritis present?

Answer 29

Vertigo + N/V

Gait veers towards affected side, bc you are looking over there!

Question 30

How do you differentiate cerebellar stroke from vestibular neuritis?

Answer 30

Head thrust in cerebellar stroke will be normal.

CT/MRI will be abnormal.