45a - Balance, Dizziness, Vertigo

Question 1

What is the vasovagal reaction?

Answer 1

common fainting.

Question 2

If patient says room is spinning to the left, which way is the nystagmus?

Answer 2

fast beat of the nystagmus is also to the left and slow is to the right.

Question 3

If patient says room is spinning to left, which side is the lesion on?

Answer 3

if room is spinning to the left, nystagmus is to the left so slow phase is to the right, meaning right side is lesioned.

Question 4

What is rotation around the z axis called?

Answer 4

yaw

Question 5

How many degrees of freedom are there in standard human motion?

Answer 5

6. 3 translational and 3 rotational

Question 6

What structure is responsible for detecting angular movements?

Answer 6

semicircular canals with the ampulla (cupula)

Question 7

What structure is responsible for detecting translational movement in the horizontal axis?

Answer 7

utricle

Question 8

What structure is responsible for detecting translational movement in the vertical axis?

Answer 8

sacculus

Question 9

What are otholiths/otoconia?

Answer 9

crystals of calcium carbonate stuck in the membrane that distort the matrix when linear force movments occur.

Question 10

Describe the action potential of stereocillia in the vestibule

Answer 10

force can either open or close K+ on the kinocilium by moving them. If gravity opens the channels, K will flow in and depolarize the cell membrane, opening Ca channels, increasing intracellular Ca. Calcium will open Ca-dependent K channels that leak K into the perilymph

Question 11

What is the midline of the kinocilium called?

Answer 11

striola. This is the midline that the kinocilium of the utricle all face. In the sacculus they face away from it.

Question 12

What is a major difference between the sacculu/utricle and the cupula inside the ampulla?

Answer 12

the kinocilia of the cupula always point in one direction only, whereas the utricle and saccule have mirror images across the striola (pointing in opposite directions).There are also no otoliths in the hair cells of the semicircular canal.

Question 13

If you suddenly turn your head to the left, which vestibular canal will be stimulated and which direction should your eyes turn?

Answer 13

left horizontal semicircular canal will be stimulated and right canal will be inhibited. This will mediate a reflex movment of the eyes to the right to maintian visual fixation. AKA vestibulo-ocular reflex (VOR)

Question 14

What side should you administer cold water irigation to to ease the symptoms of a perosn with left beating nystagmus?

Answer 14

if it’s left beating nystagmus, eyes are slowly moving to right, so lesion is on the right. If you administer cold water to left, the eyes will pull back towards midline and symptoms will abate temporarily

Question 15

How does ice-water caloric testing differentiate psychogenic coma?

Answer 15

In true coma, there is a disconnect from the brainstem. When you do ice-water caloric testing, eyes will deviate towards irrigated side with no nystagmic corrections. If patient is in psychogenic coma, cortex recognizes mismatch between vestibular info and other sensory input so it directs eys back to midline with a nystagmus.TLDR: if ice water induces nystagmus = psychogenic coma

Question 16

What are Frenzel lenses

Answer 16

Nichols’ everyday glasses.20+ diopter lenses that block visual fixation and unmask compensated nystagmus.

Question 17

Which way is the eye moving if on fundoscopic exam you see the optic disc moving down?

Answer 17

eye is moving up if the disc is seen moving down.

Question 18

What is Dix-Hallpike maneuver?

Answer 18

turn head to right and fall back from sitting to lying position to maximally stimulate right posterior canal and maxiamlly inhibit left anterior canal.

Question 19

What is Nylan-Barany maneuver?

Answer 19

same as Dix hallpike except head is turned AS you lay donw. Tests the exact same information.

Question 20

How will a peripheral vertigo present on Dix-Hallpike maneuver?

Answer 20

nystagmus has 5-20 sec latency of onset after maneuver and subsides after 1-2 minutes.Nystagmus increases with gaze away from lesionUsually mixed horizontal.Repeated motion Habituates (gets better)

Question 21

How will central vertigo with nystagmus present on Dix-hallpike maneuver?

Answer 21

no latency of onsetsustained wihth positionno increase with change of gazeusually singl eplane nystagmusDoes NOT habituateprobably have other brainstem deficits

Question 22

What is pathology of bening paroxysmal positional vertigo?

Answer 22

calcium carbonate crystals called otoconia or otholiths that are usually embedded ina gelatinous membrane overlying the hair cells break free and enter semi-circular canals. During sleep they fall into posterior canal and plug it up, causing increased pressure and vertigo when laying down

Question 23

What is Epley maneuver?

Answer 23

??

Question 24

Which way will nysatgmus go if a person has BPPV in their right ear and they are doing a right Dix-hallpike?

Answer 24

normally right posterior canal would be activated and push eyes down so that field of vision remained fixed. However, BPPV will cause posterior canal to OVERREACT and will push eyes too far down. Nystagmus upward will result.

Question 25

What pathology can present in almost an identical manner as vestibular neuritis?

Answer 25

acute cerebellar stroke. You need to do a CT and MRI to exclude it. Head thrust will be normal, whereas it shoudl have catch-up saccades if it were vestibular neuritis