Part 15

Question 1

what vestibular systems are tested by calorics

Answer 1

horizontal SCC and superior vestibular nerve

Question 2

the temperature gradient in calorics generates what

Answer 2

cupullar deflections which mimic head movement thus activating VOR and generating nystagmus

Question 3

cool irrigation

Answer 3

ampulofugal (opposite)
inhibition
- nystagmus in opposite ear of water

Question 4

warm irrigation

Answer 4

ampulopetal (same)
excitation
- nystagmus in same ear as water

Question 5

what % of this process is gravity independent and what does that mean

Answer 5

10% means that in space we would still have excitation if nerve heated

Question 6

caloric irrigators

Answer 6

open loop water system
close looped water system *old, no longer made
air system

Question 7

caloric procedure

Answer 7

head at 30 degrees from horizontal (vertical position)
vision denied goggles
initial calibration performed
alerting task
precaloric search for spontaneous nystagmus (30 seconds to record without stimulation)
Bithermal irrigation (warm and cold)
irigation ends (40s water, 60s air) alerting task continues
Fixation with goggles removed (10-15 seconds)

Question 8

Bithermal irrigation temperatures and time

Answer 8

water +/- 7 for 40s
air +/- 13 for 60 sec

Question 9

when does response hit peak velocity (caloric)

Answer 9

60-90 seconds after irrigation and declines 10-15 seconds after peak

Question 10

what is the order of irigation

Answer 10

Rw-Lw_RC-LC

Question 11

waiting period between irrigation

Answer 11

5 mins (body temperature to return)

Question 12

unilateral caloric weakness is abnormal when

Answer 12

greater than 25%

Question 13

unilateral caloric weakness is positive when

Answer 13

in left ear

Question 14

unilateral caloric weakness is negative when

Answer 14

right ear

Question 15

what does unilateral caloric weakness usually tell us

Answer 15

peripheral lesion (can be neural)

Question 16

what side does the unilateral caloric weakness localize to

Answer 16

the side with lesion R ear if negative weakness, L ear if positive

Question 17

bilateral caloric weakness

Answer 17

no response or weak in bithermal test stop calculations
- all 4 less than 8 degrees/sec and total RE and LE are each less than 12 deg/sec

Question 18

hyperactive response criteria

Answer 18

check no artifacts perforation etc.
- when one or both ears are greater than 110 degrees (RC+RW or LC+LW)

Question 19

what does hyperactive response indicate

Answer 19

cerebellum lesion
- inhibition not functioning

Question 20

directional perponderance

Answer 20

should be less than 30% if greater its abnormal

Question 21

directional preponderance is positive

Answer 21

right beating stronger

Question 22

DP is negative

Answer 22

left beating stronger

Question 23

if DP is +/- 100% what does that tell us

Answer 23

lack of total caloric response in one direction

Question 24

what does DP tell us about side of lesion

Answer 24

nothing its non localizing

Question 25

2 types of DP

Answer 25

pre-existing nystagmus (baseline shift) 99% of cases
2. Gain asymmetry (1%)- where nystagmus is truly beating in 1 direction stronger than other

Question 26

fixation supression

Answer 26

ratio of nystagmus intensity before and after fixation

Question 27

fixation suppression greater than what % is abnormal

Answer 27

60%

Question 28

Fixation suppression of 0 means

Answer 28

fully supressed

Question 29

Fixation suppression greater than 100 means

Answer 29

enhanced and is a characteristic of central pathology

Question 30

lack of fixation supression indicates

Answer 30

possible central lesion
bilateral: cerebellar degeneration
unilateral: focal lesions of CPA