CALORIC TEST

R1 Chang2003/10/02

History

Robert Barany in 1906, 1914 Nobel Prize

Fitzgerald and Hallpike(1942):biaural, bithermal caloric test, ocular fixation

Further modification: eye closure, eye open in the dark or behind Frenzel`sglasses, ENG recording

Computerized caloric test

Variant caloric tests: Bithermal test (the standard) Monothermal test -- a single large bolus of ice water

is given rather than two irrigations with hot and cold Air caloric -- air is used instead of water. Bilateral irrigation -- both sides are irrigated

simultaneously Balloon test -- a water filled balloon is used instead

of water. Ice water caloric -- used to confirm complete loss

Bithermal Caloric tests (1)

Bailey 3rd edition Supine and head elevated 30 degrees The EAC is irrigated directly with

250ml of water7 degrees above and below body temperature (30 and 44)for 30 secs

Bithermal Caloric tests (2)

Observation: Ocular movement 2 minutes, beginning with stimulation

(duration) Frequency Fixation suppression Slow-phase velocity Amplitude

Closed-loop system

A small, distensible balloon in the ear canal

For tympanic membrane perforation

Mechanism

a test of the lateral semicircular canals alone

By virtue of vestibulo-ocular reflex

VOR (Vestibulo-ocular reflex)

Semicircular canal-extraocuar muscle connection

Purpose: stabilize images on the retina during head movement

Horizontal canal VOR A simple 3 neuron reflex

VOR

A simple 3 neuron reflex

1: Scarpa`s ganglion 2: Vestibuar nucleus 3: Oculomotor nucleus

(C.N. III, IV, VI)

VOR

Vestibular nystagmus Slow phase: vestibular nuclei Fast phase: saccadic system

(parapontine reticular formation)

Thermoconvection

Barany, 1914 Thermal gradient Movement of the

intra-canicular fluid by convection

Mechanism

COWS

The cold stimulus causes nystagmus to the opposite direction

The warm stimulus causes nystagmusto the same direction

Tasking

Canal Paresis (CP)

Right-ear left-ear/total (R30+R44)-(L30+L44)/(R30,44L30,44)

100% It should be 25% or less

Directional Preponderance (DP)

Right-beating - left-beating/total (L30+R44)-(L44+R30)/(R30,44L30,44) 100%

It should be 35% or less

Results(suggestive of a central disorder)

Spontaneous or positional nystagmuswith normal caloric results

Direction-changing nystagmusindependent of stimulus changes

Failure of fixation suppression

Results(suggestive of a central disorder)

Bilateral reduced or absent caloric responses without a history of labyrinthine or middle ear disease

Abnormal saccade and pursuit results, especially with normal caloric results

Hyperactive caloric responses (loss of cerebellum-generated inhibition)

Results(suggestive of a peripheral disorder)

Unilateral caloric weakness Bilateral caloric weakness with a history

of labyrinthine disease or administration of ototoxic drugs

Fatiguing positional nystagmus Intact fixation suppression response Direction-fixed nystagmus

The End

Thank you!