CALORIC TEST normal values
Timothy C. Hain,
MD • Page last modified:
February 21, 2021
See also: caloric_test• drugs effects•vendors•strabismus•blindness•instructions
The caloric test is a part of the ENG.
It is an attempt to discover the degree to which the vestibular system
is responsive and also how symmetric the responses are, between left and right ears.
It is a test of the lateral semicircular canals alone -- it does not assess
vertical canal function or otolithic function. While not as good as we would
like, the caloric test is the best that we have to deduce the function of each ear independently of the other.
Computations involved in the Caloric test: (see this page for the main procedure)
The main value derived from caloric testing is the peak slow-phase velocity, for each side and each temperature (i.e. 4 values). Four numbers are obtained -- cold right, cold left, warm right, and
warm left. Spontaneous nystagmus (SN) should be subtracted from these, and then the absolute value taken. From these responses, LC, LW, RC, RW, three additional numbers are derived:
- Total response -- absolute sum of all appropriately directed responses. TR= (RC+LC+RW+LW). The goal is to detect bilateral weakness. The total response should be 20 or greater. When responses are corrected for spontaneous nystagmus, the procedure here is to sum the absolute value of responses that go in the right direction - -i.e. left cold and right warm should be right-beating, right cold and left warm should be left beating. One should NOT sum the signed responses, as this would not be a good measure of bilateral weakness -- a perfectly symmetrical recording of very strong responses would work out to a TR of 0. It is usually enough to simply add the absolute value of all responses, and to change procedure only when a response goes the wrong direction.
- Directional preponderance -- right-beating - left-beating/total. It should be 35% or less. There is little if any clinical value in DP.
- Unilateral paresis or RVR (relative vestibular reduction), RVR = (RC+RW-LC-LW)/TR. This is called "Jongkee's formula". It should be 25% or less. If all responses are appropriately directed (see commentary on TR above), one can simply take the sum of the absolute values of responses due to the right ear, subtract the sum of the absolute responses due to the left, and normalize to the sum of the absolute values of all responses.
If spontaneous nystagmus is not subtracted off first, peculiar results may appear, such as greater than 100% paresis (which is obviously impossible).
Normal values for caloric tersting:
- Total responses less than 20 are often associated with bilateral vestibular
paresis (a rotatory chair test is needed for confirmation). Responses less than 10 are highly
suggestive of a bilateral reduction, such as due to gentamicin
toxicity. These are very conservative values. The mean TR is 129 while the lower 5th percentile for the TR is 27.48, and upper limit is 601 (Sills, Baloh et al. 1977). These values do not apply to air calorics as the response is generally less and the variability greater. We have never encountered an individual with more than 600 deg/sec total response. Because of the high variability of caloric tests, even absent caloric responses are sometimes encountered in otherwise normal individuals.This is the reason that rotatory chair testing is often needed. (Furman and Kamerer, 1989).
- Unilateral paresis > 40% is often associated with unilateral vestibular
paresis, such as due to vestibular
neuritis (there is no reasonable way of confirming a mild one). Paresis
between 25 and 40% is suspect for the reasons outlined below and should be
considered valid only if confirmed through other tests (i.e. Rotatory chair
testing, clinical data). Central vestibular lesions rarely cause severe caloric weakness because the root entry zone of the eighth nerve has a good vascular supply.
- Directional preponderance has little diagnostic meaning. A value > 35%
is abnormal using the 5th percentile criterion.
There is considerable test-retest variability. The upper limits for test-retest
variation for paresis were found by Proctor et al to be 24%. The upper limits
for DP was 22%. This suggests that upper limits of normal should be set at greater
than these values, which do not take into account variability of the normal
population, and are therefore inappropriately low.
Although difficult to decode due to presentation of logarithmically transformed data, the paper by Sills, Baloh et al. 1977 has considerable useful data concerning caloric parameters.
Effects of Age on Caloric testing. Very little.
According to Peterka et al (1990), "Caloric test parameters showed no consistent trend with age." This was also the opinion of Mallinson and Longridge, who stated "Our experiment confirms that slow phase velocity of caloric responses does not decline with age."
Karlsen et al (1981) reported a small decrease in the peak slow phase velocity, from 27.35 in individuals aged 18-35, and 25.95 in persons aged 71 and greater.
Maes et al (2010) found "increasing slow-component velocity values" with the caloric test with age. Their data (like all caloric studies) showed immense scatter and we suspect this finding was just due to insufficient power.
Mulch and Petermann reported middle aged persons had higher responses, but their study was done using older technology and we think that the newer papers should be favored as being more accurate.
- Bruner, A. and T. W. Norris (1971). "Age-related changes in caloric nystagmus." Acta Otolaryngol Suppl 282: 1-24.
- Maes, L., et al. (2010). "The effect of age on the sinusoidal harmonic acceleration test, pseudorandom rotation test, velocity step test, caloric test, and vestibular-evoked myogenic potential test." Ear Hear 31(1): 84-94.
- Mallinson, A. I. and N. S. Longridge (2004). "Caloric response does not decline with age." J Vestib Res 14(5): 393-396.
- Mulch, G. and W. Petermann (1979). "Influence of age on results of vestibular function tests. Review of literature and presentation of caloric test results." Ann Otol Rhinol Laryngol Suppl 88(2 Pt 2 Suppl 56): 1-17.
- Karlsen, E. A., et al. (1981). "The effects of age, sex, hearing loss and water temperature on caloric nystagmus." Laryngoscope 91(4): 620-627.
- Peterka, R. J., et al. (1990). "Age-related changes in human vestibulo-ocular reflexes: sinusoidal rotation and caloric tests." J Vestib Res 1(1): 49-59.