Bilateral simultaneous caloric test for superior semicircular canal evaluation.

OBJECTIVE

To verify if the superior semicircular canal (SCC) can be stimulated using the modified "bilateral simultaneous caloric test" (BSCT).

STUDY

DESIGN

Prospective study in a tertiary care center.

METHODS

We performed a simultaneous irrigation of both ears with cold water at 24°C. Simultaneous irrigation of both ears inhibits the response of the horizontal SSC and avoids vegetative reaction. Modified BSCT was completed on 12 healthy individuals with no previous otologic history and on 12 patients with unilateral superior SCC obliteration for dehiscence syndrome using a middle fossa approach. Caloric response was recorded in 3 different positions (midline, head rotated to the right and then rotated to the left), and results were compared.

RESULTS

Nystagmus was vertical and upbeating. In the healthy population, the median intensity of nystagmus was 14.42 ± 7.32, 11, and 10.5 degrees per second for the 3 head positions. In the population with one obliterated superior SCC, the median intensity of nystagmus was 7.58 ± 3.8 degrees per second when the head was in the midline position, 6.0 degrees per second when the healthy superior SCC was stimulated, and 1.5 degrees per second when the obliterated canal was stimulated. Using a nonparametric statistical test, the mean intensity difference was statistically significant between the 2 populations (p < 0.001) and statistically significant between the obliterated and nonobliterated canals (p = 0.003).

CONCLUSION

This study shows that the superior SCC can be specifically stimulated in humans. Modified BSCT can stimulate the superior canal and can provide a good estimation of its stimulation intensity after the surgery.