knee-jerk reaction. Fig. an automatic or reflex reaction; an immediate reaction made without examining causes or facts. With one of his typical knee-jerk reactions, he said no immediately, citing some moral argument that no one understood. See also: reaction.
What did you see when the patients head was rolled to the opposite side? In horizontal canal BPPV, you should have seen a direction change. When the horizontal nystagmus is geotropic, the BPPV is suspected to be canalithiasis, occurring on the side with the more intense nystagmus.
(or transit), a geodetic instrument for determining directions and measuring horizontal and vertical angles during geodetic work and topographic and mine surveying, in construction, and in other applications. Horizontal and vertical circles calibrated in degrees and smaller units are the main measuring devices in the theodolite.