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.
Question: Which way is horizontal? Which way is horizontal is a common question. Horizontal is left to right or east to west, or flat on the surface. Many people remember it by thinking about looking out over the horizon, which is flat, or goes from side to side, and horizon sounds like horizontal. Others look at the first letter H, and see how it has a line on either side indicating start and stop point, and then a flat line in between.