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.
1. a flat or level surface. 2. Geom. a surface generated by a straight line moving at a constant velocity with respect to a fixed point. 3. an area of a two-dimensional surface having determinate extension and spatial direction or position: horizontal plane.