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.
horizontal. 1  at right angles to the vertical; parallel to level ground. 2  flat or level: a horizontal position. 3  being in a prone or supine position; recumbent: His bad back has kept him horizontal for a week. 4  near, on, or parallel to the horizon. 5  of or relating to the horizon.