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/transverse plane plane parallel to the ground or horizontal surface; equally dividing superior and inferior areas; it lies at right angles to both sagittal and frontal planes. sagittal/median plane plane equally dividing left and right sides; it lies at right angles to both transverse and frontal planes.