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.
The subtropics are geographic and climate zones located roughly between the tropic circle of latitude at 23.5 latitude (the Tropic of Cancer and Tropic of Capricorn) and temperate latitudes (normally temperate latitudes refer to locations higher than 40 latitude).