A study into the phenomenon of head-shaking nystagmus: its presence in a dizzy population.

In this paper we have prospectively analyzed results from approximately 1,500 patients who underwent a head-shaking test during routine electronystagmography (ENG). The incidence of head-shaking nystagmus (HSN) in a dizzy population was relatively high (31.7%) when compared to other so-called abnormalities in the routine ENG test battery. Its presence was also similar in both active vs. passive head-shake tests. When present, different types of HSN were identified (monophasic (76.8%), biphasic (22.7%) and triphasic (0.5%)). In some cases, reversals of the expected "normal" pattern occurred. A high correlation was found to exist between a positive head-shake test and the presence of spontaneous nystagmus, positional nystagmus and caloric test abnormalities.