A STUDY INTO THE PHENOMENON OF HEAD-SHAKING NYSTAGMUS - ITS PRESENCE IN A DIZZY POPULATION

In this paper we have prospectively analyzed results from approximatel y 1,500 Patients who underwent a head-shaking test during routine elec tronystagmography (ENG). The incidence of head-shaking nystagmus (HSN) in a dizzy population was relatively high (31.7%) when compared to ot her so-called abnormalities in the routine ENG test battery. Its prese nce 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 th e expected ''normal'' pattern occurred. A high correlation was found t o exist between a positive head-shake test and the presence of spontan eous nystagmus, positional nystagmus and caloric test abnormalities.